Effects of Lomerizine, a Calcium Channel Antagonist, on Retinal and Optic Nerve Head Circulation in Rabbits and Humans

Yasuhiro Tamaki, Makoto Araie, Yasuhiro Fukaya, Miyuki Nagahara, Asuka Imamura, Maiko Honda, Ryo Obata, and Ken Tomita

2ϩ PURPOSE. To investigate the effects of lomerizine, a Ca antag- head (ONH), in addition to increased intraocular pressure onist, on the ocular tissue circulation in rabbits and on the (IOP).1,2 Calcium antagonists, which are widely used for the circulation in the optic nerve head (ONH) and choroid in treatment of hypertension and coronary vascular diseases, re- healthy volunteers. duce tone in blood vessels by inhibiting Ca2ϩ influx, thus ETHODS ϭ ϭ causing relaxation of smooth muscle cells and increased re- M . Lomerizine (0.1 [n 10] or 0.3 [n 11] mg/kg) or 3–5 vehicle solution (n ϭ 11) was injected intravenously in ure- gional blood flow in several organs. Systemic administration of a calcium antagonist, such as nifedipine,6–8 nimodipine,9 or thane-anesthetized rabbits, and blood flow in the retina, cho- 10,11 roid, and iris-ciliary body was measured by the microsphere brovincamine, reportedly retards the progression of visual field damage, at least temporarily, in a subset of patients with method and that in the ONH by the H2 gas-clearance method (0.1 [n ϭ 6] or 0.3 [n ϭ 9] mg/kg or vehicle, n ϭ 6). Oral 5 mg normal-tension glaucoma (NTG). lomerizine or placebo was administered to volunteers (n ϭ 8) Lomerizine, a newly developed calcium antagonist, is clin- ically used as an oral antimigraine drug at 5 mg twice daily in in a crossover study, and in areas of the fovea and ONH, the 12 normalized blur (NB), a quantitative index of blood velocity, Japan. It selectively inhibits the constriction of cerebral arteries induced by various stimulants in vitro,13 and it increases was measured, together with blood pressure, heart rate, and 14 intraocular pressure (IOP), before and 1.5, 3, 6, and 9 hours cerebral blood flow in cats. Further, its effects on systemic after administration. blood pressure and heart rate are much weaker than its effects on the central nervous system and cerebral arteries in dogs,15 RESULTS. Blood flow in the rabbit retina increased significantly healthy volunteers,16 and patients with migraine.17 Thus, in in the lomerizine-treated group, but blood flow changed little ocular tissues, especially in the retina or optic nerve, lomeri- in the choroid or iris-ciliary body. Blood flow in the rabbit ONH zine might be considered a vasodilator without systemic hypo- also showed a significant increase in the lomerizine-treated tensive effects. In conscious rabbits, intravenous lomerizine group. In human studies, the NB obtained from the ONH (0.03–0.3 mg/kg) significantly increased blood velocity in the during the experimental period showed a small but significant ONH (measured by the laser speckle method) without signifi- increase in the lomerizine-treated group compared with the cantly changing systemic blood pressure.18 Further, in exper- placebo-treated group, but no significant intergroup difference iments using the hydrogen gas-clearance method, intravenous was detected in the NB obtained from the fovea or in blood lomerizine (0.1 and 0.3 mg/kg) significantly increased ONH pressure, heart rate, or IOP. blood flow and inhibited the endothelin-1–induced hypoper- CONCLUSIONS. Lomerizine increases blood velocity, and proba- fusion in this tissue.19 bly blood flow, in the ONH and retina in rabbits, and it also The apparent selectivity of lomerizine for cerebral arteries increases blood velocity in the ONH in healthy humans, with- raised our hopes that in the eye this drug’s vascular effect out significantly altering blood pressure or heart rate. (Invest might be selective for ocular neural tissues. Further, the rela- Ophthalmol Vis Sci. 2003;44:4864–4871) DOI:10.1167/ tive lack of effect on systemic blood pressure implies that iovs.02-1173 lomerizine is more suited for ophthalmic use than other calcium antagonists, although occasional sleepiness or flushing is 12 he development of several ocular disorders has been at- reported as systemic side effects. However, there have been Ttributed to an insufficient blood flow. Moreover, the de- no reports on its effect on the circulation in ocular tissues velopment of glaucomatous optic neuropathy may be associ- other than the ONH in experimental animals, nor are any ated with a compromised tissue circulation in the optic nerve reports available of its effect on ocular circulation in humans. In the present study, the effect of lomerizine on blood flow in the retina, choroid, and iris-ciliary body, as well as in the ONH, was evaluated in rabbits by using the microsphere From the Department of Ophthalmology, University of Tokyo method or the hydrogen gas-clearance method. In addition, the School of Medicine, Tokyo, Japan. time course of the changes induced by lomerizine in the Supported in part by Grant-in-Aid for Development Science Re- circulation of the retina and ONH was monitored in rabbits, by search (B) 01870364 from the Ministry of Education, Science, Sports, the laser speckle method to enable estimation of the duration and Culture of Japan. 20–23 Submitted for publication November 18, 2002; revised May 2 and of the effects. Finally, we used the laser speckle method to July 8, 2003; accepted August 5, 2003. examine the effects of oral lomerizine on the circulation in the Disclosure: Y. Tamaki, None; M. Araie, None; Y. Fukaya, None; ONH and choroid in healthy volunteers. M. Nagahara, None; A. Imamura, None; M. Honda, Kanebo (F); R. Obata, None; K. Tomita, None The publication costs of this article were defrayed in part by page MATERIALS AND METHODS charge payment. This article must therefore be marked “advertise- ment” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Drug Corresponding author: Yasuhiro Tamaki, Department of Ophthal- mology, University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo- For animal experiments, lomerizine (1-[bis(4-fluorophenyl)methyl]-4- ku, Tokyo 113-8655, Japan; [email protected]. (2,3,4-trimethoxybenzyl)-piperazine dihydrochloride) was supplied to an

Downloaded from iovs.arvojournals.org on 09/29/2021 IOVS, November 2003, Vol. 44, No. 11 Lomerizine and Ocular Circulation 4865

investigator (MH) by Kanebo (Osaka, Japan). It was dissolved in a 20% (in one group of rabbits) or vehicle solution (in another group) was dimethylacetamide solution containing 2% tartaric acid. The vehicle solu- given at the same dosage and in the same manner as in the microsphere

tion was supplied by the same company. Lomerizine was injected intra- experiment. FABPm; heart rate; arterial PO2,PCO2, and pH; and body venously at doses of 0.1 and 0.3 mg/kg in a volume of 0.1 mL/kg body temperature were measured before and 15 minutes after the injection, weight, which were chosen on the basis of previous reports.15,18,19 Hu- as has been described. man volunteers received either a placebo tablet or oral lomerizine (Mygsis; Laser Speckle Method. Tissue circulation in the ONH and Pharmacia and Upjohn, Kalamazoo, MI) at a dose of 5 mg.17 retina was evaluated by the laser speckle method. Details of this method have been published elsewhere20–22 and are given only brieﬂy Animal Experiments herein. An apparatus consisting of a fundus camera equipped with a diode laser (wavelength, 808 nm) was used for monitoring the ONH Microsphere Method. Japanese rabbits weighing 1.8 to 2.5 kg circulation.21,22 A second apparatus with the blue component of an were used and handled in accordance with the ARVO Statement for the argon laser (wavelength, 488 nm) was used for monitoring the retinal Use of Animals in Ophthalmic and Vision Research. General anesthesia circulation.20 The fundus, on which the laser beam was focused, was was induced by intravenous injection of 0.9 to 1.1 g/kg urethane. The observed by means of an infrared CCD camera. The scattered light was femoral artery was cannulated with a polyethylene catheter connected imaged on an image sensor of 100 ϫ 100 pixels, corresponding to a to a pressure transducer head for measurement of mean femoral artery ﬁeld of 0.62 ϫ 0.62 mm in the rabbit fundus, on which a speckle

blood pressure (FABPm) and a heart rate, and the animal was put in a pattern appeared. The difference was then calculated between the modiﬁed restraining box equipped with a heating pad. Arterial partial average speckle intensity and the speckle intensities for successive

pressure of O2 (PO2), partial pressure of CO2 (PCO2), and pH were scans of the image speckles at the pixels on the sensor plane. This checked before and 30 minutes after intravenous injection of lomeri- difference (expressed as a percentage of the average speckle intensity) zine or vehicle solution (pH/Blood Gas Analyzer, model 170; Corning was defined as normalized blur (NB). NB is approximately equivalent Glass, Corning, New York, NY), and body temperature was monitored to the reciprocal of the speckle contrast given by Fercher and Briers.25 with a rectal thermometer. IOP was measured with a calibrated appla- It is primarily a quantitative index of the tissue blood velocity, although nation pneumatonograph. it is also influenced by the number of blood cells in the sampling Blood flows in the retina, choroid, and iris-ciliary body were deter- volume,23 and it correlates well both with the blood flow determined mined by the colored-microsphere technique24 before and after intra- by the hydrogen gas-clearance method in the ONH26,27 and that deter- venous administration of lomerizine. Heparin (500 IU/kg) was admin- mined by the microsphere method in the retina.20 The results were istered intravenously to prevent clotting. A catheter was introduced displayed in a color graphic showing the two-dimensional variations in into the left ventricle through the ipsilateral internal carotid artery, and the NB level over the field of measurement. The average NB level in any 0.10 mL of a suspension of nonlabeled red microspheres (15 Ϯ 0.3 ␮L, chosen square or rectangular area within the measurement field was 7 10 spheres/mL; E-Z Trac, Los Angeles, CA) was injected into the left calculated and termed NBav. ventricle. A reference blood sample was obtained from the cannulated In experiments involving the use of this method, Japanese albino femoral artery. Withdrawal started at the time of injection and contin- rabbits weighing 1.8 to 2.5 kg were anesthetized as described earlier. ued until 60 seconds after the injection. Then, lomerizine solution at a The femoral artery was cannulated as described for measurements of

dose of 0.1 or 0.3 mg/kg (or its vehicle) was injected intravenously. At FABPm and heart rate, and the animal was put in a modiﬁed restraining

30 minutes after administration, a second microsphere injection was box equipped with a heating pad. Arterial PO2,PCO2, and pH were given, except that blue microspheres were used. IOP (in the eye checked before and 30, 60, and 90 minutes after the injection of

contralateral to the carotid cannulation); FABPm; heart rate; arterial lomerizine or vehicle solution, and body temperature was monitored. PO2,PCO2, and pH; and body temperature were monitored as described In each eye, the pupil was dilated as described earlier. For measure-

earlier. The rabbit was then killed with intravenous pentobarbital ment of ONH tissue blood velocity, the NBav in one randomly chosen sodium, and the eye was enucleated and fixed in 4% formaldehyde for eye was recorded over a square area of 0.42 ϫ 0.42 mm (70 ϫ 70 1 hour. The fixed eyeball was bisected 2 mm posterior to the limbus, pixels in the sensor plane) within the ONH in which no discrete 21 and the retina and choroid were excised from the posterior half. The surface vessels were visible. Measurement of NBav was performed iris-ciliary body complex was excised and divided into the iris (with the every 0.125 second over a 1-second period,22 during which no eye iridial process) and the ciliary body and were blotted, weighed, and movement was encountered, using the apparatus equipped with a dissolved in 5 M NaOH solution. The dissolved tissues were passed diode laser.21 The values obtained during the 1-second measurement through a filter paper (2-␮m pore size; RAWG-02500; Millipore, Bed- period were further averaged, and the value so obtained is hereafter

ford, MA) and mounted on a glass slide. The number of microspheres referred to as NBONH. The absence of eye movements during the in samples on the slide was counted under a light microscope (Nikon, measurement period was confirmed by a method previously de- Tokyo, Japan) by a blinded examiner (YF). The blood sample was also scribed.20,21 Lomerizine solution was injected intravenously at a dose dissolved in NaOH solution, and the number of spheres counted. The of 0.3 mg/kg in a volume of 0.1 mL/kg body weight in one group of spheres injected before and after the lomerizine injection were distin- rabbits, with the same volume of vehicle solution being injected in guished by color, and the blood flows in the retina, choroid, and another group of rabbits treated in the same manner (control). The 24 iris-ciliary body were calculated in milligrams per minute. NBONH was recorded every 1 minute for the first 5 minutes, and then Hydrogen Gas-Clearance Method. Japanese albino rabbits every 5 minutes from 5 to 90 minutes after the injection. During the weighing 1.8 to 2.5 kg were anesthetized as described earlier. After the experiment, IOP in the eye contralateral to the NB measurement site pupil had been dilated with one drop of 0.4% tropicamide (Mydrin M; was measured with a calibrated applanation pneumatonograph before Santen Pharmaceutical Co., Osaka, Japan), a hydrogen electrode (plat- and 30, 60, and 90 minutes after the injection. inum needle with a 0.3-mm diameter Pt/Ir tip) was inserted through Dutch rabbits weighing 1.0 to 1.5 kg were used for NB measure- the vitreous body from the pars plana into the lower portion of the ments in the retina, because in this species the medullary area con- ONH to a depth of approximately 0.7 mm, under observation, with a taining retinal blood vasculature can be easily identified. After mydri- vitrectomy lens. A reference electrode was fixed in the subcutaneous asis in both eyes, the average NB level over a square retinal area of tissue of the animal’s head. Using a hydrogen gas-clearance flowmeter 0.62 ϫ 0.62 mm (100 ϫ 100 pixels in the sensor plane) that was free (RBF-222; Biomedical Science, Kanazawa, Japan), the capillary blood of visible surface vessels and approximately one papillary diameter flow in the ONH was calculated on the basis of the hydrogen density away from the ONH along the medullary rays was recorded in one half-life after inhalation of 4% hydrogen by mask at a rate of 5.0 L/min randomly chosen eye, using the apparatus equipped with an argon for 4 minutes. Calculations of blood flow were made before and 15 laser.20 With this apparatus, each measurement took 0.18 second, and

minutes after drug injection by a blinded investigator (AI). Lomerizine the average of three measurements was termed NBretina. General anes-

Downloaded from iovs.arvojournals.org on 09/29/2021 4866 Tamaki et al. IOVS, November 2003, Vol. 44, No. 11

TABLE 1. Blood Flow in Retina, Choroid, and Iris-Ciliary Body, before and 30 Minutes after Intravenous Administration of Lomerizine or Vehicle in Rabbits: Microsphere Experiment

n Retina Choroid Iris-Ciliary body

Vehicle Pre 11 24.3 Ϯ 23.5 1033 Ϯ 594 58.6 Ϯ 36.5 Post 25.4 Ϯ 12.9 1097 Ϯ 624 64.0 Ϯ 45.4 ⌬ 1.1 Ϯ 16.9 64 Ϯ 275 5.4 Ϯ 20.6 Lomerizine (0.1 mg/kg) Pre 10 12.0 Ϯ 5.7 1118 Ϯ 563 94.7 Ϯ 74.3 Post 19.5 Ϯ 12.3* 1097 Ϯ 522 103.1 Ϯ 65.5 ⌬ 7.5 Ϯ 8.2 Ϫ21 Ϯ 300 8.5 Ϯ 22.8 Lomerizine (0.3 mg/kg) Pre 11 26.1 Ϯ 15.6 1106 Ϯ 405 83.8 Ϯ 53.7 Post 47.5 Ϯ 29.8**† 1167 Ϯ 431 104.5 Ϯ 72.0 ⌬ 21.4 Ϯ 18.2‡‡ 60 Ϯ 202 20.7 Ϯ 59.4

Data are mean milligrams per minute Ϯ SD, with ⌬ indicating difference in blood ﬂow between baseline (Pre) and 30 minutes after (Post) injection of lomerizine (0.1 or 0.3 mg/kg) or vehicle. * P Ͻ 0.05; ** P Ͻ 0.01 versus corresponding Pre value (paired t-test). † P Ͻ 0.05 versus post value in vehicle group (Dunnett test). ‡‡ P Ͻ 0.01 versus difference (⌬) in vehicle group (Dunnett test).

thesia was induced, and monitoring of systemic parameters was per- no history of smoking, no systemic or ocular disease, and only mild formed as described earlier. The lomerizine or vehicle-solution injec- refractive errors, were selected. On any day on which measurements

tion and the NBretina and IOP measurements were performed in were to be taken, the participants did not drink coffee, tea, or alcohol, lomerizine and control groups as has been described. NB measure- and engaged in no strenuous exercise. ments were performed by a blinded investigator (KT). For baseline measurements on day 0, the pupil was dilated with one

drop of 0.4% tropicamide in the right eye. NBONH,NBfovea, and IOP in Human Study the right eye, brachial arterial blood pressure, and heart rate were NB Measurements in Human ONH and Fovea. Thirty measured at 08:00. A fundus photograph (Polaroid; Cambridge, MA) minutes before measurements were to begin, the pupil was dilated was taken to record the site of measurement. Measurements were with one drop of 0.4% tropicamide (Mydrin M; Santen Pharmaceutical). repeated 90, 180, 360 and 540 minutes after the initial measurement During the measurement, the subject was asked to watch a target light, (i.e., at 09:30, 11:00, 14:00, and 17:00). Five minutes after each mea- and an electrocardiogram was monitored simultaneously. Image speck- surement, one drop of 0.4% tropicamide was instilled into the right les were recorded from the measurement field, which was located on eye. On day 1, the same measurements were performed using the same the temporal side of the ONH and corresponded to a field of 0.72 ϫ time schedule as in the baseline experiment (day 0), except that the 0.72 mm (30° visual angle of the fundus camera). We obtained the subjects were randomly assigned to either the lomerizine- or placebo- average NB across the largest rectangular field within the measurement treated group. The former received oral 5 mg lomerizine (Mygsis; field that was free of visible surface vessels, and then further averaged Pharmacia & Upjohn), and the latter a placebo tablet, in each case just the values obtained over three cardiac pulses when fixation was satis- after the measurement at 08:00. From days 2 to 20, the subjects factory to give the mean NBav from the ONH (NBONH). The size of this received no drugs. On days 21 and 22, the same measurements were rectangular field varied among subjects because of the need to avoid performed on the same schedule as on days 0 and 1, except that the ϫ ϫ surface vessels, the range being from 0.22 0.29 mm (30 40 pixels) subjects received lomerizine or placebo just after the measurement at ϫ ϫ to 0.40 0.47 mm (55 65 pixels). Image speckles from the macular 08:00 on day 22, in a crossover manner. ϫ area, corresponding to a field of 1.06 1.06 mm (45° visual angle), Measurements were made by separate investigators blinded as to were recorded, and the NB s across a foveal area free of retinal vessels av the treatment: NB and NB (YT), IOP (MH), and arterial blood were further averaged (as described earlier) to obtain the mean NB ONH fovea av pressure and heart rate (RO). The results of the laser speckle measure- from the foveal area (NB ). In this case, the size of the field was fovea ments were digitally stored on magneto-optical disks as color maps 0.32 ϫ 0.32 mm (30 ϫ 30 pixels). from which NB and NB were determined by a blinded inves- Satisfactory fixation during the measurement period was confirmed ONH fovea tigator (MN). by a method previously described.20 It was further checked by inspect- Data Analysis. A paired t-test was used to compare values ing the color map and the time-course plot of NBav measurements taken every 0.125 second. When there was no eye movement during obtained in the same animals or humans, and an unpaired t-test or the measurement period, visible surface vessels did not change posi- Dunnett test to compare data between groups. Although NB is primarily a quantitative index of tissue blood velocity, it is also affected by the tion over the entire color map, and the time-course plot of NBav exhibited periodic fluctuations synchronized with the cardiac pulse.23 laser light-scattering properties of the tissue, and therefore it is not In contrast, when eye movement occurred, visible surface vessels over advisable to compare NB directly between drug-treated and control the entire color map changed position according to the eye movement. groups. Hence, the time-related change in NB after an injection was Experimental Protocol. The effects of a single dose of oral compared between the lomerizine- and vehicle-treated groups (using lomerizine on the circulation in the ONH and foveal area were studied data expressed as a percentage of the baseline). Baseline was defined in a group of healthy volunteers in a double-blind, placebo-controlled as the preinjection NB in the rabbit experiment, and as the NB ob- manner. The human study was approved by the Ethics Committee of tained at the same time on day 0 (for data obtained on day 1) or on day the University of Tokyo and was performed in accordance with the 21 (for data obtained on day 22) in the human experiment. An analysis ethical standards of the 1964 Declaration of Helsinki. Before they were of variance (ANOVA) was applied to data obtained by sequential admitted to the study, written consent was obtained from all volun- measurements, to allow us to analyze intergroup differences in the teers after the nature of the study had been fully explained and routine series of percentages obtained for NB. P Ͻ 0.05 was considered eye examinations completed. Eight subjects, 20 to 29 years of age, with statistically significant.

Downloaded from iovs.arvojournals.org on 09/29/2021 IOVS, November 2003, Vol. 44, No. 11 Lomerizine and Ocular Circulation 4867

TABLE 2. Systemic Parameters before and 30 minutes after Intravenous Administration of Lomerizine or Vehicle in Rabbits: Microsphere Experiment

Blood

Pressure Heart Rate PCO2 PO2 n (mm Hg) (beats/min) pH (mm Hg) (mm Hg) Body Temperature (°C)

Vehicle Pre 11 91.7 Ϯ 5.3 280 Ϯ 40 7.35 Ϯ 0.03 31.1 Ϯ 2.7 85.2 Ϯ 9.9 37.0 Ϯ 0.3 30 min 94.6 Ϯ 9.0 287 Ϯ 30 7.35 Ϯ 0.03 23.6 Ϯ 3.3 94.8 Ϯ 7.0 36.7 Ϯ 0.7 Lomerizine (0.1 mg/kg) Pre 10 88.6 Ϯ 12.0 287 Ϯ 16 7.31 Ϯ 0.03 32.4 Ϯ 4.4 87.9 Ϯ 12.0 37.2 Ϯ 0.6 30 min 86.4 Ϯ 8.5 289 Ϯ 16 7.34 Ϯ 0.03 26.2 Ϯ 4.7 92.5 Ϯ 10.1 36.8 Ϯ 0.9 Lomerizine (0.3 mg/kg) Pre 11 86.7 Ϯ 8.3 278 Ϯ 20 7.32 Ϯ 0.03 28.9 Ϯ 3.3 91.5 Ϯ 9.0 37.1 Ϯ 0.7 30 min 82.3 Ϯ 6.6 290 Ϯ 20 7.33 Ϯ 0.07 23.8 Ϯ 3.6 95.7 Ϯ 10.6 37.1 Ϯ 0.7

Data are expressed as the mean Ϯ SD.

RESULTS n ϭ 6) in the control group. It increased significantly at 15 minutes after intravenous administration of lomerizine at a Animal Experiments dose of 0.3 mg/kg (average increase, 17.8%; P ϭ 0.037, paired t-test) and tended to increase at 0.1 mg/kg (average increase, Rabbits in which data obtained for systemic parameters imme- 14.8%; P ϭ 0.065), but it showed no significant change after diately before the drug or vehicle injection were outside the administration of vehicle (Table 3). The difference in ONH 28 normal range were not included in the study, and animals in blood flow between baseline and 15 minutes after the injection which any of the systemic parameters showed an abnormal tended to be larger in the 0.3 mg/kg lomerizine-treated group change during the experiment were also excluded. On this than in the vehicle-treated group (Dunnett test, P ϭ 0.092). basis, 3 of 35 rabbits in the microsphere experiment and 2 of FABPm; heart rate; arterial pH, PCO2, and PO2; and body 23 rabbits in the hydrogen gas-clearance experiment had to be temperature showed no significant change from baseline at discarded, probably due to poor physical condition. In the 15 minutes after the administration of lomerizine or vehicle laser speckle experiment, no rabbits were excluded from the (Table 4). study. NB Measurements in ONH. Both before and during the Lomerizine (0.1 [n ϭ 10] or 0.3 [n ϭ 11] mg/kg) or vehicle ONH experiment, there was no significant difference between solution (n ϭ 11) was injected intravenously in urethane- the lomerizine (n ϭ 9) and control groups (n ϭ 9) in terms of anesthetized rabbits, and blood flow in the retina, choroid, and IOP or in any of the systemic parameters (Table 5). In the iris-ciliary body was measured by the microsphere method and lomerizine group, the FABPm tended to decrease just after drug that in the ONH by the hydrogen gas-clearance method (0.1 [n administration, but the decrease was not statistically significant ϭ 6] or 0.3 [n ϭ 9] mg/kg or vehicle [n ϭ 6]). (P ϭ 0.171, Fig. 1). Microsphere Experiment. The blood flows in the retina, As shown in Figure 1, the mean NBONH at the various choroid, and iris-ciliary body determined by the microsphere time-points was significantly different between the lomerizine technique before and 30 minutes after the administration of and control groups (ANOVA of repeated measurements, P Ͻ lomerizine (0.1 [n ϭ 10] or 0.3 [n ϭ 11] mg/kg) or vehicle (n 0.001 [group] P Ͻ 0.001 [group ϫ time]). ϭ 11) are shown in Table 1. In the vehicle-treated group, NB Measurements in Retina. Both before and during the baseline blood flows in these tissues were 24.3 Ϯ 23.5, 1033 Ϯ retina experiment, there was no significant difference between 594, and 58.6 Ϯ 36.5 mg/min, respectively. The retinal blood the lomerizine (n ϭ 10) and control groups (n ϭ 10) in IOP or flow increased significantly after administration of lomerizine at doses of 0.1 mg/kg (average increase, 62.5%; P ϭ 0.017, paired t-test) and 0.3 mg/kg (average increase, 82.0%; P ϭ TABLE 3. Blood Flow in Optic Nerve Head before and 15 Minutes 0.003), but it showed no significant change after vehicle ad- after Intravenous Administration of Lomerizine or Vehicle in Rabbits: ministration. The difference in retinal blood flow between Hydrogen Gas-Clearance Experiment baseline and 30 minutes after the injection was significantly larger in the 0.3 mg/kg lomerizine-treated group than in the n ONH Blood Flow vehicle-treated group (Dunnett test, P ϭ 0.008). In contrast, Vehicle blood flow showed no significant change in the choroid or Pre 6 110.2 Ϯ 32.3 iris-ciliary body after administration of lomerizine or vehicle, Post 113.9 Ϯ 33.6 and in these tissues the difference in blood flow between ⌬ 3.7 Ϯ 6.4 baseline and 30 minutes after the injection was not significant Lomerizine (0.1 mg/kg) between the 0.1 or 0.3 mg/kg lomerizine-treated and vehicle- Pre 6 114.8 Ϯ 61.0 Ͼ Ϯ treated groups (P 0.1), compared with baseline. FABPm; Post 132.2 72.0 ⌬ 17.4 Ϯ 17.9 heart rate; arterial pH, PCO2, and PO2; and body temperature showed no significant change at 30 minutes after administra- Lomerizine (0.3 mg/kg) Ϯ tion of lomerizine or vehicle (Table 2). Pre 9 100.6 33.3 Post 116.0 Ϯ 36.6* Hydrogen Gas-Clearance Experiment. The blood flow ⌬ 15.4 Ϯ 14.7 in the ONH determined by the hydrogen gas-clearance method before and 15 minutes after the administration of lomerizine Data are mean milliliters per minute per 100 grams of tissue Ϯ SD, (0.1 [n ϭ 6] or 0.3 [n ϭ 9] mg/kg or vehicle [n ϭ 6]) are with ⌬ indicating the difference in blood flow between baseline (Pre) shown in Table 3. The baseline ONH capillary blood flow and 15 minutes after (Post) injection of lomerizine or vehicle. averaged 110.2 Ϯ 32.3 mL/min per 100 g tissue (mean Ϯ SD, * P Ͻ 0.05 versus corresponding Pre value (paired t-test).

Downloaded from iovs.arvojournals.org on 09/29/2021 4868 Tamaki et al. IOVS, November 2003, Vol. 44, No. 11

TABLE 4. Systemic Parameters before and 15 Minutes after Intravenous Administration of Lomerizine or Vehicle in Rabbits: Hydrogen Gas-Clearance Experiment

Blood Body

Pressure Heart Rate PCO2 PO2 Temperature n (mm Hg) (beats/min) pH (mm Hg) (mm Hg) (°C)

Vehicle Pre 6 87.2 Ϯ 2.2 281 Ϯ 15 7.36 Ϯ 0.02 35.4 Ϯ 3.4 89.5 Ϯ 8.3 37.0 Ϯ 0.2 15 min 87.1 Ϯ 2.2 287 Ϯ 15 7.36 Ϯ 0.02 35.2 Ϯ 4.2 90.3 Ϯ 7.8 37.0 Ϯ 0.2 Lomerizine (0.1 mg/kg) Pre 6 88.8 Ϯ 2.7 287 Ϯ 17 7.38 Ϯ 0.02 37.3 Ϯ 6.9 86.9 Ϯ 2.9 37.0 Ϯ 0.2 15 min 86.4 Ϯ 6.1 293 Ϯ 15 7.38 Ϯ 0.02 36.4 Ϯ 6.1 86.2 Ϯ 4.4 36.9 Ϯ 0.2 Lomerizine (0.3 mg/kg) Pre 9 86.5 Ϯ 5.1 280 Ϯ 18 7.38 Ϯ 0.03 38.9 Ϯ 3.9 87.2 Ϯ 5.4 36.9 Ϯ 0.2 15 min 84.3 Ϯ 6.6 284 Ϯ 15 7.37 Ϯ 0.03 36.0 Ϯ 3.3 87.4 Ϯ 3.9 37.0 Ϯ 0.2

Data are expressed as the mean Ϯ SD.

in any of the systemic parameters (Table 6). In the lomerizine retinal (9–15 mg/min)20,29,30 and ONH (33.4–119 mL/min per 26,27,31–33 group, the mean FABPm tended to decrease just after drug 100 g) blood flow measured in normal rabbits by the administration, but the decrease was not statistically significant microsphere and hydrogen gas-clearance methods, respec- (P ϭ 0.065, Fig. 2). tively. Although blood flow rate in the rabbit retina and ONH As shown in Figure 2, the mean NBretina at the various time previously reported have a rather wide range when measured points was significantly different between the lomerizine and by these two methods, in the present study these methods Ͻ control groups (ANOVA of repeated measurements, P 0.001 were used to compare the difference in retinal and ONH blood Ͻ ϫ [group], P 0.001 [group time]). flow change in the same rabbit eye by using the identical Human Study setting when the lomerizine or its vehicle was administrated, so that the error for measurements would be minimized. In the Under treatment with lomerizine or placebo, the IOP, mean microsphere experiment, lomerizine at an intravenous dose of blood pressure, and heart rate showed no significant change 0.3 mg/kg significantly increased its blood flow in the retina in from the baseline, nor was there an intergroup difference at urethane-anesthetized rabbits at 30 minutes after administra- Ͼ any of the measurement points (paired t-test, P 0.1; Table 7). tion, but it had no such effect in uveal tissues (the choroid and As shown in Figure 3, the time course of the changes in iris-ciliary body). The microsphere method is not particularly NB was significantly different between the lomerizine and ONH useful for assessing blood flow in the ONH, because only a placebo groups (ANOVA of repeated measurements, P ϭ 0.031 ϭ ϫ small number of microspheres becomes trapped in this small [group], P 0.026 [group time]), but NBfovea showed evidence of no such significant intergroup difference. tissue. Hence, we also studied the effects of lomerizine on the ONH tissue circulation using the hydrogen gas-clearance method. In this experiment, lomerizine at an intravenous dose DISCUSSION of 0.3 mg/kg tended to increase blood flow in the ONH in The first part of the present study investigated the effects of urethane-anesthetized rabbits at 15 minutes after its adminis- systemic lomerizine (a calcium antagonist with less effect on tration. This result is consistent with a previous report showing blood pressure in normotensive humans) on the ocular circu- that 0.1 and 0.3 mg/kg lomerizine significantly increased ONH lation in rabbits and demonstrated that this drug favorably blood flow (as determined by the hydrogen gas-clearance 19 affects the circulation in ocular neural tissues (the retina and method) in halothane-anesthetized rabbits. These data indi- ONH) in this species. Baseline values of blood flow rate in the cate that lomerizine may selectively increase blood flow in rabbit retina (12.0–26.1 mg/min) and ONH (100.6–114.8 mL/ ocular neural tissues, including the retina and ONH, rather than min per 100 g) are compatible with the previously reported uveal blood flow.

TABLE 5. Systemic Parameters of Albino Rabbits before and after Lomerizine Administration in the Optic Nerve Head Experiment

Pre 5 Min 15 Min 30 Min 60 Min 90 Min

Lomerizine group IOP (mm Hg) 20.2 Ϯ 3.9 18.5 Ϯ 3.4 18.8 Ϯ 3.1 18.2 Ϯ 4.5 17.2 Ϯ 4.3 16.4 Ϯ 3.9 HR (beats/min) 293 Ϯ 39 290 Ϯ 22 295 Ϯ 37 304 Ϯ 34 305 Ϯ 31 311 Ϯ 31 pH 7.39 Ϯ 0.03 7.40 Ϯ 0.03 7.40 Ϯ 0.03 7.41 Ϯ 0.03 Ϯ Ϯ Ϯ Ϯ PCO2 (mm Hg) 35.4 4.6 34.7 1.5 34.6 3.5 33.6 3.6 Ϯ Ϯ Ϯ Ϯ PO2 (mm Hg) 79.8 10.2 85.7 9.1 85.4 5.1 86.3 6.2 BT (°C) 38.6 Ϯ 0.4 38.5 Ϯ 0.5 38.4 Ϯ 0.7 38.4 Ϯ 0.8 Control group IOP (mm Hg) 20.3 Ϯ 5.4 20.6 Ϯ 5.5 19.8 Ϯ 5.6 19.2 Ϯ 4.2 16.1 Ϯ 3.4 16.3 Ϯ 3.9 HR (beats/min) 277 Ϯ 48 277 Ϯ 56 287 Ϯ 53 287 Ϯ 50 283 Ϯ 46 284 Ϯ 48 pH 7.38 Ϯ 0.05 7.39 Ϯ 0.03 7.39 Ϯ 0.02 7.39 Ϯ 0.01 Ϯ Ϯ Ϯ Ϯ PCO2 (mm Hg) 38.3 3.0 35.3 5.0 34.2 5.5 34.8 5.2 Ϯ Ϯ Ϯ Ϯ PO2 (mm Hg) 79.0 3.8 86.6 6.6 91.2 4.5 92.8 5.9 BT (°C) 38.2 Ϯ 0.6 38.1 Ϯ 0.5 38.2 Ϯ 0.6 38.0 Ϯ 0.8

Data are mean Ϯ SD (n ϭ 9). HR, heart rate; BT, body temperature.

Downloaded from iovs.arvojournals.org on 09/29/2021 IOVS, November 2003, Vol. 44, No. 11 Lomerizine and Ocular Circulation 4869

FIGURE 1. Time course of changes in NBONH and mean blood pressure in rabbits after injection of lomerizine (0.3 mg/kg) (F) or vehicle (E). FIGURE 2. Time course of changes in NBretina and mean blood pres- Ϯ F Mean SD in nine rabbits in each plot. Intergroup difference in NBONH sure in rabbits after injection of lomerizine (0.3 mg/kg) ( ) or vehicle (expressed as a percentage of baseline) was signiﬁcant (ANOVA) for (E). Mean and SD in 10 rabbits in each plot. Intergroup difference in data obtained by sequential measurements (treatment, P Ͻ 0.001; NBretina (expressed as a percentage of baseline) was signiﬁcant treatment ϫ time, P Ͻ 0.001). (ANOVA) for data obtained by sequential measurements (treatment, P Ͻ 0.001; treatment ϫ time, P Ͻ 0.001).

The NB obtained by the laser speckle method is primarily a than in the control group at 5 to 20 minutes after drug admin- 20,21,25 quantitative index of tissue blood velocity. When in istration, whereas NBretina was significantly greater in the rabbits the ocular blood flow was artificially changed by a lomerizine group than in the control from 5 to 90 minutes. The variety of means—by increasing the IOP,20,21 inhalation of 10% microsphere experiments indicated that lomerizine is less ef- 26 CO2, intravenous injection of a small amount of endothelin- fective on the short posterior ciliary arteries (choroidal circu- 1,26 or intravenous administration of calcium antago- lation) than on the retinal arteries. Circulation in the prelami- nists27,35—the NB value showed a good correlation with the nar-to-laminar part of the optic nerve, which is mainly supplied blood flow determined by the microsphere method in the by the short ciliary arteries, may show characteristics interme- retina or choroid20,21,35 and with the blood flow in the diate between those of the retinal and choroidal circulations, ONH26,27 determined by the hydrogen gas-clearance method and this may at least partly explain the less prolonged effect of

(in which a hydrogen electrode was inserted into the ONH lomerizine on NBONH. Blood ﬂow in both the surface area and tissue to a depth of approximately 0.7 mm, as in the present the prelaminar-to-laminar part of the ONH is thought to be

study). reﬂected in NBONH measurements made using the laser speckle In our laser speckle experiment in rabbits, lomerizine (0.3 method.19,26,27 The less prolonged effect of lomerizine on

mg/kg intravenously) signiﬁcantly increased blood velocity in NBONH could also be partly attributable to the surface area of both retinal and ONH tissue. However, both the amplitude of the ONH being nourished by the retinal circulation, whereas the effect and its duration were more prominent on the former the prelaminar-to-laminar part of the ONH is supplied by the than on the latter tissue, consistent with those obtained using short ciliary arteries. A similar explanation may be also appli- the microsphere and hydrogen gas-clearance methods, respec- cable to a signiﬁcant but not remarkable effect of oral lomer-

tively. NBONH was signiﬁcantly greater in the lomerizine group izine on the human ONH circulation presently recorded.

TABLE 6. Systemic Parameters of Dutch Rabbits before and after Lomerizine Administration in the Retina Experiment

Pre 5 Min 15 Min 30 Min 60 Min 90 Min

Lomerizine group IOP (mm Hg) 14.7 Ϯ 6.1 13.4 Ϯ 4.2 12.8 Ϯ 5.2 13.1 Ϯ 5.5 11.1 Ϯ 4.4 11.2 Ϯ 3.2 HR (beats/min) 274 Ϯ 18 269 Ϯ 15 266 Ϯ 19 280 Ϯ 19 295 Ϯ 22 305 Ϯ 25 pH 7.43 Ϯ 0.03 7.44 Ϯ 0.03 7.44 Ϯ 0.02 7.45 Ϯ 0.03 Ϯ Ϯ Ϯ Ϯ PCO2 (mm Hg) 35.1 5.4 31.8 4.0 29.0 5.3 29.5 4.8 Ϯ Ϯ Ϯ Ϯ PO2 (mm Hg) 76.3 7.5 84.5 5.4 89.2 11.7 89.0 8.2 BT (°C) 38.3 Ϯ 0.3 38.1 Ϯ 0.4 38.1 Ϯ 0.5 38.2 Ϯ 0.6 Control group IOP (mm Hg) 17.5 Ϯ 7.2 16.9 Ϯ 5.9 16.5 Ϯ 5.4 14.9 Ϯ 4.4 13.3 Ϯ 5.5 12.4 Ϯ 5.7 HR (beats/min) 277 Ϯ 30 276 Ϯ 27 274 Ϯ 26 277 Ϯ 29 273 Ϯ 27 283 Ϯ 22 pH 7.42 Ϯ 0.02 7.43 Ϯ 0.05 7.42 Ϯ 0.03 7.42 Ϯ 0.05 Ϯ Ϯ Ϯ Ϯ PCO2 (mm Hg) 34.6 2.9 32.8 2.8 32.3 4.3 32.8 4.1 Ϯ Ϯ Ϯ Ϯ PO2 (mm Hg) 73.5 8.5 84.5 6.3 87.8 9.1 88.4 9.6 BT (°C) 38.3 Ϯ 0.6 38.0 Ϯ 0.6 38.0 Ϯ 0.6 38.1 Ϯ 0.8

Data are mean Ϯ SD (n ϭ 10 and 11, respectively). HR, heart rate; BT, body temperature.

Downloaded from iovs.arvojournals.org on 09/29/2021 4870 Tamaki et al. IOVS, November 2003, Vol. 44, No. 11

TABLE 7. Systemic Parameters in Human Study

Pre 90 Min 180 Min 360 Min 540 Min

Lomerizine Mean BP (mm Hg) 81.0 Ϯ 4.9 79.1 Ϯ 7.4 77.6 Ϯ 5.7 81.9 Ϯ 7.7 82.3 Ϯ 4.4 Heart rate (beats/min) 70.0 Ϯ 7.5 69.0 Ϯ 10.6 64.0 Ϯ 8.1 71.0 Ϯ 5.0 65.0 Ϯ 7.9 IOP (mm Hg) 9.4 Ϯ 2.6 10.9 Ϯ 2.0 10.1 Ϯ 3.0 11.9 Ϯ 0.6 11.0 Ϯ 1.7 Placebo Mean BP (mm Hg) 82.3 Ϯ 4.5 79.1 Ϯ 3.9 77.0 Ϯ 5.5 81.4 Ϯ 10.8 80.8 Ϯ 4.8 Heart rate (beats/min) 70.0 Ϯ 5.2 66.0 Ϯ 4.8 65.0 Ϯ 6.0 72.0 Ϯ 6.9 65.0 Ϯ 6.9 IOP (mm Hg) 10.9 Ϯ 2.3 11.1 Ϯ 1.6 11.8 Ϯ 4.0 10.9 Ϯ 1.9 13.1 Ϯ 2.2

Data are the mean Ϯ SD of results in eight healthy volunteers. Mean BP, mean arterial blood pressure ϭ diastolic BP ϩ 1/3(systolic BP Ϫ diastolic BP).

The dose of lomerizine used in the present rabbit experi- same pharmacological effects in rabbit and humans. Maximum

ment was the one that affected the ONH circulation with little concentration (Cmax) after oral 5 mg lomerizine is 4.2 ng/mL in effect on systemic blood pressure in conscious rabbits. Plasma humans, and this dose signiﬁcantly affected the ONH circula- concentration 5 and 180 minutes after intravenous administration without any effect on systemic blood pressure in the tion of 0.3 mg/kg lomerizine in rabbits are 130 and 5 ng/mL, present subjects.36 Although the plasma concentration of respectively.18 Because of species difference, the same plasma lomerizine in the present rabbits may be some 10 times higher concentration of a calcium antagonist does not always elicit the than that in the present human subjects, as far as the effect on the ONH blood ﬂow and systemic blood pressure are con- cerned, pharmacological effects of lomerizine in the present human subjects are thought not to be much different from

those in the present rabbit experiment. In contrast, NBfovea showed no signiﬁcant change after oral lomerizine. The retinal capillaries are absent in the foveola, 0.4- to 0.5-mm diameter

capillary-free zone. In the present study, NBfovea was obtained from the ﬁeld of 0.32 ϫ 0.32 mm across a foveal area. Thus,

NBfovea should reflect not retinal, but choroidal blood flow. The slight effect of lomerizine on the choroidal blood flow is consistent with the result of the microsphere experiment in rabbits, by which choroidal blood flow was little affected by intravenous lomerizine. In the present human study, we could not investigate the effect of oral lomerizine on the retinal circulation because making laser speckle measurements using argon blue is difficult in human subjects. Further studies using scanning laser Doppler flowmetry are needed to investigate the effect of lomerizine on human retinal tissue circulation.37,38 In general, systemic administration of Ca2ϩ channel blockers may be complicated by side effects such as hypotension, palpitations, reflex tachycardia, peripheral edema, and vertigo. These adverse effects derive from the main action of Ca2ϩ channel blockers, a blockade of Ca2ϩ channels in peripheral arteries. It is desirable to use a Ca2ϩ channel blocker with few systemic effects in clinical practice in ophthalmology. Actually, there is evidence that the effect of lomerizine on blood pressure is weaker than those of other Ca2ϩ channel blockers (e.g., nicardipine, verapamil, and diltiazem) because lomerizine selectively inhibits KCl-induced Ca2ϩ influx through Ca2ϩ channels more potently in cerebral arteries than in mesenteric arteries.39 In fact, in anesthetized dogs it significantly increases vertebral blood flow with little effect on blood flow in peripheral arteries such as the mesenteric and femoral arteries.15 Clinical studies have also revealed lomerizine to have little effect on blood pressure or heart rate.17 Our finding that lomerizine increased blood flow in retinal and ONH tissues without changing choroidal blood flow suggests that its effect is more prominent on vessels in neural tissues, including those in the ocular circulation. A beneficial effect of oral calcium antagonists on glaucomatous visual-field FIGURE 3. Time course of changes in NB (A) and NB (B) after ONH fovea damage in a subset of patients with open-angle glaucoma, oral administration of lomerizine (F) or placebo (E) in humans. NB ONH including patients with NTG, has been suggested by several and NBfovea indicate the NB value expressed as a percentage of the 6–9,40,41 baseline measurement. Mean Ϯ SD in eight subjects in each plot. The investigators. This, together with its reported neuro-

intergroup difference was signiﬁcant for NBONH (ANOVA for repeated protective effect against ischemia–reperfusion damage in the measurements: treatment, P ϭ 0.031; treatment ϫ time, P ϭ 0.026). rat retina,34 suggests that lomerizine may have clinical poten-

Downloaded from iovs.arvojournals.org on 09/29/2021 IOVS, November 2003, Vol. 44, No. 11 Lomerizine and Ocular Circulation 4871

tial for conditions complicated by ocular circulatory distur- 21. Tamaki Y, Araie M, Kawamoto E, Eguchi S, Fujii H. Non-contact, bances in the retina or ONH. Effects of oral lomerizine in aged two-dimensional measurement of tissue circulation in choroid and subjects or patients with NTG deserve further study. optic nerve head using laser speckle phenomenon. Exp Eye Res. 1995;60:373–384. References 22. Tamaki Y, Araie M, Tomita K, Nagahara M, Tomidokoro A, Fujii H. Real-time measurement of human optic nerve head and choroid 1. Fechtner R, Weinreb RN. Mechanism of optic nerve damage in circulation using laser speckle phenomenon. Jpn J Ophthalmol. primary open angle glaucoma. Surv Ophthalmol. 1994;39:23–42. 1997;41:49–54. 2. Flammer J. The vascular concept of glaucoma. Surv Ophthalmol. 23. Nagahara M, Tamaki Y, Araie M, Fujii H. Real-time measurements 1994;38(suppl):S3–S6. of blood velocity in human retinal veins using the laser speckle 3. Cohn JN. Calcium, vascular smooth muscle, and calcium entry phenomenon. Jpn J Ophthalmol. 1999;43:186–195. blockers in hypertension. Ann Int Med. 1983;98:806–809. 24. Hale SL, Alker K, Kloner RA. Evaluation of nonradioactive, colored 4. Hof RP. Calcium antagonist and the peripheral circulation: differ- microspheres for measurement of regional myocardial blood flow ences and similarities between PY 108-068, nicardipine, verapamil in dogs. Circulation. 1988;78:428–434. and diltiazem. Br J Pharmacol. 1983;78:375–394. 25. Fercher AF, Briers JD. Flow visualization by means of single expo- 5. Ohtsuka M, Yokota M, Kodama I, Yamada K, Shibata S. New sure speckle photography. Opt Commun. 1981;37:326–330. generation dihydropyridine calcium entry blockers: in search of 26. Sugiyama T, Utsumi T, Azuma I, Fujii H. Measurement of optic greater selectivity for one tissue subtype. Gen Pharmacol. 1989; nerve head circulation: comparison of laser speckle and hydrogen 20:539–556. clearance methods. Jpn J Ophthalmol. 1996;40:339–343. 6. Kitazawa Y, Shirai H, Go FJ. The effect of Ca2ϩ-antagonist on visual 27. Tomita K, Araie M, Tamaki Y, Nagahara M, Sugiyama T. Effects of field in low-tension glaucoma. Graefes Arch Clin Exp Ophthalmol. nilvadipine, a calcium antagonist, on rabbit ocular circulation and 1989;227:408–412. optic nerve head in NTG subjects. Invest Ophthalmol Vis Sci. 7. Netland PA, Chaturvedi N, Dreyer EB. Calcium channel blockers in 1999;40:1144–1151. the management of low-tension and open-angle glaucoma. Am J Ophthalmol. 1993;115:608–613. 28. Kozuma C, Macklin W, Cummins LM, Mauer R. Anatomy, physiol- 8. Gaspar AZ, Flammer J, Hendrickson P. Influence of nifedipine on ogy, and biochemistry of the rabbit. In: Weisbroth SH, Flatt RE, the visual fields of patients with optic-nerve-head diseases. Eur J Kraus AL, eds. The Biology of the Laboratory Rabbit. New York: Ophthalmol. 1994;4:24–28. Academic Press; 1974:50–72. 9. Bose S, Piltz JR, Breton ME. Nimodipine, a centrally active calcium 29. Sasaki Y, Araie M, Takase M, Shirasawa H, Ishii Y. Effects of topical antagonist, exerts a beneficial effect on contrast sensitivity in befunolol, a beta-adrenergic blocking agent, on blood flow in patients with normal-tension glaucoma. Ophthalmology. 1995; rabbit eye. Jpn J Ophthalmol. 1981;25:299–305. 102:1236–1241. 30. Stjernschantz J, Bill A. Effect of intracranial stimulation of the 10. Sawada A, Kitazawa Y, Yamamoto T, Okabe I, Ichien K. Prevention oculomotor nerve on ocular blood flow in the monkey, cat, and of visual field defect progression with brovincamine in eyes with rabbit. Invest Ophthalmol Vis Sci. 1979;18:99–103. normal-tension glaucoma. Ophthalmology. 1996;103:283–288. 31. Waki M, Sugiyama T, Watanabe N, Ogawa T, Shirahase H, Azuma 11. Koseki N, Araie M, Yamagami J, Shirato S, Yamamoto S. Effects of I. Effect of topically applied iganidipine dihydrochloride, a novel oral brovincamine on visual field damage in normal tension glau- calcium antagonist, on optic nerve head circulation in rabbits. Jpn coma with low-normal pressure. J Glaucoma. 1999;8:117–123. J Ophthalmol. 2001;45:76–83. 12. Hara H, Morita T, Sukamoto T, Cutrer FM. Lomerizine (KB-2796), 32. Takahashi Y. Optic nerve head circulation in alloxan-induced dia- a new antimigraine drug. CNS Drug Rev. 1995;1:204–226. betic rabbits [in Japanese]. Nippon Ganka Gakkai Zasshi. 1995; 13. Kanazawa T, Toda N. Inhibition by KB-2796, a new Caϩϩ entry 99:166–172. blocker, of the contractile response of isolated dog cerebral arter- 33. Hatta S. Effects of intraocular pressure on the optic nerve head in ies. Folia Pharmacol Jpn. 1987;89:365–375. albino rabbits [in Japanese]. Nippon Ganka Gakkai Zasshi. 1993; 14. Kanazawa T, Nakasu Y, Masuda M, Handa J. Acute effect of 97:181–189. 1-[bis(4-fluorophenyl)methyl]-4-(2,3,4-trimethoxybenzyl)-pipera- 34. Toriu N, Akaike A, Yasuyoshi H, et al. Lomerizine, a Ca2ϩ channel zine dihydrochloride, KB-2796, on the cerebral blood flow in blocker, reduces glutamate-induced neurotoxicity and ischemia/ unanesthetized cats. Arch Jpn Chir. 1986;55:682–688. reperfusion damage in rat retina. Exp Eye Res. 2000;70:475–484. 15. Yamada C, Harada K, Shimamoto A, Sugimoto H, Nishimura N, 35. Tamaki Y, Araie M, Tomita K, Tomidokoro T. Time change of Sukamoto T. Effects of lomerizine on cerebral blood flow and nicardipine effect on choroidal circulation in rabbit eyes. Curr Eye systemic arterial blood pressure in anesthetized beagle dogs. Jpn Res. 1996;15:543–548. Pharmacol Ther. 1997;25:797–802. 36. Sakai T, Kawashima T, Satomi O, Awata N. Pharmacokinetics of 16. Nakashima M, Kanamaru M. Clinical phase 1 study of KB-2796 [in lomerizine in healthy male volunteers. Jpn Pharmacol Ther. 1994; Japanese]. Rinsho Iyaku. 1989;5:1791–1811. 22:4657–4662. 17. Gotoh F, Fukuuchi Y, Tashiro K, et al. Long-term trial of lomerizine 37. Michelson G, Schmauss B, Langhans MJ, Harazny J, Groh MJ. hydrochloride for migraine. Jpn Pharmacol Ther. 1995;23:1445– Principle, validity, and reliability of scanning laser Doppler flow- 1460. metry. J Glaucoma. 1996;5:99–105. 18. Shimazawa M, Sugiyama T, Azuma I, et al. Effect of lomerizine, a new Ca2ϩ channel blocker, on the microcirculation in the optic 38. Tamaki Y, Araie M, Fukaya Y, Ishii K. Validation of scanning laser nerve head in conscious rabbits: a study using a laser speckle Doppler flowmetry for retinal blood flow measurements in animal technique. Exp Eye Res. 1999;69:185–193. models. Curr Eye Res. 2002;24:332–340. 19. Toriu N, Sasaoka M, Shimazawa M, Sugiyama T, Hara H. Effect of 39. Iwamoto T, Morita T, Sukamoto T. Calcium antagonism by KB- lomerizine, a novel Ca2ϩ channel blocker, on the normal and 2796, a new diphenylpiperazine analogue, in dog vascular smooth endothelin-1-disturbed circulation in the optic nerve head of rab- muscle. J Pharm Pharmacol. 1991;43:535–539. bits. J Ocul Pharmacol Ther. 2001;17:131–149. 40. Flammer J, Guthauser U, Mahler F. Do vasospasms help cause low 20. Tamaki Y, Araie M, Kawamoto E, Eguchi S, Fujii H. Noncontact, tension glaucoma? Doc Ophthalmol Proc Series. 1987;49:397– two-dimensional measurement of retinal microcirculation using 399. laser speckle phenomenon. Invest Ophthalmol Vis Sci. 1994;35: 41. Gasser P, Flammer J. Influence of vasospasm on visual function. 3825–3834. Doc Ophthalmol. 1987;66:3–18.

Downloaded from iovs.arvojournals.org on 09/29/2021