Cutaneous Mechanical Stimulation Regulates Ovarian Blood Flow Via Activation of Spinal and Supraspinal Reﬂex Pathways in Anesthetized Rats

Japanese Journal of Physiology, 55, 265–277, 2005

Cutaneous Mechanical Stimulation Regulates Ovarian Blood Flow via Activation of Spinal and Supraspinal Reﬂex Pathways in Anesthetized Rats

Sae UCHIDA, Fusako KAGITANI, Harumi HOTTA, Tomoko HANADA*, and Yoshihiro AIKAWA*

Department of the Autonomic Nervous System, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo, 173-0015 Japan; and *Graduate School of Humanities and Sciences, Ochanomizu University, Bunkyo-ku, Tokyo, 112-0012, Japan

Abstract: The reflex effects of noxious mechanical to a monophasic increase due to an increase in stimulation of a hindpaw or abdominal skin MAP. After spinal transection, stimulation of the on ovarian blood flow, and the reflex pathways left abdomen produced a moderate increase involved in those responses were examined in in MAP, a remarkable increase in ovarian sym- anesthetized rats. Blood flow in the left ovary was pathetic nerve activity and a slight decrease in measured using a laser Doppler flowmeter, and ovarian blood flow during the stimulation. In con- the activity of the left ovarian sympathetic nerve trast, stimulation of the right abdomen produced and mean arterial pressure (MAP) of the common a smaller response in ovarian sympathetic nerve carotid artery were recorded. Stimulation of the activity during the stimulation while it increased left or right hindpaw for 30 s produced marked the MAP to a similar degree. Ovarian blood flow increases in ovarian sympathetic nerve activity slightly increased after the end of stimulation, and MAP. Ovarian blood flow slightly decreased which was explained as passive vasodilation due during the stimulation and then slightly increased to the increase in MAP. In conclusion, stimulation after the stimulation. After the left ovarian sym- of somatic afferents affects ovarian blood flow by pathetic nerves were severed, the same stimulus inducing changes in ovarian sympathetic nerve produced a remarkable monophasic increase in activities and blood pressure. When stimulation ovarian blood flow that was explained by passive was applied to a hindpaw whose segment of af- vasodilation due to a marked increase in MAP. ferent input is far from the segment of the ovarian After spinal transection at the third thoracic (T3) sympathetic nerves, it took a supraspinal reflex level, the responses of MAP, ovarian sympathetic pathway. However, when stimulation was applied nerve activity, and ovarian blood flow to hind- to the abdomen whose spinal segment of the af- paw stimulation were nearly abolished. Stimula- ferent is close to the segment of the ovarian sym- tion of the abdomen at the right or left side for pathetic nerve output, there are spinal segmental 30 s produced slight increases in ovarian sym- reflex pathways. The present results demonstrate pathetic nerve activity and MAP. Ovarian blood that spinal reflexes depend on the laterality of the flow slightly decreased during the stimulation and stimulus, while supraspinal reflexes do not de- then slightly increased after the stimulation. After pend on the laterality of the stimulus. [The Japa- the ovarian sympathetic nerves were severed, nese Journal of Physiology 55: 265–277, 2005] the response of the ovarian blood flow changed

Key words: autonomic nervous system, ovarian blood ﬂow, ovarian sympathetic nerve, cutaneous stimulation, rat.

Received on Sep 30, 2005; accepted on Oct 31, 2005; released online on Nov 1, 2005; DOI: 10.2170/jjphysiol.R2133 Correspondence should be addressed to: Sae Uchida, Department of the Autonomic Nervous System, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015 Japan. Phone: +81-3-3964-3241 (Ext. 3086), Fax: +81-3-3579-4776, E-mail: [email protected]

Japanese Journal of Physiology Vol. 55, No. 5, 2005 265 S. UCHIDA et al.

MATERIALS AND METHODS The ovary is innervated by autonomic nerves in addition to being under the control of hormones (see Thirty-seven virgin female Wistar rats, 4–10 months review by Burden [1]). Histological studies in rats old (body weight, 170–240 g), were used for the showed that the autonomic nerves innervating the present experiments. The estrous cycle of each animal ovary are sympathetic nerves and vagus nerves [2–5]. was determined by monitoring vaginal smears; 5 of Recently, we demonstrated in anesthetized rats that the 37 rats were in proestrus, 18 were in estrus, 2 were stimulation of the sympathetic nerve that innervates the in metestrus, and 12 were in diestrus on the day of the ovary causes a reduction in ovarian blood flow, while experiment. Rats were kept in a room with a 12 h:12 h stimulation of the vagus efferent nerve that innervates light–dark schedule, with rat chow and water provided the ovary had no effect on ovarian blood flow [6]. ad libitum. This study was approved by the Animal Furthermore, we demonstrated that application of a Committee of our institution. noxious mechanical stimulus to a hindpaw produced a Surgical procedures. Animals were reduction in ovarian blood flow during the stimulation anesthetized with urethane (1.1 g/kg, I.P.). The by activating the ovarian sympathetic vasoconstrictor trachea was cannulated and respiration was artificially nerve [6]. maintained using a respirator (Model 683, Harvard,

Somatic afferent stimulation produces conscious Holliston, Massachusetts, USA). The end-tidal CO2 sensation, emotional responses, and various autonom- concentration, which was monitored by a gas monitor ic responses. These somatically-induced autonomic (1H26, NEC San-ei, Tokyo, Japan), was kept at 3–4% responses including blood flow changes are produced by controlling the respiratory volume and frequency. by activation of an autonomic efferent nerve. Some of The systemic blood pressure was continuously these autonomic responses induced by somatic stimu- recorded through a cannula in a common carotid artery lation are reflex responses called somato-autonomic with a strain gauge (TP-400T, Nihon Kohden, Tokyo, reflexes. The central reflex pathways of somato-sym- Japan). A jugular vein was cannulated for infusion pathetic reflexes consist of segmental spinal reflexes of necessary solutions. The animal was immobilized and generalized supraspinal reflexes (see reviews, [7– by administration of gallamine triethiodide (20 9]). Supraspinal reflexes seem to be activated particu- mg/kg, I.V., Sigma, St. Louis, MO). The core body larly when a limb afferent is stimulated, and segmental temperature, which was monitored in the rectum, was reflexes seem to be activated by stimulation of spinal maintained at around 37.5°C using a body temperature segmental afferents entering the spinal cord at the control system containing a thermostatically-regulated level of thoracic and higher lumbar segments. In rats, DC current heating pad and infrared lamp (ATB-1100, the sympathetic nerve innervating the ovary emerges Nihon Kohden, Tokyo, Japan). During the experiments, from the spinal cord mainly at the segments of T9 and urethane (10% of the dose used for initial anesthesia) T10 [3], while afferent inputs of the hindpaw enter the was administered I.V. every 1–2 h. spinal cord at the level of L3–L5 [10]. This anatomi-

cal evidence suggests that the sympathetically-medi- ovarian laser Doppler A B aorta plexus n. flowmeter ated reduction in ovarian blood ﬂow during hindpaw rec. right left stimulation takes supraspinal reﬂex pathways instead

of segmental reflex pathways. ovarian The present study was performed to clarify whether artery ovary cover there are spinal and/or supraspinal reflex components uterine glass abdomen artery in the response of ovarian blood flow to cutaneous uterus stimulation. For this purpose, we applied noxious stimulation to a hindpaw whose afferent enters the spinal cord at the level of L3–L5, and also to the abdominal skin whose afferent enters the spinal cord at hindpaw 10 mm around the level of T9–T12 [11]. To examine the pres- Fig. 1. Schematic diagram of the experimental proce- ence of spinal reflex pathways, we prepared spinalized dures. A: Pinching was applied to the left or right hindpaw rats whose spinal cord was transected at the level of or the abdominal area (hatched area) at the left or right side T3. Furthermore, we examined the involvement of so- for 30 s. B: Blood flow in the left ovary was measured using a laser Doppler flowmeter. Efferent nerve discharges were matic afferent nerves and ovarian sympathetic efferent recorded from the left ovarian sympathetic nerve (ovarian nerves in the somatically-induced ovarian blood flow plexus nerve). Ovarian blood flow and ovarian sympathetic changes. nerve activity were recorded in different animals.

266 Japanese Journal of Physiology Vol. 55, No. 5, 2005

Fig. 1 Central Reflex Pathways of Somato-Ovarian Vascular Reflexes Measurement of ovarian blood flow. Blood monitored on an oscilloscope to guard against count- flow in the left ovary was measured in 21 rats using ing any artifacts of recordings that might arise. a laser Doppler flowmeter (ALF21D, Advance, To- In our previous study, we found that the response kyo, Japan) (Fig. 1B). After ventral exposure of the of ovarian sympathetic nerve activity to pinching of left ovary with a wide abdominal wall opening, the a hindpaw in central nervous system (CNS)–intact ovary itself was gently placed on a small plate. The rats was not influenced by cutting the bilateral vagus probe (outer diameter, 1.0 mm) of the flowmeter was nerves [6]. Therefore, in most of the experiments in gently placed in contact with a cover glass (about 7 × the present study, the vagus parasympathetic nerves 7 mm) that had been placed on a surface of the ovary were kept intact. that was devoid of any visible large vessels. Care was Severance of somatic afferent nerves. In 5 taken to avoid compressing the ovary. The probe of the rats, somatic afferent nerves innervating a hindpaw flowmeter was fixed in place using a balancing holder and abdomen were severed. The spinal nerves between (ALF-B, Advance, Tokyo, Japan). the T8 and T13 levels were separated from the sur- Spinal transection. Full transection of the spi- rounding tissues and cut along the spine. The femoral nal cord was performed at the third thoracic (T3) level and sciatic nerves were cut in the femoral area. in 10 anesthetized rats. The systolic blood pressure Data analysis. The ovarian blood flow, mean ar- was kept above 70 mmHg by injection of 4% Ficoll terial blood pressure (MAP) and ovarian sympathetic 70 (Amersham Biosciences, Uppsala, Sweden) after nerve activity were calculated in 10-s intervals and spinal transection. expressed as percentages of the prestimulus values. Cutaneous stimulation. Cutaneous nocicep- Values were expressed as means ± SEM. Statistical tive stimulation was applied by pinching an area of analysis was performed by analysis of variance (ANO- approximately 1 cm2 of the skin of the left or right VA) followed by Dunnett’s multiple comparison test. hindpaw or the skin of the abdominal area on the left Statistical significance was set at p < 0.05. or right side for 30 s (Fig. 1A). The force of pinching was approximately 3 kg [12]. RESULTS Severance of sympathetic nerves innervating the ovary. The ovarian sympathetic nerves were Effect of hindpaw pinching in CNS-intact rats denervated in 7 rats. Denervation of the left ovarian Response of ovarian blood flow and MAP sympathetic nerves was performed by cutting the sus- to hindpaw pinching. Among 11 CNS-intact ani- pensory ligament and accompanying blood vessels to mals, the ovarian blood flow and MAP under the rest- cut the left superior ovarian nerve, and by applying ing condition before applying any cutaneous stimula- a local anesthetic, procaine (1.0%), on a small piece tion were 377.3 ± 29.6 mV and 105.6 ± 4.9 mmHg, of cotton to the left ovarian artery approximately 10 respectively. mm proximal to the ovary to block the ovarian plexus Pinching either the left or right hindpaw for 30 s nerve ipsilateral to the ovary that was used for blood always produced an increase in MAP and a decrease in flow recording. ovarian blood flow during the stimulation as shown in Recording of efferent nerve activity from a representative recording in Fig. 2A. Figure 3, A and the ovarian plexus nerve fibers innervating D, shows the results in 17 cases. Pinching of a hind- the ovary. In 16 rats, efferent nerve discharges of the paw reduced ovarian blood flow to 95.3 ± 1.2% of the left ovarian plexus nerve were recorded (Fig. 1B). The control level during the stimulation, and the ovarian ovarian plexus nerve running along the ovarian artery blood flow then increased to approximately 106% of was cut at about 10 mm from the ovary and covered the control level at 20 to 30 s after the end of stimula- with warm liquid paraffin. The efferent discharge ac- tion. During the stimulation, the MAP increased to a tivity from the proximal part of the cut end was led maximal blood pressure of 128.1 ± 2.8% of the control through a bipolar platinum-iridium wire electrode value and it remained elevated for more than 90 s after and amplified using a preamplifier (S-0476, Nihon the end of stimulation. These responses were elicited Kohden) with a 0.01 s time constant. Nerve discharg- upon stimulation of either the left or right hindpaw. es were counted in 5-s intervals using a computer Therefore, the data obtained by stimulation of the left (ATAC-3700, Nihon Kohden), and the rate of nerve or right hindpaw were combined in Fig. 3, A and D. discharges was recorded on a polygraph (RM-6000, Severance of somatic afferent nerves. When Nihon Kohden). Discharge activity was continuously the sciatic and femoral nerves on the same side in

Japanese Journal of Physiology Vol. 55, No. 5, 2005 267 S. UCHIDA et al. CNS-intact ovarian symp. n. intact ovarian symp. n. severed Fig. 2. Typical responses of ovarian blood ﬂow, mV 310 B mV MAP and ovarian sym- A 700 blood blood pathetic nerve activity 260 flow flow 650 to pinching of a hind- mmHg paw in CNS-intact rats. 140 120 A, B: Responses of ovar- MAP 120 MAP ian blood ﬂow and MAP 100 mmHg in the ovarian sympathet- hindpaw, pinching, 30 s ic nerve-intact (A) and severed (B) conditions. C: Responses of ovarian C sympathetic nerve activ- imp/5s ity and MAP. Five-second ovarian 360 symp. n. delay in nerve recording activity 280 due to counting princi- 110 ple was corrected. The MAP 90 bottom bar indicates the mmHg time of stimulation.

ovarian symp. n. intact ovarian symp. n. severed * * * * hindpaw, pinching * * * * % * 130 * * * CNS-intact * * * 120 % A ∗ ∗ 110 B 110 blood 100 100 brain flow ∗ 90 * 140 C spinal cord * * % * * 130 * * * * * * * * * * * * * 120 T * * * ovarian C blood vessel 110 ovarian symp. n. 100 symp. n. activity * Fig. 2 * * * L * * * * * 130 * * 130 * * * % * % * * * * 120 * * 120 right S left * * * * * * * * * * * * * * * * hindpaw hindpaw D * * 110 E * * 110

MAP 100 100 -30 0 30 60 90 120 s -30 0 30 60 90 120 s hindpaw, pinching hindpaw, pinching Fig. 3. Summary of the responses of ovarian blood flow, ages of the prestimulus values (ordinates). The thin dashed MAP and ovarian sympathetic nerve activity to pinch- vertical lines and the thick horizontal bars on the abscissa ing of the left or right hindpaw in CNS-intact rats. A, B, indicate the time of stimulation. Each point and vertical bar D, E: Responses of ovarian blood flow (A, B) and MAP (D, represent the mean ± SEM. The onset of pinching stimula- E) in ovarian sympathetic nerve-intact (A, D; n = 17 in 11 tion was set as time zero (abscissa). *p < 0.05, **p < 0.01, rats) and severed (B, E: n = 8 in 7 rats) conditions. C: Re- significantly different from the prestimulus control values sponse of ovarian sympathetic nerve activity (n = 17 in 12 using one-way repeated ANOVA followed by Dunnett’s mul- rats). Each animalFig.3 was tested 1–2 times. The ovarian blood tiple comparison test. The schema on the left illustrates the flow, MAP and ovarian sympathetic nerve activity were cal- experimental preparation. culated in 10-s intervals and were expressed as percent-

268 Japanese Journal of Physiology Vol. 55, No. 5, 2005 Central Reflex Pathways of Somato-Ovarian Vascular Reflexes which stimulation was unilaterally delivered were it remained elevated after the stimulus was removed. cut proximal to the stimulus, the responses of ovarian Figure 3C summarizes the number of impulses in blood flow and MAP to pinching of a hindpaw were 17 cases. The nerve activity during the stimulation abolished (n = 5). reached a maximal level of 138.5 ± 4.5%; although Severance of ovarian sympathetic nerve. it started to slightly decrease during the stimulation, After the left ovarian sympathetic nerves were severed, it remained elevated up through 90 s after the end of pinching of the left or right hindpaw was performed. stimulation. Ninety seconds after the end of stimula- Upon pinching a hindpaw, the MAP increased, similar tion, the nerve activity was still elevated at 114.8 ± to the response observed before the ovarian sympa- 3.7%. The elevated level of nerve activity gradually thetic nerves were severed , while the ovarian blood returned to the control level over the next 30–60 s. This flow showed a remarkable monophasic increase as response of the ovarian sympathetic nerve was elicited shown in a representative case (Fig. 2B) and in the by stimulation of either the left or right hindpaw. summarized results of 8 cases (Fig. 3, B and E). The MAP reached a maximal level during the 30-s pinch- Effect of hindpaw pinching in spinalized rats ing stimulation of 127.9 ± 4.3%. The ovarian blood Response of ovarian blood flow and MAP flow increased during the pinching stimulation and re- to hindpaw pinching. Among 4 spinalized ani- mained significantly elevated after the end of stimula- mals, the ovarian blood flow and MAP under the rest- tion for approximately 60 s, reaching a maximal level ing condition were 368.8 ± 88.6 mV and 71.6 ± 2.8 of 132.8 ± 4.8%. mmHg, respectively. Response of the activity of the ovarian sym- Stimulation of either the left or right hindpaw pro- pathetic nerve to hindpaw pinching. Among the duced a marginal increase in MAP, reaching a maxi- 12 CNS-intact rats examined, the spontaneous efferent mal level of approximately 102% (Figs. 4, A and B, mass activity of the ovarian sympathetic nerve before and 5, E and F). Stimulation of either hindpaw did not applying any cutaneous stimulation was 407.3 ± 42.1 significantly change the ovarian blood flow (Figs. 4, A impulses/5 s. and B, and 5, A and B). As shown in Fig. 2C, the level of nerve activity was Response of ovarian sympathetic nerve ac- elevated during the hindpaw pinching stimulation and tivity to hindpaw pinching. Among the 4 spinal-

spinalized

left stimulation right stimulation

mV mV A 300 B 480 blood flow 250 430 70 80 MAP 60 70 mmHg mmHg hindpaw, pinching, 30 s

C imp/5s D imp/5s ovarian 320 260 symp. n. activity 240 180 70 65 MAP 60 55 mmHg mmHg Fig. 4. Typical responses of ovarian blood ﬂow, MAP and ovarian sympathetic nerve activity to pinching of a hindpaw in spinalized rats. A, B: Responses of ovarian blood ﬂow and MAP. C, D: Responses of ovarian sympathetic nerve activity and MAP. A, C: stimulation of left hindpaw. B, D: stimulation of right hindpaw.

Japanese Journal of Physiology Vol. 55, No. 5, 2005 269

Fig. 4 S. UCHIDA et al.

hindpaw, pinching

spinalized left stimulation right stimulation

% % A 110 B 110 blood 100 100 flow 90 90

% % 110 110 cut T3 ovarian C D ovarian symp. n. blood vessel 100 100 activity

symp. n. % % 110 110 * * * * E * * F * * MAP 100 100 right left hindpaw hindpaw -30 0 30 60 90 120 s -30 0 30 60 90 120 s hindpaw, pinching hindpaw, pinching

Fig. 5. Summary of the responses of ovarian blood ﬂow (A, B), MAP (E, F) and ovarian sympathetic nerve activity (C, D) to pinching of a hindpaw in spinalized rats. A, C, E: stimulation of left hindpaw. B, D, F: stimulation of right hindpaw. n = 7 in 4 rats for blood ﬂow and MAP; n = 4 in 4 rats for ovarian sympathetic nerve activity. Other details are as in Fig. 3.

ized rats, the spontaneous efferent mass activity of the 108% of the control level. Overall, among the 17 cas- ovarian sympathetic nerve was 377.0 ± 61.9 impulses/ es, the MAP increased during the stimulation and re- 5s. Fig.5 mained elevated after the end of stimulation for 90 s, Pinching of the left hindpaw for 30 s produced a reaching a maximal level of 109.3 ± 1.7%. Abdominal marginal increase in MAP, as mentioned earlier (Fig. pinching of either the left or right side elicited these 4C). Efferent nerve activity of the ovarian sympathetic responses. The ovarian blood flow during abdominal nerve slightly increased (Fig. 4C), the difference not stimulation of the left or right side reached a minimum being statistically significant (Fig. 5C). Pinching of of 95.0 ± 1.0% and 94.6 ± 2.2%, respectively. the right hindpaw produced a marginal increase in Severance of somatic afferent nerves. When MAP similar to left hindpaw pinching, and it did not the spinal nerves were cut between the T8 and T13 lev- significantly change the level of nerve activity (Figs. els proximal to the stimulus on the same side in which 4D and 5D). stimulation was unilaterally delivered, the responses of ovarian blood flow and MAP to abdominal pinching Effect of abdominal pinching in CNS-intact were abolished (n = 5). rats Severance of ovarian sympathetic nerve. Response of ovarian blood flow and MAP to After the left ovarian sympathetic nerves were sev- abdominal pinching. Abdominal pinching for 30 s ered, pinching of the abdomen produced an increase on either the left or right side produced an increase in in MAP in most cases and a decrease in MAP in some MAP in most cases (11 out of 17 cases), although it cases during the stimulation, as observed before the sometimes produced a reduction in MAP (4 out of 17 ovarian sympathetic nerves were severed. Figure 6B, cases) or no response in MAP (2 out of 17 cases). Re- a and b, shows 2 typical examples during abdominal gardless of whether the MAP increased or decreased, pinching. In cases where the MAP increased during the ovarian blood flow decreased during the stimulation abdominal pinching, ovarian blood flow also increased as shown in Fig. 6Aab. Among the 17 cases (Fig. 7, A in parallel with the MAP (Fig. 6Ba). In cases where and D), pinching the abdominal skin reduced ovarian the MAP decreased during the abdominal pinching, blood flow during the stimulation to 94.9 ± 1.0% of ovarian blood flow decreased in parallel with MAP the control level, although the ovarian blood flow then (Fig. 6Bb). Overall, among the 15 cases (Fig. 7, B and started to recover during the stimulation and increased E), the MAP increased during pinching of the abdo- 20 to 50 s after the end of pinching, reaching about men and it remained elevated for 90 s after the end

270 Japanese Journal of Physiology Vol. 55, No. 5, 2005 Central Reﬂex Pathways of Somato-Ovarian Vascular Reﬂexes CNS-intact CCNNSS--iinnttaacctt ovarian symp. n. intact ovarian symp. n. severed oovvaarriiaann ssyymmpp.. nn.. iinnttaacctt oovvaarriiaann ssyymmpp.. nn.. sseevveerreedd

mVmV A a mVmV B a mV A a mV B a 373070 A a 454050 B a 370 blobolodod 450 blobolodod blofolodw blofolodw 320 flow 404000 flow 320 flow 400 flow 320 101000 100 101000 MAP 100 MAMPAP 8080 MAP MAP 80 MAP 8080 mmmHmgHg 80 mmHg mmmHmgHg abadbodmoemne, np,inpcinhcinhgin, g3,03s0 s mmHg abdomen, pinching, 30 s mVmV mV mV mV bb 434030 b mV470 430 b 470 blobolododb blobolododb 470 blood blood flofwlow 380 flofwlow flow 380 flow 424020 380 420 101000 101000 MAMPAP 100 MAMPAP 100 MAP 80 MAP 80 8080 m8m0Hg 80 mmHg mmmHmgHg mmHg mmHg Fig. 6. Typical responses of ovarian blood flow, MAP and ovarian sympathetic nerve activity to pinching of imp/5s C a imp/5s the abdomen in CNS-intact rats. A, B: Responses of ovar- C a i5m0p50/050s C a 500 ian blood flow and MAP in ovarian sympathetic nerve-intact ovoavriaarnian ovarian (A) and severed (B) conditions. C: Responses of ovarian symsypm. pn.. n. 424020 symp. n. acativcittiyvity 420 sympathetic nerve activity and MAP. a, b in A–C: Sample activity recordings of two different response patterns. 111010 MAMPAP 110 MAP 9090 90 mmmHmgHg and remained elevated after the end of stimulation for mmHg 90 s. The ovarian sympathetic nerve activity started to b imipm/5ps/5s increase during the stimulation, reaching a maximal b imp4/850s ovoavriaarnianb 480 level of 109.6 ± 2.1%, and an elevated level of nerve ovarian 480 symsypm. pn.. n. symp. n. activity was observed until 70 s after the end of stimu- acativcittiyvity 404000 activity 400 lation (Fig. 7C). These responses were elicited upon 101000 100 MAMPAP abdominal stimulation of either the left or right side. MAP 8080 80 mmmHmgHg mmHg Effect of abdominal pinching in spinalized rats Responses of ovarian blood flow and MAP of stimulation; the ovarian blood flow also increased to abdominal pinching. In the 5 spinalized rats, during the stimulation and remained elevated after the pinching of the left abdomen for 30 s always produced end of stimulation for 90 s, reaching a maximal level an increase in MAP and a decrease in ovarian blood of 116.2 ± 3.6%. flow (Fig. 8A; summarized data in Fig. 9, A and E). Response of ovarian sympathetic nerve During the stimulation, the MAP started to increase activity to abdominal pinching in CNS-intact significantly while ovarian blood flow decreased, rats. In CNS-intact rats, when the MAP increased reaching a minimal level of 94.9 ± 1.3%. After the end during pinching of the abdominal skin, ovarian sym- of stimulation, the MAP remained elevated for 60 s, pathetic nerve activity also increased (Fig. 6Ca). How- although the ovarian blood flow recovered to the origi- ever, when the MAP decreased during pinching of nal level. abdominal skin, the nerve activity slightly decreased Stimulation of the right abdomen produced an in- during the stimulation (Fig. 6Cb). Overall, among the crease in MAP as did stimulation of the left abdomen 17 cases, the MAP increased during the stimulation (Figs. 8B and 9F). However, stimulation of the right FFFiiggig.. .666 Japanese Journal of Physiology Vol. 55, No. 5, 2005 271 S. UCHIDA et al.

abdomen, pinching ovarian symp. n. intact ovarian symp. n. severed CNS-intact % * * * * * * * * * * * * * 120 * * * * * % * * * * * * * A * * * * 110 B * 110 blood 100 flow 100 * * * * 90

* * % * * * * * C * * * * * * * 110 ovarian ovarian right left blood vessel symp. n. abdomen 100 activity

symp. n.

* * * * % * * * % * * * * * * * * * * * * * * * * * * 110 * * * * * * * 110 D * * * E * * * * * * * MAP 100 100 -30 0 30 60 90 120 s -30 0 30 60 90 120 s abdomen, pinching abdomen, pinching

Fig. 7. Summary of the responses of ovarian blood ﬂow, (D, E) in ovarian sympathetic nerve-intact (A, D; n = 17 in MAP and ovarian sympathetic nerve activity to pinch- 13 rats) and severed (B, E; n = 15 in 6 rats) conditions. C: ing of the left or right abdomen in CNS-intact rats. A, Responses of ovarian sympathetic nerve activity (n = 17 in B, D, E: Responses of ovarian blood ﬂow (A, B) and MAP 10 rats). Other details are as in Fig. 3.

Fig. 7 spinalized

left stimulation right stimulation A mV B mV 270 270 blood flow 220 220 70 70

MAP 60 60 mmHg mmHg abdomen, pinching, 30 s

imp/5s C D imp/5s 440 360 ovarian symp. n. 360 activity 280 70 65 MAP 60 55 mmHg mmHg

Fig. 8. Typical responses of ovarian blood ﬂow, MAP and ovarian sympathetic nerve activity to pinching of the abdomen in spinalized rats. A, B: Responses of ovarian blood ﬂow and MAP. C, D: Responses of ovarian sympathetic nerve activity and MAP. A, C: left side stimulation. B, D: right side stimulation.

272 Japanese Journal of Physiology Vol. 55, No. 5, 2005

Fig. 8 Central Reﬂex Pathways of Somato-Ovarian Vascular Reﬂexes

abdomen, pinching spinalized left stimulation right stimulation

% * * % A 110 B * * * 110 blood 100 100 flow * * * * 90 90

* * * * * % * 130 * % * 120 * 120 cut T3 * * * ovarian * * right left blood vessel C 110 D 110 abdomen ovarian symp. n. 100 100 symp. n. activity

* % * * % * * * * * * * 110 * * * * * 110 E * * * * * * * * * * * * * * * * * F * * * MAP 100 100 -30 0 30 60 90 120 s -30 0 30 60 90 120 s abdomen, pinching abdomen, pinching

Fig. 9. Summary of the responses of ovarian blood ﬂow (A, B), MAP (E, F) and ovarian sympathetic nerve activity (C, D) to pinching of the abdomen in spinalized rats. A, C, E: left side stimulation. B, D, F: right side stimulation. n = 8 in 5 rats for blood ﬂow; MAP, n = 4 in 4 rats for ovarian sympathetic nerve activity. Other details are as in Fig. 3.

abdomen produced an increase in blood flow in the sponse of ovarian blood flow changed to a remarkable left ovary, reaching a maximal level of 107.8 ± 1.6% monophasic increase. This indicates that the remark- (Figs. 8B and 9B), in contrast to its response to left able increase in ovarian blood flow in the absence of abdominal stimulation. ovarian sympathetic nerves was due to a remarkable Response of ovarian sympathetic nerve increase in blood pressure, which would cause a pas- activity to abdominal pinching. Pinching of the sive increase in blood flow. These results confirm our abdominal skin on the left sideF ofig spinalized. 9 rats for previous findings [6]. 30 s produced an increase in nerve activity during The present study first examined whether the reflex the stimulation, reaching a maximal level of 129.5 ± centers for the responses of blood flow and ovarian 5.6%, as well as an increase in MAP (Figs. 8C and sympathetic nerve activity to hindpaw pinching are 9C). Pinching of the right abdominal skin for 30 s pro- located in the supraspinal structure in the brain or spi- duced a similar response in the MAP as that upon left nal cord using spinalized rats. After spinal transection abdominal stimulation, but interestingly the response at the T3 level, stimulation of the left or right hindpaw of the nerve activity, reaching only 109.5 ± 2.6%, was produced a slight increase in blood pressure. Howev- much less than that produced by stimulation of the left er, stimulation of either hindpaw did not significantly abdomen (Figs. 8D and 9D). change ovarian sympathetic nerve activity nor ovarian blood flow. These results indicate that in spinalized DISCUSSION rats hindpaw stimulation can produce a slight increase in blood pressure but there may not exist any spinal Ovarian vasoconstriction during hindpaw reflex pathways from the hindpaw afferent to the spi- pinching. In CNS-intact rats, noxious mechanical nal ovarian sympathetic nerve preganglionic neurons; stimulation of either the left or right hindpaw pro- accordingly, hindpaw stimulation would exert little duced a marked increase in ovarian sympathetic nerve influence on ovarian blood flow. The slight increase activity as well as blood pressure. Ovarian blood flow in blood pressure appears to be too weak to influence slightly decreased during the stimulation and then ovarian blood flow. slightly increased after the stimulation. After den- These results may indicate that in CNS-intact rats, ervation of the ovarian sympathetic nerves, the re- hindpaw afferents take a supraspinal reflex pathway to

Japanese Journal of Physiology Vol. 55, No. 5, 2005 273 CNS-intact spinalized S. UCHIDA et al. Fig. 10. Schematic diagrams of the reflex pathway to the CNS-intact spinalized A B ovarian blood vessel produced by pinching of a hindpaw brain (A, B) or the abdomen (C, D) in CNS-intact (A, C) and spi- brain stem nalized (B, D) rats. A: Pinching of a hindpaw results in con- A brain B striction of ovarian blood vessels through excitation of the brain stem C spinal cord ovarian sympathetic nerve via a supraspinal reflex pathway. B: After spinal transection, pinching of a hindpaw does not C spinal cord cause ovarian vasoconstriction. C: Pinching of the abdomen T cut T3 results in ovarian vasoconstriction through excitation of the T T9 cut T3 ovarian sympathetic nerve via a spinal and/or supraspinal symp. n. symp. n. T9 reflex pathway. Spinal reflex pathways are tonically inhib- symp. n. symp. n. ited by the brain through an inhibitory descending pathway T10 L (indicated by the broken line) from the brain. D: After spinal L3 T1o0varian blood vessel L transection, inhibitory descending pathways are eliminated L3 ovarian blood vessel and pinching of the abdomen results in ovarian vasocon- hindpaw L5 S hindpaw striction through excitation of the ovarian sympathetic nerve hindpaw hindpaw L5 S via the spinal reflex pathway. , excitatory effect; , inhibitory effect. E: In spinalized rats, pinching of the abdomen ipsilateral (left) to the recording side of ovarian sympathetic C D nerve activity elicits much stronger activation of the spinal C D reflex than pinching of the abdomen contralateral (right) to the recording side.

cut T3 right left cut T3 right left

T9T9 sysmymp.pn. .n. ssyymmpp..nn..

abdaobmdoemnen aabbddoommeenn T12T12

symsypm. np.. n.

connect to the ovarian sympathetic nerves (Fig. 10A). with severed ovarian sympathetic nerves. The increase The central reflex pathway in the spinal cord between in ovarian blood flow after the end of stimulation in hindpaw afferents and the ovarian sympathetic nerves rats with intact ovarian sympathetic nerves was aug- is very weak or none (Fig. 10B), as demonstrated mented after severance of the ovarian sympathetic in other sympathetic nerves by Araki et al. [13] and nerves. These results suggest that after the ovarian Kimura et al. [14]. sympathetic nerves were severed, the elevated blood Ovarian vasoconstriction during abdominal pressure probably produced passive vasodilation and pinching. When the central nervous system was kept consequently ovarian blood flow increased. When intact, stimulation of the abdomen on either the left the ovarian sympathetic nerve was intact, abdominal or right produced an increase in ovarian sympathetic pinching increased the activity of this nerve, which nerve activity as well as an increase in blood pressure seemed to produce vasoconstriction and consequently during and after the end of stimulation. However, the reduced ovarian blood flow during abdominal stimula- ovarian bloodFig flow. 1 0 decreased during the stimulation tion, in which there was a slight increase in blood pres- and increasedFig. after10 the end of stimulation. After the sure. However, after the end of stimulation, the blood ovarian sympathetic nerves were severed, stimulation pressure increased and a small increase in sympathetic of the abdomen produced a similar increase in blood nerve activity resulted in a marginal increase in ovari- pressure; however, the response of ovarian blood flow an blood flow. In some cases, abdominal pinching pro- changed to a monophasic increase. The initial decrease duced a decrease in blood pressure in CNS-intact rats, in blood flow during the stimulation that was seen in in agreement with the report of Kaufman et al. [15]. rats with intact ovarian sympathetic nerves changed When the MAP decreased during abdominal pinch- to an increase response during the stimulation in rats ing, the level of ovarian sympathetic nerve activity

274 Japanese Journal of Physiology Vol. 55, No. 5, 2005 Central Reflex Pathways of Somato-Ovarian Vascular Reflexes slightly decreased during the stimulation and ovarian at the spinal level, it was reported in other organs that blood flow decreased whether the ovarian sympathetic stimulation of a somatic afferent ipsilateral to the side nerves were intact or severed. The decrease in ovarian of the sympathetic nerve that was being recorded, blood flow during the depressor response to abdomi- caused much stronger activation of the reflex pathway nal pinching is suggested to be a passive response due than stimulation of the contralateral somatic afferent to the decrease in blood pressure. [14, 16]. After spinal transection at T3, stimulation of the left Central reflex pathways of somato-ovarian (ipsilateral) abdomen produced a moderate increase vascular reflexes. In conclusion, stimulation of so- in blood pressure, a remarkable increase in ovarian matic afferents has some influence on ovarian blood sympathetic nerve activity and a slight decrease in flow that is attributed to reflex responses in ovarian ovarian blood flow. The moderate increase in blood sympathetic nerve activity and blood pressure. The pressure seems to be weaker than the remarkable in- afferent pathway consists of the cutaneous afferent crease in ovarian sympathetic nerve activity; thus, the nerves innervating the area that is stimulated. The cen- sympathetic vasoconstrictive effect was competitively tral reflex pathways of the pressor responses elicited stronger than the passive vasodilative effect of the in- by noxious mechanical stimulation of various segmen- creased blood pressure on ovarian blood flow, result- tal skins have been reported [14]. The present study ing in a slight decrease in blood flow. showed that there are two types of reflex pathways, In the spinalized rats, however, stimulation of the supraspinal and propriospinal, in the somato-ovarian right (contralateral) abdomen produced a similar in- vascular reflexes; whether the supraspinal or proprios- crease in blood pressure as did stimulation of the left pinal pathway is activated depends on which cutane- abdomen, although it induced a much smaller increase ous segment is stimulated. The reflex pathway from in left ovarian sympathetic nerve activity; therefore, the hindpaw afferent, which enters the spinal cord at the ovarian blood flow showed only a slight increase the level of L3–L5 [10], to the ovarian sympathetic after the end of stimulation. In this case, the increase nerve which emerges from the spinal cord mainly at in blood pressure was competitively stronger than the T9–T10 [3], is a supraspinal pathway. There are at slight increase in ovarian sympathetic nerve activity, least five segments between this pair of afferent and resulting in a marginal increase in blood flow. efferent, which seem to be too far apart to take a spi- Considering these data, the central reflex pathways nal reflex pathway. When the spinal segments of so- for ovarian blood vessels produced by abdominal stim- matic afferent stimulation and the ovarian sympathetic ulation are shown in Fig. 10, C–E. In CNS-intact rats, nerve are close to each other, as tested in this study, abdominal stimulation takes spinal and/or supraspinal the central reflex pathway from an abdominal affer- reflex pathways (Fig. 10C). After spinal transection, ent entering the spinal cord at around T9–T12 [11] to strong spinal segmental reflex pathways from ab- the ovarian sympathetic nerve takes segmental spinal dominal afferents to ovarian sympathetic nerves ap- reflex pathways in spinalized animals; this was also pear (Fig. 10D). The strong spinal reflex pathways that noted by Sato and Schmidt [17] in a study on cats. The were observed in the spinalized rats, seem to be sup- abolishment of the response of ovarian blood flow to pressed by a supraspinal structure through a descend- hindpaw stimulation in spinalized rats was not due to ing inhibitory pathway from the brain, which is shown spinal shock, because in the same spinalized rats ab- as a broken line in Fig. 10C, and after spinal transec- dominal stimulation produced clear spinal reflexes. tion, this descending inhibitory effect was eliminated In the present study, the spinal reflexes elicited by and resulted in the appearance of clear responses at abdominal stimulation in spinalized rats depended the spinal segmental levels (Fig. 10D). Interestingly, on the laterality of stimulation, while the supraspinal when an abdominal stimulation has spinal segmental reflexes elicited by hindpaw stimulation in CNS-in- reflex pathways from an afferent to the ovarian sym- tact rats did not depend on the laterality of stimula- pathetic nerves, it was noted to have a different effect tion. The responses of ovarian blood flow and ovarian on left ovarian sympathetic nerve activity depending sympathetic nerve activity to abdominal stimulation on whether the left or right abdominal afferent was in CNS-intact rats did not show any laterality to pinch- stimulated. Stimulation of the left abdomen produced ing, suggesting activation of the supraspinal reflex a much stronger effect on left ovarian sympathetic pathway. However, it remains to be answered if there nerve activity than stimulation of the right abdomen are two reflex pathways of spinal segmental and su- (Fig. 10E). Regarding the somato-sympathetic reflex praspinal reflex pathways to the ovarian sympathetic

Japanese Journal of Physiology Vol. 55, No. 5, 2005 275 S. UCHIDA et al. nerves when abdominal skin stimulation is delivered pathways. Therefore, the changes in ovarian sympa- to CNS-intact rats. thetic nerve activity elicited by somatic afferent stim- The supraspinal reflex pathway from a somatic af- ulation probably have an effect on ovarian hormonal ferent to the ovarian sympathetic nerve which influ- production in addition to ovarian blood flow. ences ovarian blood flow is quite different from the In the present study, we demonstrated that activa- reflex pathways involved in somatically-induced tion of ovarian sympathetic nerve activity by noxious blood flow changes in the uterus. The reflex pathway stimulation to the skin at various segmental skins such of the somato-uterine vascular reflex was proven to as the hindpaw and abdomen, changes ovarian blood take a segmental spinal reflex pathway from a somatic flow. In these cases, the reflex pathways were proven afferent entering the sacral spinal cord to the sacral to take supraspinal pathways and therefore, we could parasympathetic uterine nerves, resulting in vasodila- prove that stimulation of different segmental skin ar- tion of the uterus [18]. It is interesting that although eas in anesthetized animals had similar vasoconstric- the ovary and uterus are female reproductive organs tive effects on ovarian blood flow. In conscious ani- that are in close proximity to each other, the somati- mals, somatic stimulation leads to conscious sensation cally activated vasomotor nerves influencing ovarian and also emotional responses that may add a further blood flow and uterine blood flow are quite different; level of complexity to somato-autonomic interaction. somatic stimulation activates the sympathetic vaso- It would be interesting to further study whether the constrictor nerve to the ovary [6] and the cholinergic activity of ovarian sympathetic nerves is influenced by vasodilator nerve to the uterus [19]. Somatic stimula- higher CNS structures that are involved in emotional tion also activates different central reflex pathways; it responses, and whether these descending influences activates the supraspinal reflex pathway in the case of from the higher nervous system to the ovarian sym- ovarian sympathetic nerves and the segmental spinal pathetic nerves interact with somatic afferent stimula- reflex pathway in the case of uterine parasympathetic tion. nerves. Significance of somato-ovarian sympathet- We are grateful to Prof. Akio Sato and Prof. Yuko Sato of the ic reflexes. The ovary has two distinct functions of University of Human Arts and Sciences for their encourage- ment to complete this study. This work was supported by ovulation and production of female hormones. Zack- a Grant-in-Aid for Scientific Research from the Ministry of risson et al. [20] reported that ligation of the ovarian Education, Science, Sports and Culture of Japan (to S.U.). artery in rats resulted in a decrease in ovarian blood flow, a decrease in the rate of ovulation induced by REFERENCES gonadotropin injection, and a decrease in serum progesterone concentration. Therefore, the activity of the 1. Burden HW: The adrenergic innervation of mammalian sympathetic vasoconstrictor nerve to the ovary seems ovaries. In: Serono Symposia Publications from Raven Press, vol. 18, Catecholamines as Hormone Regula- to have effects on ovulation and the production of pro- tors. eds. Ben-Jonathan N, Bahr JM, and Weiner RI, gesterone via changes in ovarian blood flow. Further- Raven Press, New York, pp 261–278, 1985 more, the passive change in ovarian blood flow due to 2. 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