Facilitating Effect of Oxiracetam and Piracetam on Acquisition of Discrete Two-Way Shuttle Avoidance in Normal Mice
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Facilitating Effect of Oxiracetam and Piracetam on Acquisition of Discrete Two-Way Shuttle Avoidance in Normal Mice Hisashi KURIBARA and Sakutaro TADOKORO Division for Behavior Analysis, Behavior Research Institute, Gunma University School of Medicine, 3-39-22 Showa-machi, Maebashi 371, Japan Accepted September 24, 1988 Abstract-Effects of oxiracetam and piracetam on acquisition of the discrete two way shuttle avoidance response were investigated in normal mice of the dd strain. When oxiracetam or piracetam was administered only once immediately before the training session, the mice showed a greater number of avoidance responses in comparison with the saline-treated control mice, with the maximum effect at 30 mg/ kg of oxiracetam and 100 mg/kg of piracetam. These results suggest that oxi racetam and piracetam facilitate the avoidance acquisition in normal mice. Piracetam, a cyclic GABA derivative, is facilitating acquisition of the discrete two thought to activate brain integrative mecha way shuttle avoidance in mice. nisms without eliciting behavioral excitation The experimental animals were male mice (1). Piracetam was followed by many an of the dd strain (Institute of Experimental alogus compounds such as aniracetam (2) Animal Research, Gunma University School and oxiracetam (3). It has been reported that of Medicine). We (10) have shown that this these compounds enhance learning and/or mouse strain rapidly acquires a discrete two memory in brain-damaged animals (1-5), in way shuttle avoidance and that the acquisi aged animals (6), and even in normal animals tion process is reliable and reproducible. (7, 8) in one-way active avoidance, passive When these mice were 8 weeks of age and avoidance and/or maze situations. Recently, weighed 28-32 g, the training of discrete Sansone et al. (9) studied effects of piracetam two-way shuttle avoidance was started. and oxiracetam on the acquisition of discrete Oxiracetam and piracetam were dissolved two-way shuttle avoidance in two strains in physiological saline immediately before (BALB/c and C57BL/6) of inbred mice. They use. The doses tested were 10, 30 and 100 reported a marked facilitation of the avoidance mg/kg, i.p., for both of the drugs, and each acquisition in BALB/c mice when the training injection volume was always constant at 0.1 / (5-daily sessions of 100 trials each) was 10 g body weight. preceded by the 5-day pretreatment regimen Five equivalent shuttle boxes (GT-8450, either piracetam (100 mg/kg, i.p.) or oxi O'Hara & Co., Ltd.) were used as described racetam (50 mg/kg, i.p.), but not by a 5-day previously (10-12). Briefly, the shuttle box treatment regimen with the same drug doses was 30(W)x9(D)x15(H) cm, to which 2 when they were injected 30 min before the infrared photo-beams, arranged 18 cm apart, start of each training session. Therefore, were attached. A speaker for presenting a Sansone et al. suggested that a pretreatment warning stimulus was located in the center for several days was a minimum requirement ceiling of the box. Solid state equipment (De to observe the facilitating-effect of piracetam CARES GT-M5; O'Hara & Co., Ltd.) simul and oxiracetam on the acquisition of discrete taneously controlled and recorded the be two-way shuttle avoidance in normal mice. haviors of each of 5 mice. The shuttle boxes The purpose of this experiment was to were placed in sound-attenuating chambers. study whether single administration of oxi The temporal parameters of the discrete racetam and piracetam was effective for avoidance schedule (13) consisted of an intertrial interval of 22 sec and a warning testing, and 2 groups of 20 animals received duration of 5 sec. The warning stimulus was saline as the control. The experiment was con an 800 Hz tone. An electric shock of 150 V, ducted between 9 a.m.-3 p.m. 0.5 mA, 50 Hz AC was given to the mouse The avoidance acquisition progressively through a stainless steel floor grid of the succeded in each training session. Therefore, shuttle box. The maximum duration of the numbers of the avoidance responses were shock presentation was 3 sec, but an escape calculated every 20 avoidance trials to observe contingency was inserted in the schedule. the acquisition process according to our pre Thus, an avoidance response was recorded vious study (12). when the mouse avoided the shock by run At first, the overall data were analyzed by a ning in the box and cutting the photo-beam repeated measures analysis of variance at the opposite side within 5 sec after the (ANOVA). If there were significant overall onset of the warning stimulus. Each training effects, comparisons between the individual session consisted of 1-hr training per day, mean values were conducted by the two tail during which 120 avoidance trials were car Student's t-test. When P values were equal to ried out at intervals of 30 sec. In this experi or less than 0.05, they were considered to be ment, 2 training sessions were held at a 24 hr significantly different. interval. Drugs or physiological saline (control One mouse in the saline-treated control injection) were administered only once im group was accidentally killed by passage of mediately before the start of the 1st session. electric current through the brain when it bit Twenty animals were used in each drug the floor grid. Since the saline-treated groups Fig. 1. Effects of oxiracetam (10, 30 and 100 mg/kg, i.p.) on acquisition of the discrete two-way shuttle avoidance in mice. The drug or physiological saline (control injection) was administered only once immediately before the start of the 1st training session. The 2nd training session was held 24 hr after the 1 st session without any additional treatment. Each training session lasted for 1 hr, during which 120 avoidance trials were carried out at intervals of 30 sec. Each point indicates the mean avoidance responses during every 20 avoidance trials. "indicates a significant difference from the saline-treated control value (P<0.05). demonstrated similar results, these data were mice after injection of these drugs. combined. Thus, the number of control mice The present experiment demonstrated that was 39. the acute administration of either oxiracetem Figures 1 and 2 show the effects of oxi or piracetam facilitated acquisition of a racetam and piracetam, respectively, on the discrete two-way shuttle avoidance in normal acquisition of the discrete two-way shuttle mice of the dd strain. Our results are com avoidance in the mouse. In these figures, the parable with those reported by Sansone et al. mean numbers of the avoidance responses (9) that 5-daily, but not acute, pretreatment during the block of every 20 avoidance trials with oxiracetem (50 mg/kg) or piracetam are presented. Since the number of shuttles (100 mg/kg) was effective for facilitating the were 21-28/block, and there was no signifi acquisition of two-way shuttle avoidance in cant difference between the saline-treated and mice in spite of differences in the experimental drug-treated groups, these data were not conditions from ours that included mouse presented in the figure. The analysis of strain, shuttle box, warning signal, drug ad variance of the overall avoidance responses ministration regimen. revealed that there were significant drug In the shuttle avoidance situation, an in effects and trial-by-treatment interactions. crease in general activity results in a facili The results of individual comparisons are tation of the avoidance behavior (10, 14). presented in each figure. Briefly, both oxi However, such a non-specific factor is racetam and piracetam facilitated the avoid unlikely to explain the present results, since ance acquisition not only in the 1st session gross observation failed to detect any evi but also in the 2nd session. The maximum dence of a drug-induced behavioral excita effects were observed at 30 mg/kg of oxirace tion. In addition, the drug doses tested in this tam and 100 mg/kg of piracetam. experiment elicited a marked change in neither A gross observation revealed that neither the established discrete two-way shuttle sedation nor excitation was detectable in the avoidance response nor the ambulatory Fig. 2. Effects of piracetam (10, 30 and 100 mg/kg, i.p.) on acquisition of the discrete two-way shuttle avoidance in mice. The data are shown in the same way as in Fig. 1. Int. Pharmacodyn. Ther. 275, 86-92 (1985) (locomotor) activity (H. Kuribara, unpub Ed. Sci. 39, 16-22 (1984) lished data). Furthermore, at higher doses, 4 Banfi, S., Dorigotti, L., Abbracchio, M.P. and these drugs tended to suppress the avoidance Balduini, W.: Methylazaxymethanol micro response and ambulatory activity, and they encephaly in rats: Neurochemical characteri reduced the ambulation-increasing effect of zation and behavioral studies with the nootropic methamphetamine. oxiracetam. Pharmacol. Res. Commun. 16, 67 83 (1984) The improvement of learning and memory 5 Banfi, S. and Dorigotti, L.: Experimental be by piracetam has been ascribed to its effects havioral studies with oxiracetam on different on interhemispheric communication, integra types of chronic cerebral impairment. Clin. tive mechanisms and memory retrieval pro Neuropharmacol. 7, Supp. 1, 768-769 (1984) cess (1, 15). Although piracetam and oxi 6 Mondadori, C. and Classen, W.: Effects of racetam are cyclic GABA derivatives, these oxiracetam on the performance of aged rats in drugs hardly affect GABAergic function, but a one-way active avoidance situation. Clin. rather activate cholinergic function in the Neuropharmacol. 7, Supp. 1, 770-771 (1984) brain (16, 17). In addition, we (12) have 7 Heise, G.A.: Behavioral methods for measuring demonstrated that amiridin, an acetylcholines effects of drugs on learning and memory in terase inhibitor, is effective for facilitating the animals.