Effects of Central Depressants on Rota-Rod and Traction Performances in Mice

Abstract

Abstract-Effectsof central depressants-chlorpromazine, diazepam, pentobarbital and ethanol-on rota-rod and traction performances in mice were investigated. The walking technique of the animals on the rotating rod (3 cm in diameter, 24 r. p. m.) was established after about 15 trials, and was well maintained for one week thereafter. No training was required for the traction.Both the rota-rod and traction performances were inhibited by chlorpromazine, diazepam, pentobarbital and ethanol in fairly good parallel with the dosages. However, the sensitivities to one same drug markedly differed between the two performances.Chlorpromazine more than diazepam inhibited the rota-rod, while in the traction performance the inhibition with diazepam was greater than that with chlorpromazine.Pentobarbital and ethanol inhibited the two perfor mances to nearly the same degree. On the basis of the present results, the rota-rod test is considered to be suitable for the estimation of the positive adaptability to forced motor activity, and the traction for that of muscle relaxation.By comparing the dose effect relationships in the two performances, it may be possible to elucidate the character istics of various central depressants, and to apply these procedures for the screening test in drug evaluations.When a mouse is repeatedly placed on a rod or cylinder which is rotating at a constant speed, the animal gradually learns to walk on it, adapting itself to the rotation speed. After ingestion of a central depressant, however, the animal easily falls from the rod. This procedure is called 'rota-rod test' and was first introduced by Dunham and Miya (1) for assaying the drug effects on the motor activity. Since then, the effects of various central depressants, investigated by this test have been reported (2-4). There is, however, no established interpretation of the results obtained by this test, for many factors, e.g. lowered general activity, ataxia, muscle relaxation, fatigue, etc, are considered to inhibit the rota-rod performance (RR performance).On the other hand, when a mouse hangs from a thin bar by means of its forelimbs, the animal can maintain this posture for a certain time without falling. This traction behavior (TR performance) or grasping reflex is also sharply altered by central depressants.We studied the effects of various central depressants on these two performances, and found that the sensitivities differed depending on the drug. MATERIALS AND METHODSAdult, male ddG strain mice were obtained from the breeding room of Gunma Univer sity, Medical School. A solid diet MF (Oriental Yeast Co., Tokyo) and tap water were

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