Analytical Study of Acquisition on Free-OperantAvoidance Response for Evaluation of Psychotropic Drugs in Rats*

Abstract

Abstract-Systematic research was performed on the acquisition of free-operant (Sidman-type) avoidance response, which is widely used for the study of psychotropic drugs, with the following results: When the training session was fixed at 2 hours once daily, shock-shock (S-S) interval at 5 seconds, and response-shock (R-S) interval variable-20, 30 and 60 seconds, the acquisition speed of the response was almost con stant independent of the R-S interval, about 6 sessions being always required. When the S-S and R-S intervals were constantly 5 and 30 seconds, respectively and the length of one session was varying-1, 2 and 4 hours, the behavioral baseline was established after about 6 sessions independently of the length of the session. Thus the cumulative time for the acquisition was shortest when one session was 1 hour long, and longest when it was 4 hours long. There was a linear relation with negative inclination between the logarithm of mean numbers of shock delivered per session and the number of sessions. In rapid and exact training of animals for the evaluation of drug effects, one session of an hour per day is adequate. In the evaluation of drug effects on the acquisition process, observation of the shift in logarithmic value of shocks delivered is recommended.The free-operant (Sidman-type) avoidance (1) is one form of operant behavior most extensively used for the evaluation of psychotropic drugs. As for the practical method of animal training, workers' views are varying, and there is yet no consensus (2-7).The authors want to propose an adequate method of animal training, and in addition to analyse the regularity between the acquisition progress and the number of shocks delivered, in order to emphasize the pharmacological applicability of this relation. MATERIALS AND METHODSSubjects: Wistar strain male rats, bred by brother-sister mating for more than 20 years in the Department of Pharmacology were used. They were fed a solid diet of MF (Oriental Co. Tokyo) and given tap water ad libitwn. At the start of training, the animals were age 70-100 days and weighed 250-300 g.Thirty-five rats were divided into 7 groups of 5 according to experimental conditions. Except for the period of experiment, the groups were separately maintained in their respective cages.* Supported by a special fund from The Science and Technology Agency of Japan for promoting multiministrial projects [1973][1974][1975] on "The studies on regeneration of nervous tissue"

Rat Strain Differences in the Acquisition of Conditioned Avoidance Responses and in the Effects of Diazepam

“…Previously the authors (19,20) reported that the temporal para meters such as R-S and S-S intervals in Sidman-type avoidance schedule, and ITI in the discriminated avoidance schedule had little influence on the learning speed. Hoffman et a!…”