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

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. When the training session was fixed at 2 h once daily, shock-shock (S-S) interval at 5 s and response-shock (R-S) interval variable-20, 30 and 60 s, the acquisition speed of the response was almost constant 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 s, respectively, and the length of 1 session was varying-1, 2 and 4 h, the behavioral baseline was established after about 6 sessions independently of the length of the session. The cumulative time for the acquistion was shortest when 1 session was 1 h long, and longest when it was 4 h 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, 1 session of 1 h/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.