INFLUENCE OF VARIOUS NEUROLEPTIC DRUGS ON SHOCK AVOIDANCE RESPONDING IN RATS .2. NONDISCRIMINATED SIDMAN AVOIDANCE PROCEDURE WITH ALTERNATE REINFORCEMENT AND EXTINCTION PERIODS AND ANALYSIS OF INTERRESPONSE TIMES (IRTS)

The effects of seven neuroleptic drugs on conditioned behaviour were studied in rats by means of a lever-press shock-avoidance procedure (shock-shock 20 sec; response-shock 20 sec) with alternate reinforcement and extinction periods. All seven drugs inhibited the lever-press response and the shock-avoidance rate; their order of potency was trifluperidol > droperidol > haloperidol > pimozide > fluanisone > chlorpromazine > pipamperone. For all seven drugs, the response rate during the extinction periods was a more sensitive indicator of drug effect than the response rate during the reinforcement periods. Analysis of the temporal distribution of the IRT's shows that IRT's of 0-5″ and of 6-15″ were more sensitive to drug effects than IRT's of 16-20″ and of > 20″. The introduction of extinction periods together with the analysis of IRT's rendered the Sidman avoidance procedure the most sensitive test available for the quantitative evaluation of the potency of neuroleptic drugs in rats. The qualitative differences between the neuroleptics studied were less pronounced. There is some indication, however, that specific neuroleptics (e.g. pimozide) inhibit the response rate to about the same extent during both reinforcement and extinction periods, while aspecific neuroleptics (e.g. pipamperone) are more active inhibitors of the responses during extinction than during the corresponding reinforcement periods. © 1969 Springer-Verlag.