Endogenous hyperprolactinaemia and avoidance behaviors of the rat.

The influence of endogenous hyperprolactinaemia induced by pituitary homografts under the kidney capsule on conditioned avoidance behaviors of the rat has been investigated. Acquisition of active avoidance behavior, as studied in shuttle-box and pole jumping test situations, appeared to be facilitated in homografted rats in comparison with sham-operated animals. Extinction behavior was not affected in the same tests. Retention of one-trial learning passive avoidance behavior in homografted rats was similar to that of sham-operated animals. Hyperprolactinaemia resulted in a diminished behavioral responsiveness to electrical footshock. It is concluded that endogenous hyperprolactinaemia selectively affects acquisition, but not retention performance of avoidance behaviors.