Aversive conditioning of homozygous and heterozygous D.I. Brattleboro rats in the light-dark box.

Active and passive avoidance, and conditioned freezing acquisition and retention were studied in HODI and HEDI Brattleboro rats. All animals were from the same source and of the same age and sex. The light-dark box test was employed. 0.6 and 2.0 mA footshocks were administered for the same number (7) of daily trials. Extinction time-course was followed for seven consecutive daily trials. Passive avoidance: the conditioned response was acquired and retained equally well by all Ss and for both shock intensities. Active avoidance: for 0.6 mA shocks HODI Ss acquired and retained the response significantly better than HEDI Ss; for 2.0 mA shocks the response was acquired equally by both groups of Ss, and retained significantly better by HODI Ss. Freezing: in general, HODI Ss exhibited less freezing then HEDI Ss. The diverse conditioned behavior of HODI and HEDI Ss in this paradigm, which allows the contemporaneous investigation of several aversive responses, does not support the hypothesis that vasopressin deficiency impairs learning and memory in the rat.