ANTEROGRADE EFFECTS OF A SINGLE ELECTROCONVULSIVE SHOCK ON INHIBITORYAVOIDANCE AND ON CUED FEAR CONDITIONING

A single electroconvulsive shock (ECS) or a sham ECS was administered to male 3-4-month-old Wistar rats 1,2, and 4 h before training in an i nhibitory avoidance lest and in cued classical fear conditioning (meas ured by means of freezing lime in a new environment). ECS impaired inh ibitory avoidance at all times and, at 1 or 2 h before training, reduc ed freezing time before and after re-presentation of the ECS. These re sults are interpreted as a transient conditioned stimulus (CS)-induced anxiolytic or analgesic effect lasting about 2 h after a single treat ment, in addition to the known amnesic effect of the stimulus. This su ggests that the effect of anterograde learning impairment is demonstra ted unequivocally only when the analgesic/anxiolytic effect is over (a bout 4 h after ECS administration) and that this impairment of learnin g is selective, affecting inhibitory avoidance but not classical fear conditioning to a discrete stimulus.