OPPOSITE EFFECTS ON 2 DIFFERENT MEASURES OF RETENTION FOLLOWING UNILATERAL INACTIVATION OF THE AMYGDALA

We previously reported finding differential effects of unilateral infu sion of lidocaine into the right and left amygdalae prior to a retenti on test 24 h after one-trial inhibitory avoidance training. The presen t study was undertaken to determine whether the degree of training in an escape task influences the effects of unilateral inactivation of th e amygdala with lidocaine prior to the retention test. Male Sprague-Da wley rats, implanted with bilateral cannulae aimed at the amygdaloid c omplex received 0 (no shock), 2, or 10 training trials in a footshock- motivated escape task (0.4 mA). Forty-eight h later, the rats received bilateral microinfusions into the amygdalae of either buffer, or lido caine into one amygdala and buffer in the other, 5 min before they wer e tested for retention of the escape training using a continuous multi ple trial inhibitory avoidance (CMIA) procedure (0.4 mA). Forty-eight h after CMIA training the animals were retested, this time without inf luence of drugs. As indicated by initial response latencies on the fir st retention test, unilateral inactivation of either the right or the left amygdala severely impaired retention performance for the escape t raining regardless of the number of prior escape training trials recei ved. However, unilateral inactivation of either amygdala had no effect on acquisition of CMIA. Furthermore, unilateral inactivation of eithe r amygdala during CMIA training did not affect retention tested 48 h l ater. These results suggest that the differential involvement of the r ight and left amygdalae may be limited to certain training conditions. Furthermore, these findings demonstrate opposite effects on 2 differe nt measures of retention indicating that the method of testing retenti on affects the interpretation of the memory impairment induced by infu sion of lidocaine into the amygdala. (C) 1997 Elsevier Science B.V.