Differential effects of unilateral lidocaine infusion into the globus pallidus on consolidation and performance of inhibitory avoidance.

The striatum is involved in memory consolidation; also involved in this process is one of its two major efferent targets, namely, the substantia nigra. It is not clear, however, if the other target, the globus pallidus, participates in storage and/or performance of learned information. To examine this problem, male Wistar rats were trained in an inhibitory avoidance task and tested for retention 24 h afterward. Independent groups were infused, unilaterally, with 2% lidocaine in the pallidus either 2 min after training or 2 min before testing. No disturbances of memory were detected with posttraining infusion, but a significant deficit in retention was observed as a consequence of pretest infusion. Infusion of isotonic saline into the globus pallidus, or of lidocaine before testing into the parietal cortex, after training into the ventral thalamic nucleus, and both before training and testing into this thalamic nucleus were without effect. Taken together, the data indicate that unilateral inactivation of the GP interferes with retrieval of information derived from inhibitory avoidance training, but not with the early stages of memory consolidation of this task, and other work indicates that the pallidus may be involved in a late phase of this process.