Muscimol injected into the right or left amygdaloid complex differentially affects retention performance following aversively motivated training.

The effects of intra-amygdala infusion of the GABAA agonist, muscimol, prior to retention testing was examined. In Expt. 1, rats were trained in a one-trial inhibitory-avoidance task and given bilateral intra-amygdala infusions of vehicle or muscimol or simultaneous unilateral infusions of each, 5 min before the retention test 24 h after training. Expt. 2 used the same procedures as those in Expt. 1 but two retention measures were taken: initial step-through latency and the number of trials to reach criterion during continuous multiple-trial inhibitory-avoidance (CMIA) training. Groups given bilateral infusions of muscimol or unilateral infusion of muscimol into the right amygdala had significantly shorter latencies to enter the dark compartment than groups given bilateral infusions of vehicle or unilateral infusion of muscimol into the left amygdala. Bilateral muscimol infusions impaired acquisition of CMIA relative to bilateral vehicle infusions or unilateral muscimol infusion into the left amygdala. These results suggest differential involvement of the right and left amygdala in memory.