Effects of intraseptal infusion of muscimol on inhibitory avoidance and spatial learning: Differential effects of pretraining and posttraining administration

Abstract

Previous research in our laboratory showed that the pretraining administration of the GABAergic agonist muscimol into the medial septal area (MSA) of rats impaired place learning in a water-maze task. To determine whether this treatment impaired memory by acting at the time of training or after training, the first experiment examined the effects of posttraining intraseptal infusion of muscimol on retention in the place-learning task. The posttraining muscimol treatment facilitated learning on the second day of training (1 and 5 nmol) and produced an impairment on only one of the three retention measures on the free-swim trial (5 nmol). In additional experiments using an inhibitory avoidance task, pretraining, but not posttraining, administration of muscimol (5 nmol) into the MSA impaired retention. The findings of these experiments suggest that intraseptal administration of muscimol impairs memory formation primarily by affecting processes occurring at the time of training.