Excitotoxic basolateral amygdala lesions potentiate the memory impairment effect of muscimol injected into the medial septal area.

In rats, the septo-hippocampal system is important for memory encoding. Previous reports indicate that muscimol, a specific GABAergic agonist induces learning and memory deficits when infused into the medial septal area. The basolateral nucleus of the amygdala (BLA) modulates memory encoding in other brain areas, including the hippocampus. To explore the interactions between the septo-hippocampal system and amygdala in memory, we studied the effects of intra-medial septal infusions of muscimol in rats with BLA lesions. Animals received sham surgery or excitotoxic BLA lesions and were given infusions of either vehicle or muscimol (5 nmol) into the medial septal area 5 min prior to training sessions in inhibitory avoidance and water maze tasks. In the inhibitory avoidance task, muscimol-induced memory impairment was potentiated by BLA amygdala lesions. Additionally, in the water maze task, BLA-lesioned rats given muscimol infusions into the medial septal also showed memory impairment. These findings indicate that the MSA interacts with the BLA in the processing of memory storage.