Cooperative interaction between the basolateral amygdala and ventral tegmental area modulates the consolidation of inhibitory avoidance memory

Abstract

The aim of the current study was to examine the existence of a cooperative interaction between the basolateral nucleus of amygdala (BLA) and the ventral tegmental area (VTA) in inhibitory avoidance task. The BLA and the VTA regions of adult male Wistar rats were simultaneously cannulated and memory consolidation was measured in a step-through type inhibitory avoidance apparatus. Post-training microinjection of muscimol, a potent GABA-A receptor agonist (0.01-0.02 μg/rat), into the VTA impaired memory in a dose-dependent manner. Post-training intra-BLA microinjection of NMDA (0.02-0.04 μg/rat), 5 min before the intra-VTA injection of muscimol (0.02 μg/rat), attenuated muscimol-induced memory impairment. Microinjection of a NMDA receptor antagonist, D-AP5 (0.02-0.06 μg/rat) into the BLA inhibited NMDA effect on the memory impairment induced by intra-VTA microinjection of muscimol. On the other hand, post-training intra-BLA microinjection of muscimol (0.02-0.04 μg/rat) dose-dependently decreased step-through latency, indicating an impairing effect on memory. This impairing effect was however significantly attenuated by intra-VTA microinjection of NMDA (0.01-0.03 μg/rat). Intra-VTA microinjection of D-AP5 (0.02-0.08 μg/rat), 5 min prior to NMDA injection, inhibited NMDA response on the impairing effect induced by intra-BLA microinjection of muscimol. It should be considered that post-training microinjection of the same doses of NMDA or D-AP5 into the BLA or the VTA alone had no effect on memory consolidation. The data suggest that the relationship between the BLA and the VTA in mediating memory consolidation in inhibitory avoidance learning may be dependent on a cooperative interaction between the glutamatergic and GABAergic systems via NMDA and GABA-A receptors.