Medial amygdala enhances synaptic transmission and synaptic plasticity in the dentate gyrus of rats in vivo.

Abstract

1. The present experiment was designed to test whether synaptic transmission and synaptic plasticity in the dentate gyrus were modulated by the medial amygdala (MeA). Field potentials in the dentate gyrus (DG) evoked by stimulations of the medial perforant path (PP) were extracellularly recorded in anesthetized rats. 2. Although single-pulse stimulation of the MeA augmented PP stimulation-evoked population spike amplitude in the DG transiently, high-frequency stimulation (100 Hz for 1 s) of the MeA induced long-lasting enhancement of synaptic transmission that was not occluded by PP tetanus-induced long-term potentiation (LTP). 3. When high-frequency stimulation of the MeA was applied concurrently with weak tetanus of the PP, which alone induced only marginal LTP, the magnitude of LTP increased considerably. 4. These results demonstrate that neuron activities in the MeA induce short- and long-lasting changes in the excitability of the PP-DG synapses and thereby enhance their synaptic plasticity.