Electrophysiological study of the response of medial prefrontal cortex neurons to stimulation of the basolateral nucleus of the amygdala in the rat.

The neural connections from the basolateral nucleus of the amygdala (BLA) to the medial prefrontal cortex (MPC) in urethane-anesthetized rats were investigated. Extracellular recordings were made from 200 neurons with spontaneous firing in the MPC, and the BLA was electrically stimulated. The most frequent response to BLA stimulation was inhibition (63.5%). Excitatory responses were found in 17 units (8.5%), while 56 neurons (28%) did not change their spontaneous firing after BLA stimulation. Inhibitory responses showed a wide range of latencies, suggesting the coexistence of mono- and polysynaptic pathways. On the contrary, the excitatory responses seem to be mediated by a monosynaptic pathway. BLA projections to the MPC play a predominantly inhibitory role in the spontaneous activity of prefrontal neurons. This inhibition may modulate central motor systems and motivated behaviors.