The loop neural circuit between the medial prefrontal cortex and the amygdala in the rat brain.

A major neuronal basis underlying emotion regulation is the inhibitory influence of the medial prefrontal cortex (mPFC) on amygdalar neurons. However, in spite of the importance of mPFC neuronal activities in emotion regulation, little is known about the inputs modulating activity of mPFC neurons projecting to the amygdala. To gain insight into dense reciprocal connections between mPFC and amygdala, we investigated neural circuits between these brain regions using electrophysiological techniques. We found that mPFC neurons were antidromically driven mainly by stimulation of the central nucleus of the amygdala (CeA), rather than the posterior part of the basolateral nucleus of the amygdala (pBLA), whereas pBLA, but not CeA, stimulation evoked orthodromic excitatory and inhibitory responses. mPFC neurons antidromically driven by CeA stimulation showed excitatory or inhibitory responses to pBLA stimulation. These findings indicate the existence of a functional neural loop between amygdala and mPFC, pointing to an amygdalar self-control system.