Reciprocal interactions between the basolateral amygdala and infralimbic and prelimbic regions of the mPFC: Actions of diazepam.

The basolateral amygdala (BLA) and prelimbic (PL) and infralimbic (IL) cortices are interconnected structures that participate in the regulation of fear. Unknown are the reciprocal functional influence of these regions on neuronal responsivity and the action of an anxiolytic drug. We performed multiunit activity recordings from one neuronal pool while applying electrical stimulation to another neuronal pool. In the same experimental session, PL-BLA and IL-BLA sequences of stimulation-recording were applied, followed by the inverse sequence (BLA-PL and BLA-IL). Using this procedure, we obtained information from the same neuronal pool that was stimulated and recorded. Using peristimulus histograms, we analyzed neuronal responsivity. In the saline-treated group, the PL-BLA stimulation-recording sequence produced an inhibitory response. The inverse sequence, BLA-PL, produced an excitatory response. For BLA-IL and IL-BLA stimulation-recording sequences, a minimal response was observed in the saline control group. Diazepam minimally affected responsivity of the PL-BLA and BLA-IL connections. Diazepam blocked the initial excitatory response of the IL-BLA connection. Under control conditions, the PL and BLA appeared to regulate each other. Under the action of diazepam, the IL exerted an inhibitory influence on the BLA. Because of the well-known actions of this anxiolytic drug on the BLA, this combined action may result in the synergistic control of fear.