Lateral Orbitofrontal Cortical Modulation on the Medial Prefrontal Cortex-Amygdala Pathway: Differential Regulation of Intra-Amygdala GABAA and GABAB Receptors

ILA (Infralimbic area) UBERON:8440033 functionally connects to BLN (basolateral amygdaloid nuclear complex) UBERON:0006107 · Rat

Bipolar electrical stimulation of the medial prefrontal cortex (electrode in infralimbic cortex, possible spread to prelimbic) reliably evoked single spikes in putative projection neurons of the lateral and basolateral amygdala in anesthetized rats; 11 responsive neurons were found in Exp 1 and 9 in Exp 2. Only units with onset latencies under 30 ms, little latency shift with increasing intensity and low jitter were kept, which the authors take as monosynaptic and not antidromic; stimulus current was titrated so that baseline evoked spike probability was about 0.5 of 50 trials (49.3 ± 3.6% before and 50.3 ± 7.6% after drug application in 6 neurons).

Methods (electrically evoked responses); Results Exp 1 and 2; Fig. 2A, Fig. 3A

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AI (Agranular insular area) UBERON:0034893 functionally connects to BLN (basolateral amygdaloid nuclear complex) UBERON:0006107 · Rat

A conditioning electrical pulse in the lateral orbitofrontal cortex reduced the probability that mPFC stimulation evoked a spike in lateral/basolateral amygdala neurons, with significant suppression at lOFC-mPFC delays of 25-500 ms and no effect at 1000 ms. Nine of 11 neurons in Exp 1 and all 9 in Exp 2 were suppressed by the lOFC prepulse. Local iontophoresis of the GABA-A antagonist bicuculline abolished the suppression at both 25 and 100 ms delays, whereas the GABA-B antagonist saclofen reversed it only at the 100 ms delay, indicating the gating is mediated by intra-amygdala GABA receptors. Three of the 9 gated neurons in Exp 1 also received direct convergent input from the lOFC.

Results Exp 1 (Fig. 2B) and Exp 2 (Fig. 3B, Fig. 4)

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