Vasoactive intestinal peptide in the amygdala inhibits tail flick reflexes in rats

The present study was conducted to test the capability of a representative type of non-opioid peptides vasoactive intestinal peptide (VIP) in the amygdala to modulate nociception. Bilateral application of VIP into the basolateral region of the amygdala persistently suppressed radiant heat-evoked tail flick reflexes of anesthetized rats. The present result suggests that VIP synapses in the amygdala may play important roles in controlling pain, as with opioid synapses in the amygdala. This result also implies that local VIP in the amygdala is likely to subserve activating the descending antinociceptive systems of the brainstem from the amygdala.