A Parabrachial-to-Amygdala Circuit That Determines Hemispheric Lateralization of Somatosensory Processing.

BACKGROUND: The central amygdala (CeA) is a bilateral hub of pain and emotional processing with well-established functional lateralization. We reported that optogenetic manipulation of neural activity in the left and right CeA has opposing effects on bladder pain. METHODS: To determine the influence of calcitonin gene-related peptide (CGRP) signaling from the parabrachial nucleus on this diametrically opposed lateralization, we administered CGRP and evaluated the activity of CeA neurons in acute brain slices as well as the behavioral signs of bladder pain in the mouse. RESULTS: We found that CGRP increased firing in both the right and left CeA neurons. Furthermore, we found that CGRP administration in the right CeA increased behavioral signs of bladder pain and decreased bladder pain-like behavior when administered in the left CeA. CONCLUSIONS: These studies reveal a parabrachial-to-amygdala circuit driven by opposing actions of CGRP that determines hemispheric lateralization of visceral pain.