Guinea pig vestibular blood flow in response to calcitonin-gene related peptide

Little is known about the physiologic regulation of the vestibular end organ blood flow. The purpose of the current study was to examine posterior semicircular canal ampulla blood flow in addition to systemic factors during intravenous infusions of calcitonin-gene related peptide (CGRP), a factor involved in the tonic regulation of blood flow. Receptors for this factor are known to be available to the vascular supply of the vestibular organs. Local blood flow using laser Doppler flowmetry and systemic parameters were monitored during infusion of CGRP, CGRP antagonists and control vehicle. The results show relatively stable vestibular blood flow (VBF), concentration-dependent decreases in systemic blood pressure, and elevations in heart rate. Pretreatment with CGRP(8-37), a specific receptor antagonist, attenuated these responses to subsequent CGRP infusions. These findings suggest a rigid regulation of VBF in the presence of a systemically active vasodilator.