Mechanism of vasodilation by cochlear nerve stimulation. Role of calcitonin gene-related peptide

Rabbit aortic rings pre-contracted with 1 mu M phenylephrine were exposed t o organ fluid of isolated guinea pig cochleas which had been subjected to e lectrical field stimulation (FS, 50 Hz, 50 V, 0.2 ms over 2 min). This resu lted in an endothelium-dependent relaxation of the vessel rings sensitive t o glibenclamide, an ATP-sensitive K+ channel blocker. Tetrodotoxin (1 mu M) added to the cochlear fluid blocked the vasorelaxant effect of cochlear FS and it attenuated vasorelaxation when added to aortic rings. The relaxatio n response paralleled an increase in the level of calcitonin gene-related p eptide (CGRP) in both cochlear and vascular organ fluids from undetectable pre-stimulation values to 0.12 +/- 0.029 and 0.44 +/- 0.051 nM, respectivel y. We conclude that CORP possibly contributes to cochlear nerve stimulation -induced endothelium-dependent vasorelaxation. (C) 1999 The Italian Pharmac ological Society.