AUTORADIOGRAPHIC LOCALIZATION OF CALCITONIN-GENE-RELATED PEPTIDE RECEPTORS IN GUINEA-PIG RESPIRATORY-TRACT - EFFECT OF CAPSAICIN PRETREATMENT

Calcitonin gene-related peptide (CGRP) is a potent vasodilator peptide present in capsaicin-sensitive neurons innervating the respiratory tr act. In this study, the autoradiographic distribution of [I-125]CGRP b inding sites was investigated in guinea pig airways. Extremely dense s pecific binding occurred over parenchymal tissue, with moderate specif ic binding over tracheal glands, the endothelium of pulmonary veins an d arteries, and small blood vessels in the bronchial wall. The localiz ation of binding sites for [I-125]CGRP over blood vessels but not bron chial smooth muscle correlates well with the physiological actions of this peptide, although the function of the parenchymal sites is unknow n. No significant difference in binding was seen in vehicle- or capsai cin-pretreated animals, suggesting that sites are not reliant on facto rs from capsaicin-sensitive neurons.