THE EFFECTS OF CALCITONIN GENE-RELATED PEPTIDE (CGRP) ON COCHLEAR AND MUCOSAL BLOOD-FLOW IN THE ALBINO RABBIT

The effects of intravenously infused calcitonin gene-related peptide (CGRP) on the regional blood flow of the cochlea, the middle ear and the upper respiratory tract were studied. Two series of experiments were performed without pretreatment on either conscious or pentobarbital anaesthetized animals; in one series the cervical sympathetic chain was severed on one side; in another series anaesthetized animals were subjected to ganglionic blockade with hexamethonium bromide in order to abolish reflexes involving the autonomic nervous system. In still another series conscious animals were pretreated with indomethacin in order to reduce the formation of prostaglandins. In all groups of animals where sympathetic influence was diminished cochlear blood flow increased during the infusion of CGRP. In the mucosa of middle ear and the upper airways, the blood flow increased in all groups. The results indicate that CGRP at these doses causes vasorelaxation in the mucosa of the middle ear and upper airways and does so also in the cochlea if the sympathetic influence is abolished.