Cochlear Microcirculation: Effect of Adrenergic Agonists on Arteriole Diameter

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Abstract
• We used intravital fluorescent microscopy coupled with computerized video image processing to examine the cochlear microvasculature. In Mongolian gerbils the bulla was opened ventrally and a small window was made in the second turn of the cochlea. After fluorescein isothiocyanate-dextran administration, the radiating arterioles were video-recorded under X675 magnification. Computer determinations of arteriolar response to norepinephrine bitartrate (mixed α1α2 agonist), phenylephrine hydrochloride (a, agonist), and UK 14304 tartrate (α2 agonist) were made at multiple dose levels over time. Findings were consistent with arteriolar constriction in response to α-adrenergic stimulation. The presence of a, and α2 receptors was established, and a predominance of α2 receptors in the cochlea was suggested. (Arch Otolaryngol Head Neck Surg. 1990;116:411-417)