Role of  1-Adrenoceptor Subtypes in Pupil Dilation Studied With Gene-Targeted Mice

Abstract

The α₁-AR-induced mydriasis in mice is mediated mainly by the α₁A-AR, with a smaller contribution of the α₁B-AR, matching the relative abundance of these subtypes at the mRNA level. The lack of a single α₁-AR subtype does not appear to cause atrophy in the mouse iris.

Role of α1-adrenoceptor subtypes on corneal epithelial thickness and cell proliferation in mice

“…Findings in other ocular structures suggested a predominant role of the ␣ 1A -AR subtype in mediating ophthalmic artery constriction in mice, while the ␣ 1B -AR subtype was demonstrated to mediate adrenergic responses of iridial and retinal arterioles in rats and mice, respectively (3,9,12). Moreover, the ␣ 1A -AR was predominantly involved in mediating adrenergic pupil dilation of various species, including humans, rabbits, rats, and mice (17,23,25,27,41). Studies in humans who had been on medication with ␣ 1 -AR antagonists, primarily the ␣ 1A -AR-selective antagonist tamsulosin, demonstrated peripheral iris or iris dilator muscle thinning, indicative of a disuse atrophy of the iris dilator muscle when the receptor was blocked (11,30,33).…”

Running from a Bear: How We Teach Vasopressors, Adrenoreceptors, and Shock

“…Pupils dilate to survey the landscape for other predators and identify potential escape routes. Mydriasis is mediated primarily via α-1 receptors ( 2 ). In addition, and perhaps more clinically relevant to critical care, α-1 facilitates the diversion and optimization of blood flow for the sympathetic response, shunting blood away from the viscera, skin, and splanchnic system so that it is available to the muscles ( 3 – 5 ).…”