Neurogenic contractions in intraocular porcine ciliary arteries are mediated by α2-adrenoceptors and NPY1 receptors and are inhibited by prostaglandin E2 acting on prejunctional EP4 receptors

Prostaglandin analogues and adrenergic drugs are used to reduce the intraocular pressure in glaucoma, which may partly be due to an effect on the tone of the intraocular arteries supplying the ciliary body. The aim of the present study was to investigate the interaction between prostaglandins and autonomic nervous activity induced by electrical stimulation of the tone in these ciliary vessels. The intraocular part of porcine ciliary arteries were isolated and mounted in a microvascular myograph for isometric tension recordings, and the effect of prostaglandin E2 on electrically induced contractions was studied in the presence of selective EP receptor antagonists. PGE2 induced concentration-dependent inhibition of electrically induced contractions of intraocular ciliary arteries which depended on the presence of the vascular endothelium. The effect of PGE2 was blocked by an EP4 receptor antagonist but not by an EP1 receptor antagonist. The neurogenic contractions were partially inhibited by an α2-adrenoceptor antagonist and totally inhibited by a NPY1 receptor antagonist. The effect of these antagonists was similar when contraction was induced by noradrenaline and NPY. Neurogenic contractions in intraocular porcine arteries are mediated by α2-adrenoceptors and NPY1 receptors and can be inhibited by PGE2 acting on prejunctional EP4 receptors. This contributes to a further understanding of the role of the autonomic nervous system and prostaglandins for regulating blood flow to the anterior segment of the eye.

► Tone changes in intraocular porcine ciliary arteries induced by electrical field stimulation. ► Contraction of intraocular porcine ciliary arteries is mediated by α2-adrenoceptors and NPY1 receptors. ► Contraction of intraocular porcine ciliary arteries is inhibited by PGE2 acting on prejunctional EP4 receptors.