Hypercapnia Impairs Vascular Responses to Changes in Ocular Perfusion Pressure in Rat Retina

Abstract

Purpose : Retinal vascular resistance is constantly regulated by both myogenic and metabolic mechanisms. While most studies have investigated these mechanisms separately, how they interact to impact the vascular resistance is unclear. We considered whether hypercapnia (HC) modified the effect of ocular perfusion pressure (OPP) lowering, induced by lowering blood pressure (BP) or increasing intraocular pressure (IOP) on retinal vessel diameter (Ø). Methods : In pentobarbital anesthetized Brown Norway rats, breathing ~30% O2 air, normocapnia (NC) and hypercapnia (HC) were achieved by controlled ventilation. A gradual decrease in OPP, at the same rate for BP lowering or IOP elevation, was indu..