Effects of Disruption of Gap–Junction Communication on Autoregulatory Mechanism in the Optic Nerve Head Blood Flow

Abstract

Abstract: : Purpose: To evaluate effects of disruption of gap–junction communication on autoregulatory mechanism in the optic nerve head (ONH) blood flow in rabbits. Methods: Octanol (1.0, 3.0 and 10.0 mM), a gap–junction uncoupler, was injected into the posterior vitreous of rabbits, allowing for 2 hours for the distribution of the drug to the retina; while balanced saline solution (BSS) was injected intravitreally in the control. Then, intraocular pressure (IOP) was artificially elevated from the baseline of 20 to 50 and 70 mmHg by increasing the height of the bottle of BSS, which was connected into the vitreous cavity with infusion canulae through pars plana. IOP levels were monitored with a pressure transducer and maintained at each level for 30 minutes. Changes of capillary blood flow in the ONH in response to IOP elevation were measured by laser speckle methods in 10 minutes time intervals. Results: Intravitreal octanol had a tendency to induce a reduction of ONH blood flow in response to IOP elevation in a dose dependent way, and it significantly decreased ONH blood flow at a dose of 10 mM compared to the control (P<0.01, ANOVA) during the periods of IOP elevation, while ONH blood flow was well preserved in the control. On the other hand, intravitreal octanol alone (10 mM) did not reduce ONH blood flow in the eyes of rabbits with normotension throughout the 4 hours’ observation period following the injection. Conclusions: These results indicate that gap–junction communication may play an important role in the autoregulation in the ONH blood flow, and impairment of the connection may lead to insufficient blood flow in the ONH when IOP is elevated.

Keywords: blood supply • gap junctions/coupling • optic disc