Purpose:
We recently reported that intravenous infusion of adenosine increases aqueous production without changing ciliary blood flow. Thus, we were curious to determine the effects of inosine, the product of adenosine degradation, using the same protocol in the same preparation.
Methods:
This study used pentobarbital anesthetized rabbits (n=11, 2.2 ± 0.07 kg) in which the following variables were measured: mean arterial pressure (MAP), intraocular pressure (IOP), and orbital venous pressure (OVP) by direct cannulation, carotid blood flow by transit time ultrasound (BFcar, Transonic Systems TS420), heart rate (HR, digital cardiotachometer), ciliary blood flow by laser Doppler flowmetry (BFcil, Perimed PF 5000), and aqueous flow by fluorophotometry (Flow, Ocumetrics FM2). Measurements were made for 60-90 min before and during intravenous infusion of Ino (90 µg/min/kg). Results are presented as mean ± SE for the last 60 min of each time period. Responses were evaluated by 2-tailed paired t-tests.
Results:
Conclusions:
In contrast to intravenous adenosine, which increases aqueous production, intravenous inosine decreases aqueous production. Neither drug alters ciliary blood flow. The opposing effects on aqueous production are likely due to differential affinities for the different adenosine receptor subtypes present in the ciliary processes.
Keywords: adenosine • inflow/ciliary body • blood supply