Adenosine A1 receptor agonist GR79236 suppresses apnea during all sleep stages in the rat

We tested the hypothesis that N-[(1S, trans)-2-hydroxycyclopentyl]adenosine (GR79236), a novel adenosine A1 receptor agonist, would suppress sleep-related apnea in the rat at doses not associated with hypotension or hypothermia. Nine adult Sprague-Dawley rats were instrumented for chronic recording of sleep by electroencephalographic and electromyographic monitoring. Respirations were measured by single chamber plethysmograph, and blood pressure and heart period were transduced by a telemetric implant. Each rat was polygraphically recorded for 6 hours on four occasions in random order, with recordings for an individual animal separated by at least 3 days. Fifteen minutes prior to each recording (0945 hours) each animal received a 1 ml/kg intraperitoneal bolus injection of one of four injectates: saline (control) or 0.03 mg/kg, 0.3 mg/kg, or 3 mg/kg of GR79236. The study was a repeated-measures balanced design such that each animal was recorded exactly once for each injectate. The rate of spontaneous apneas (pauses > 2.5 seconds) was significantly reduced during all sleep stages by all doses of GR79236. At the highest dose, apnea index was reduced by over 70% in both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. In contrast, GR79236 had no effect on sleep stage volumes or blood pressure at any dose tested. Heart rate and core temperature were reduced only at the highest dose (3 mg/kg). We conclude that the adenosine A1 receptor agonist GR79236 significantly suppresses apnea expression in all sleep stages at doses not associated with significant changes in sleep architecture, blood pressure, heart rate, or core temperature.