General pharmacology of SDZ WAG 994, a potent selective and orally active adenosine A1 receptor agonist

The pharmacological properties of 6-cyclohexyl-2′-0-methyladenosine (SDZ WAG 994)—a potent, selective, and orally active adenosine A₁ receptor agonist—are described. SDZ WAG 994 is a potent (K_D 23 ± 2 nM, n = 5) and selective (1,090-fold vs. A_2A receptors) displacer of binding to pig striatal A₁ receptors and behaves as a full agonist at the A₁ receptors coupled negatively to adenylate cyclase in rat adipocytes (pEC₅₀ 6.4 ± 0.2, n = 3), those which induce contraction of rat spleen (pEC₅₀ 7.1 ± 0.1, n = 13) and those which suppress the response to autonomic nerve stimulation in guinea-pig ileum (pIC₅₀ 6.6 ± 0.1, n = 4) and rat kidney (pIC₅₀ 6.0 ± 0.1, n = 6). The compound has negligible affinity (pEC₅₀ < 4, n = 5) for the A_2B receptor which mediates relaxation of guinea-pig aorta. In spontaneously hypertensive (SH) rats SDZ WAG 994, 0.05–0.5 mg/kg (0.14–1.4 μmol/kg) po, caused dose-related and sustained (> 5 h) falls in blood pressure (BP) and heart rate (HR) and suppressed plasma renin activity (PRA); the cardiovascular effects could be immediately and fully reversed by an intravenous injection of 8-(p-sulphophenyl)theophylline, 20 mg/kg (56.4 μmol/kg). SDZ WAG 994 given via the food at 0.4 and 1.2 mg/kg/day (1.1 and 3.3 μmol/kg/day) for 7 or 14 days, respectively, induced dose-related hypotension and bradycardia which were well maintained throughout the treatment periods. In the conscious, normotensive dog, SDZ WAG 994, 1 and 3 mg/kg (2.8 and 8.3 μmol/kg) po, induced substantial, sustained falls in BP which were accompanied by tachycardia. In salt depleted squirrel monkeys, SDZ WAG 994, 0.1–0.3 mg/kg (0.28–0.83 m?mol/kg) iv or 0.2–0.6 mg/kg (0.56–1.7 μmol/kg) po caused dose-related and sustained (> 5 h) bradycardia and suppression of PRA but no change in BP. In rhesus monkeys, SDZ WAG 994, 0.1–1.2 mg/kg (0.28–3.3 μmol/kg) po induced sustained bradycardia and suppression of PRA and the plasma free fatty acid and triglyceride concentrations. The data establish SDZ WAG 994 as a potent, selective, and orally active adenosine A₁ receptor agonist with therapeutic potential in certain cardiovascular and/or metabolic disease states. © 1995 Wiley-Liss, Inc.