Cardiovascular and renal actions of AHR-16303B, an antagonist of 5-HT2 receptors and calcium channels, in hypertensive and normotensive rats.

The cardiovascular and renal responses to AHR-16303B, a novel antagonist of 5-hydroxytryptamine (5-HT2) receptors and calcium channels, were examined in spontaneously hypertensive (SHR) and normotensive rats (NTR) and compared with verapamil and ritanserin. In SHR, AHR-16303B (10-300 mg/kg orally, p.o.) produced dose-related reductions in mean arterial blood pressure (MABP), accompanied by modest isokaliuretic diuresis and unchanged heart rate (HR). In NTR, 10-30 mg/kg p.o. AHR-16303B had no effect on MABP or renal excretory function; 100 and 300 mg/kg reduced MABP but had only transient effects on HR; 100 mg/kg produced antidiuresis in NTR. Both strains of rats tolerated doses of AHR-16303B as high as 300 mg/kg. In both SHR and NTR, verapamil (10-100 mg/kg p.o.) produced dose-related reductions in MABP, antinatriuresis at 60 and 100 mg/kg, and variable effects on HR. Oral ritanserin had no effect on MABP of SHR or NTR at 3 or 10 mg/kg. AHR-16303B is unique in that it simultaneously antagonizes 5-HT2 receptors and produces safe and effective reduction of elevated BP without altering HR or triggering renal compensatory antidiuresis. At effective 5-HT2/calcium antagonistic doses, AHR-16303B has no effect on cardiorenal homeostasis in normotensive animals.