Effects of R-28935 on sympathetic nervous activity in anesthetized cat.

Intravenous administration of erythro-1-(1-[2-(1,4-benzodioxan-2-yl)-2-OH-Et]-4-piperidyl)-2-benzimidazolinone (R-28935) (25--100 microgram/kg) produced a dose-related decrease in spontaneous electrical activity recorded in the splanchnic and renal nerves. Reductions in sympathetic nerve activity were paralleled by hypotension and bradycardia. R 28935-induced depressor responses were not affected by baroreceptor denervation, piperoxan, yohimbine or phentolamine. Results support the idea that R-28935 decreased resting blood pressure and heart rate through a reduction in central sympathetic outflow which does not involve alpha-adrenergic receptor activation.