Different Sensitivities to α₁ Adrenoceptor Blockade on Periarterial Sympathetic Nerve-Induced Constriction by Low and High Frequencies in Canine Isolated Splenic Arteries

Abstract

The periarterial nerve electrical stimulation at 4 and 10 Hz induced a monophasic vasoconstriction of the canine splenic artery in a pulse number-related manner (1-30 pulses). The responses at 4 Hz were not significantly affected by 0.1 μM prazosin, but abolished by 1 μM α, β-methylene ATP. Prazosin (0.1 μM) partially but significantly inhibited responses at 10 Hz, and the remaining responses were blocked by 1 μM α, β-methylene ATP. It indicates that the monophasic vasoconstrictor response to short pulses of stimulation at a low frequency is mediated by P2X-receptors, whereas the response at a high frequency may be due to activation of not only P2X-receptors but also α₁ adrenoceptors.