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[Neuropeptide Y reduces desensitization of alpha 1-adrenoceptors in rat blood vessels].

Vasoconstrictive responses to norepinephrine (NE) in isolated rat aorta and renal artery were respectively taken to represent the biological responses mediated by alpha 1B and alpha 1A subtype adrenoceptor (AR). After blood vessels were incubated with 10 mumol/L NE for 2 h, alpha 1-AR mediated vasocontraction was desensitized significantly, alpha 1B-AR being more marked than alpha 1A-AR. In the presence of 0.5 mumol/L neuropeptide Y (NPY), desensitization of alpha 1B-AR was attenuated significantly. In rat aorta the NE-mediated contraction comprised both phasic and tonic elements. After the incubation with NE, the phasic contraction period was prolonged but magnitude decreased, while no change was found for the tonic contraction. In the presence of NPY, the changes of phasic contraction caused by NE preincubation disappeared. It is suggested that retardation and reduction of intracellular Ca2+ release were involved in the mechanism for desensitization of alpha 1B-AR.