Effect of neuropeptide Y on alpha 2-adrenoceptor-mediated cardiovascular responses in the pithed rat.
1. The effects of neuropeptide Y (NPY) on the cardiovascular responses induced by stimulation of pre and postjunctional alpha 2-adrenoceptors were studied in the pithed normotensive rat. 2. The increase in diastolic blood pressure induced by cumulative injection of xylazine (1-1000 micrograms kg-1, i.v.) were potentiated by NPY (5 micrograms kg-1) but not affected by a lower dose (0.75 micrograms kg-1) of this peptide. 3. Xylazine (1-100 micrograms kg-1) inhibited in a dose-dependent manner the tachycardia induced by continuous electrical stimulation (0.2 Hz, 2 ms, 60 V) of the spinal cord (C7-Thl). 4. NPY (5 micrograms kg-1 but not 0.75 micrograms kg-1) enhanced the inhibitory effect of xylazine on the tachycardia induced by electrical stimulation without having any direct effect on heart rate. 5. These results suggest that there may be a positive interaction between NPY receptors, postjunctional alpha 2-adrenoceptors and between NPY receptors and postjunctional alpha 2-adrenoceptors in the cardiovascular system of the rat.
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Department de Farmacologia i Psiquiatria, Universitat Autonoma de Barcelona, Bellaterra, Spain.
Macrae
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D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003655:Decerebrate State; D004558:Electric Stimulation; D006207:Half-Life; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009478:Neuropeptide Y / Q000494:pharmacology*; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D014991:Xylazine / Q000494:pharmacology
D009478:Neuropeptide Y; D011942:Receptors, Adrenergic, alpha; D014991:Xylazine