Effect of neuropeptide Y on adrenergic and non-adrenergic, non-cholinergic responses in the rat anococcygeus muscle.
1. The effects of neuropeptide Y (NPY) were examined on adrenergic and non-adrenergic, non-cholinergic (NANC) neurotransmission in the rat anococcygeus muscle. 2. NPY (0.1-0.3 microM) greatly potentiated the contractile responses induced by field stimulation. Prazosin (0.1 microM) completely abolished the stimulation-induced responses either in the absence or presence of NPY. 3. NPY (0.1-0.3 microM) enhanced only the contractile responses to low doses of noradrenaline (NA, 0.003-0.01 microM). Responses to tyramine were unaffected by the same concentrations of NPY. 4. In superfused anococcygeus, previously loaded with [3H]-NA, NPY (0.1-0.3 microM) failed to modify the basal, as well as the stimulation-evoked, release of tritium at 2 and 4 Hz. 5. NANC relaxations induced by electrical stimulation were significantly reduced, in a concentration-related manner, by 0.1-0.3 microM NPY. 6. L-NG-nitro-arginine (L-NOARG, 30 microM) enhanced the stimulation (0.25-1 Hz)-induced motor responses. In the presence of L-NOARG (30 microM), NPY (0.1 microM) did not modify the motor responses induced by field stimulation (0.25-0.5 Hz). L-Arginine did not reverse the NPY-induced potentiation of stimulation-induced motor responses. 7. The relaxations of anococcygeus muscle induced by sodium nitroprusside (SNP, 0.01-0.3 microM) were diminished by NPY (0.1-0.3 microM). 8. Our study suggests that NPY, at concentrations devoid of contractile effect, potentiates the motor responses of rat anococcygeus muscle as a consequence, at least in part, of the inhibition of NANC relaxing responses by a different mechanism from L-NOARG.
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Departament de Farmacología i Psiquiatria, Universitat Autònoma de Barcelona, Spain.
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D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009132:Muscles / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D009478:Neuropeptide Y / Q000494:pharmacology*; D019335:Nitroarginine; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*; D014439:Tyramine / Q000494:pharmacology
D009478:Neuropeptide Y; D019335:Nitroarginine; D001120:Arginine; D009638:Norepinephrine; D014439:Tyramine; D011224:Prazosin