L-NAME pre-treatment partially inhibits the agmatine-evoked depression of the electrically induced twitch contraction of isolated rat vas deferens.
The effect of the putative endogenous ligand for alpha(2)-adrenoceptors and imidazoline receptors agmatine was studied in sympathetic neurotransmission in the rat epididymal vas deferens. Tissues were obtained from N(varpi)-nitro-l-arginine methyl ester (l-NAME)-treated or normal animals and were contracted by electrical stimulation or by exogenous adenosine 5'-triphosphate (ATP). In the electrically stimulated epididymal end, agmatine produced an inhibitory effect on twitch contraction that was partially reversed in l-NAME-treated animals, whereas the inhibition produced by clonidine was not affected by l-NAME treatment. The nitric oxide (NO)-donor S-nitroso-N-acetyl-penicillamine (SNAP) also inhibited twitch contraction. Neither agmatine nor SNAP interfered with the responses induced by exogenous ATP in the epididymal end. Removal of the epithelium of the preparation did not modify the agmatine response. We conclude that a nitrergic pathway activated by agmatine plays a role in its inhibitory effect in rat vas deferens, but it remains to be investigated whether it results from a direct action on the enzyme NO-synthase or a receptor-mediated mechanism.
Departamento de Farmacologia, UNIFESP, Escola Paulista de Medicina, Rua Botucatu, 862-Vila Clementino, CEP 04021-023, São Paulo, SP, Brasil. lugarcez.farm@epm.br
Lúcia
L
Garcez-do-Carmo
Wilson C
WC
Santos
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000376:Agmatine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004822:Epididymis / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects; D014649:Vas Deferens / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009569:Nitric Oxide; D000376:Agmatine; D026423:S-Nitroso-N-Acetylpenicillamine; D000255:Adenosine Triphosphate; D003000:Clonidine; D019331:NG-Nitroarginine Methyl Ester