Endogenous nitric oxide modulates sympathetic neuroeffector transmission in the isolated rabbit lateral saphenous vein.
The rabbit isolated lateral saphenous vein (RLSV) has a heterogeneous population of alpha-adrenoceptors. Responses to electrical field stimulation, in the presence of cocaine, exhibit both alpha 1- and alpha 2-adrenoceptor-mediated components. The present study examined sympathetic neuroeffector transmission and the response to exogenous catecholamines after inhibition of nitric oxide (NO) synthesis with N omega-nitro-L-arginine methyl ester (L-NAME). A comparison of the response in the presence and absence of a functional endothelium was also carried out. L-NAME potentiated the first and second components of the response to nerve stimulation on the order of 300 and 500%, respectively. L-NAME also significantly potentiated responses to norepinephrine (NE), phenylephrine (PE), and UK 14304. Selective antagonism of the first phase was seen with prazosin (alpha 1-antagonist, 0.1 microM) and the second phase with rauwolscine (alpha 2-antagonist, 1 microM). In the presence of L-NAME, the remaining (uninhibited) components were potentiated. Removal of endothelial function induced by gentle rubbing of the intimal surface abolished potentiation to exogenous NE, PE, and UK14304 by L-NAME. However, a significant degree of potentiation of the neurogenic response was observed in the rubbed tissues in response to L-NAME. This suggests that there may be a nonendothelial source of NO that can modulate the neurogenic response to electrical field stimulation.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000068438:Brimonidine Tartrate; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D012501:Saphenous Vein / Q000294:innervation*; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D011810:Quinoxalines; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D009569:Nitric Oxide; D000068438:Brimonidine Tartrate; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine