title: Rapid tachyphylaxis to hemodynamic effects of PACAP-27 after inhibition of nitric oxide synthesis.
abstract: The vasodilator effects of pituitary adenylate cyclase-activating polypeptide (PACAP)-27 are subject to tachyphylaxis in rats treated with the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). We examined whether this tachyphylaxis could be prevented by administration of the putative endothelium-derived nitrosyl factor S-nitroso-L-cysteine (L-SNC) and whether L-SNC may exert its effects via increases in cGMP levels in vascular smooth muscle. Five doses of PACAP-27 (2 nmol/kg iv) produced pronounced vasodilator responses in saline-treated rats. These responses were not subject to tachyphylaxis. The first injection of PACAP-27 (2 nmol/kg iv) in L-NAME-treated (50 micromol/kg iv) rats produced vasodilator responses similar to those in saline-treated rats, whereas subsequent injections produced progressively smaller responses. The injection of L-SNC (1,200 nmol/kg iv) before each injection of PACAP-27 prevented tachyphylaxis to the Gs protein-coupled receptor agonist in L-NAME-treated rats, whereas equihypotensive doses of the NO donor sodium nitroprusside (100 micrograms/kg iv) did not. The injection of the membrane-permeant cGMP analog 8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphate (8-CPT-cGMP; 30 micromol/kg iv) to L-NAME-treated rats restored resting hemodynamic values to pre-L-NAME levels but did not prevent the development of tachyphylaxis to PACAP-27. These results suggest that nitrosyl factors prevent the development of tachyphylaxis to the hemodynamic actions of PACAP-27. These nitrosyl factors may act independently of their ability to generate cGMP in vascular smooth muscle.
authors.affiliation: Departments of Pharmacology and Psychology and Cardiovascular Center, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Whalen
authors.forename: M D
authors.initials: MD
authors.lastname: Travis
authors.forename: A K
authors.initials: AK
authors.lastname: Johnson
authors.forename: S J
authors.initials: SJ
authors.lastname: Lewis
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D003545:Cysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009479:Neuropeptides / Q000494:pharmacology*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051381:Rats; D017207:Rats, Sprague-Dawley; D026403:S-Nitrosothiols; D013618:Tachyphylaxis / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: C495403:Adcyap1 protein, rat; D004791:Enzyme Inhibitors; D009479:Neuropeptides; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D026403:S-Nitrosothiols; D013873:Thionucleotides; D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; C021315:S-nitrosocysteine; D006152:Cyclic GMP; D003545:Cysteine; D019331:NG-Nitroarginine Methyl Ester