title: Nitric oxide control of large veins in the toad Bufo marinus.
abstract: This study examined the nitric oxide (NO) control of the vascular smooth muscle of the ventral abdominal vein and vena cava of the toad, Bufo marinus, by using anatomical and physiological approaches. Nicotinamide adenine di-nucleotide phosphate-diaphorase histochemistry and immunohistochemistry using endothelial nitric oxide synthase (NOS) and neural NOS antibodies produced no evidence for endothelial NOS in the veins, but, neural NOS-immunoreactive perivascular nerves were present. Acetylcholine (10(-5) M) caused a vasodilation in both veins that was endothelium-independent, and which was blocked by the soluble guanylyl cyclase inhibitor, ODQ (10(-5) M). The NOS inhibitors, L-NNA (10(-4) M) and L-NAME (10(-4) M), did not significantly reduce the vasodilatory effect of acetylcholine in the veins; this suggested that the vasodilation was not due to NO. However, in the presence of phenoxybenzamine (10(-7)-10(-8) M), L-NNA significantly reduced the vasodilatory effect of acetylcholine in the veins. This unusual response is due to phenoxybenzamine partially inactivating the muscarinic receptor pool in the veins. In addition, the neural NOS inhibitor, vinyl-L-NIO (10(-5) M), significantly reduced the acetylcholine-mediated vasodilation in the presence of phenoxybenzamine. The results show that in toad veins, nitrergic nerves rather than an endothelial NO system are involved in NO-mediated vasodilation.
authors.affiliation: School of Biological and Chemical Sciences, Deakin University, Geelong, VIC 3217, Australia.
authors.forename: Brad R S
authors.initials: BR
authors.lastname: Broughton
authors.forename: John A
authors.initials: JA
authors.lastname: Donald
mesh_terms: D000005:Abdomen / Q000098:blood supply; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002024:Bufo marinus / Q000502:physiology*; D005260:Female; D008297:Male; D009252:NADPH Dehydrogenase / Q000032:analysis; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000276:immunology / Q000378:metabolism; D026602:Nitrergic Neurons / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000276:immunology / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D010643:Phenoxybenzamine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects; D014680:Veins / Q000187:drug effects / Q000502:physiology*; D014684:Venae Cavae / Q000187:drug effects / Q000502:physiology*
chemical_list: D009419:Nerve Tissue Proteins; D010643:Phenoxybenzamine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496316:Nos3 protein, rat; D009252:NADPH Dehydrogenase; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester