title: Acetylcholine inhibits nitric oxide (NO) synthesis in the gastropod nervous system.
abstract: Acetylcholine (ACh) is one of the main signals regulating nitric oxide synthase (NOS) expression and nitric oxide (NO) biosynthesis in mammals. However, few comparative studies have been performed on the role of ACh on NOS activity in non-mammalian animals. We have therefore studied the cholinergic control of NOS in the snail Helix pomatia and compared the effects of ACh on NO synthesis in the enteric nervous system of the snail and rat. Analyses by the NADPH-diaphorase reaction, immunocytochemistry, purification with ion-exchange chromatography, Western-blot, and quantitative polymerase chain reaction have revealed the expression of neuronal NOS in the rat intestine and of a 60-kDa subunit of NOS in the enteric nerve plexus of H. pomatia. In H. pomatia, quantification of the NO-derived nitrite ions has established that NO formation is confined to the NOS-containing midintestine. Nitrite production can be elevated by L-arginine but inhibited by N(omega)-nitro-L-arginine. In rats, ACh moderately elevates nitrite production, whereas ACh, the nicotinic receptor agonists (nicotine, acetyl thiocholine iodide, metacholine) and the cholinesterase inhibitor eserine reduce enteric nitrite formation in snails. The nicotinic receptor antagonist tubocurarine also provokes nitrite liberation, whereas the muscarinic receptor agonists or antagonists have no significant effect in snails. In the presence of EDTA or tetrodotoxin, ACh fails to inhibit nitrite production. In pharmacological studies, we have found that ACh contracts the midintestinal muscles and, in snails, simultaneously reduces the antagonistic muscle relaxant effect of L-arginine. Our experiments provide the first evidence for an inhibitory regulation of neuronal NO synthesis by ACh in an invertebrate species.
authors.affiliation: Department of Animal Anatomy and Physiology, Faculty of Science, Debrecen University, Debrecen, Hungary. roszer@med.unideb.hu
authors.forename: Tamás
authors.initials: T
authors.lastname: Roszer
authors.forename: Tamás
authors.initials: T
authors.lastname: Józsa
authors.forename: A József
authors.initials: AJ
authors.lastname: Szentmiklósi
authors.forename: Gáspár
authors.initials: G
authors.lastname: Bánfalvi
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D020869:Gene Expression Profiling; D006372:Helix, Snails / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D009415:Nerve Net / Q000187:drug effects / Q000201:enzymology; D009420:Nervous System / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D009538:Nicotine / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D009573:Nitrites; D009569:Nitric Oxide; D009538:Nicotine; D019001:Nitric Oxide Synthase; D000109:Acetylcholine; D014403:Tubocurarine