The nature of the acetylcholine and 5-hydroxytryptamine receptors in buccal smooth muscle of the pest slug Deroceras reticulatum.
The characteristics of the acetylcholine (ACh) and 5-hydroxytryptamine (5-HT) receptors of Deroceras buccal muscle were examined using specific pharmacological probes and sucrose gap electrophysiological analysis. ACh induced concentration-dependent smooth tonic contractures coupled with considerable depolarisation from the normal resting membrane potential of -30.6 mV. The use of choline ester analogues such as carbachol, propionylcholine and butyrylcholine, specific cholinergic agonists such as nicotine, muscarine, bethanecol and pilocarpine and antagonists such as d-tubocurarine, succinylcholine, hexamethomium, atropine, gallamine, pirenzepine and scopolamine indicated that the ACh receptor showed both nicotinic and muscarinic characteristics; the muscarinic activity resembled that of a mammalian M(2)-like receptor. Alternatively, it can not be ruled out that both mammalian types of receptor may be present in this preparation since both nicotine and muscarine induced noticeable tension. 5-HT application induced characteristic dose-dependent phasic contractions accompanied by small but quite consistent depolarisations. Serotonergic agonist and antagonist experiments using 1-(3-chlorophenyl) piperazine, 1-(m-chlorophenyl) biguanide, methiothepin, methysergide and metoclopramide strongly suggested that the 5-HT receptor showed closest pharmacological affinity with the 5-HT(1) receptor class of mammals but with some 5-HT(2) activity. In view of the phylogenetic gap between molluscs and mammals it is not surprising that the ACh and 5-HT receptors of Deroceras can not be properly classified by conventional mammalian terminology.
Wright
T J
TJ
Department of Biological Sciences, Institute of Environmental and Natural Sciences, Lancaster University, Lancaster LA1 4YQ, UK.
Huddart
H
H
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002794:Choline / Q000031:analogs & derivatives; D004952:Esters / Q000494:pharmacology; D005703:Gallamine Triethiodide / Q000494:pharmacology; D018738:Hexamethonium / Q000494:pharmacology; D008974:Mollusca / Q000502:physiology*; D009055:Mouth; D018721:Muscarinic Agonists / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D010890:Pirenzepine / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000502:physiology*; D011978:Receptors, Nicotinic / Q000502:physiology*; D011985:Receptors, Serotonin / Q000502:physiology*; D012601:Scopolamine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D013390:Succinylcholine / Q000494:pharmacology; D014403:Tubocurarine / Q000494:pharmacology
D004952:Esters; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D018738:Hexamethonium; D010890:Pirenzepine; D009538:Nicotine; D001285:Atropine; D012601:Scopolamine; D013390:Succinylcholine; D002794:Choline; D000109:Acetylcholine; D005703:Gallamine Triethiodide; D014403:Tubocurarine