title: Cannabinoid 1 (CB1) receptors coupled to cholinergic motorneurones inhibit neurogenic circular muscle contractility in the human colon.
abstract: The effects of cannabinoid subtype 1 (CB(1)) receptor activation were determined on smooth muscle, inhibitory and excitatory motorneuronal function in strips of human colonic longitudinal muscle (LM) and circular muscle (CM) in vitro. Electrical field stimulation (EFS; 0.5-20 Hz, 50 V) evoked a relaxation in LM and CM precontracted with a neurokinin-2 (NK-2) selective receptor agonist (beta-ala(8)-neurokinin A; 10(-6) M) in the presence of atropine (10(-6) M); this was unaltered following pretreatment with the CB(1)-receptor selective agonist arachidonyl-2-chloroethylamide (ACEA; 10(-6) M). In the presence of nitric oxide synthase blockade with N-nitro-L-arginine (10(-4) M), EFS evoked a frequency-dependent 'on-contraction' during stimulation and an 'off-contraction' following stimulus cessation. On-contractions were significantly inhibited in CM strips by pretreatment with ACEA (10(-6) M). These inhibitory effects were reversed in the presence of the CB(1) receptor-selective antagonist N-(piperidine-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (10(-7) M). ACEA did not alter LM or CM contractile responses to acetylcholine or NK-2 receptor-evoked contraction. Immunohistochemical studies revealed a colocalisation of CB(1) receptors to cholinergic neurones in the human colon based on colabelling with choline acetyltransferase, in addition to CB(1) receptor labelling in unidentified structures in the CM. In conclusion, activation of CB(1) receptors coupled to cholinergic motorneurones selectively and reversibly inhibits excitatory nerve transmission in colonic human colonic CM. These results provide evidence of a direct role for cannabinoids in the modulation of motor activity in the human colon by coupling to cholinergic motorneurones.
authors.affiliation: School of Chemical & Biomedical Sciences, Faculty of Arts Health & Sciences, Central Queensland University, Bruce Highway, Rockhampton, QLD 4702, Australia.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Hinds
authors.forename: Katja
authors.initials: K
authors.lastname: Ullrich
authors.forename: Scott D
authors.initials: SD
authors.lastname: Smid
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D001095:Arachidonic Acids / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008875:Middle Aged; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors / Q000502:physiology*; D018041:Receptors, Neurokinin-2 / Q000037:antagonists & inhibitors / Q000502:physiology
chemical_list: D001095:Arachidonic Acids; D004791:Enzyme Inhibitors; D018727:Muscarinic Antagonists; D043884:Receptor, Cannabinoid, CB1; D018041:Receptors, Neurokinin-2; C119325:arachidonyl-2-chloroethylamide; D019335:Nitroarginine; D001285:Atropine; D019001:Nitric Oxide Synthase; D000109:Acetylcholine