Cholinergic-mediated secretion in the rat colon: neuronal and epithelial muscarinic responses.
The acetylcholine receptor agonists, acetylcholine (10(-5)-10(-4 M), carbachol (5 x 10(-6)-5 x 10(-5) M), bethanechol (5 x 10(-5)-5 x 10(-4) M) and dimethylphenylpiperazinium (DMPP, 10(-5) M) increased the short-circuit current (Isc) in the rat colon descendens by a tetrodotoxin (TTX)-sensitive mechanism. Blockade by TTX was still observed after removal of the submucosa, indicating the involvement of neurons of the mucosal plexus. Hexamethonium (10(-5) M) and atropine (10(-6) M) were used to distinguish between nicotinic and muscarinic neuronally mediated effects. The inhibitor of choline uptake, hemicholinium-3 (1 mM), reversibly inhibited the effect of repeated electric field stimulation (EFS). The EFS response was only inhibited by high concentrations of atropine (greater than or equal to 10(-5) M). In mucosa-submucosa preparations 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) was more effective than telenzepine whereas pirenzepine was ineffective. Pirenzepine inhibited the EFS response in mucosa preparations as did telenzepine and 4-DAMP. It was not possible to differentiate between the muscarinic receptors involved in the different parts of the enteric nervous system on the basis of our results.
Diener
M
M
Institut für Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg-Saar, F.R.G.
Knobloch
S F
SF
Bridges
R J
RJ
Keilmann
T
T
Rummel
W
W
D000109:Acetylcholine / Q000502:physiology*; D000818:Animals; D003106:Colon / Q000378:metabolism*; D004558:Electric Stimulation; D004848:Epithelium / Q000502:physiology; D005260:Female; D009116:Muscarine / Q000494:pharmacology; D009474:Neurons / Q000648:ultrastructure; D010276:Parasympatholytics / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000502:physiology; D011976:Receptors, Muscarinic / Q000502:physiology; D011978:Receptors, Nicotinic / Q000502:physiology; D013368:Submucous Plexus / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D010276:Parasympatholytics; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; D013779:Tetrodotoxin; D009116:Muscarine; D000109:Acetylcholine