Characterisation of the prejunctional inhibitory muscarinic receptor on cholinergic nerves in the rat urinary bladder.
The nature of the prejunctional inhibitory muscarinic receptor on cholinergic nerve endings in the rat urinary bladder was investigated by measuring stimulated endogenous acetylcholine release via high pressure liquid chromatography (HPLC), in the presence of various selective muscarinic antagonists. The rank order of potencies for the antagonists used was: atropine (-log concentration = 7.8) > 4-DAMP (4-diphenylacetoxy-N-methylpiperidine) (7.6) > tripitramine (7.3) = HHD (hexahydrodifenidol) (7.3) > pFHHSiD (p-fluoro-hexahydrosiladifenidol hydrochloride) (7.0) > himbacine (6.5) > methoctramine (5.9) > or = pirenzepine (5.8) > gallamine (4.3). A comparison of the antagonist potencies obtained, with affinity constants at muscarinic M(1) to M(5) receptors, suggests that the prejunctional inhibitory muscarinic receptor is of the M(4) receptor subtype.
Department of Pharmaceutical Biology and Pharmacology, Victorian College of Pharmacy, Monash University, 381 Royal Parade, Parkville, 3052, Victoria, Australia. Albert.Shen@vcp.monash.edu.au
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D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002799:Cholinergic Fibers / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004558:Electric Stimulation; D005260:Female; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010890:Pirenzepine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D043588:Receptor, Muscarinic M4; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism*
D018727:Muscarinic Antagonists; D043588:Receptor, Muscarinic M4; D011976:Receptors, Muscarinic; D010890:Pirenzepine; D000109:Acetylcholine