Endogenous acetylcholine release and labelled acetylcholine formation from [3H]choline in the myenteric plexus of the guinea-pig ileum.
The spontaneous release of acetylcholine (ACh) from the guinea-pig myenteric plexus - longitudinal muscle preparation superfused at a constant rate in the presence of physostigmine was 10 nmol-g-1-h-1. This release was decreased to one-third by tetradotoxin or by MnCl2 and increased 2.5 times by 0.1 Hz and 20 times by 16 Hz stimulation. The formation of [3H]ACh from [3H]choline increased from 3 to 33 nmol-g(-1)-h(-1) when the concentration of [3H]choline was increased from 1 muM to 50 muM. The rate of [3H]ACh formation was not affected by tetrodotoxin, MnCl2, or physostigmine in the absence of stimulation. It was increased by 50% by 0.1 Hz and by 100% by 16 Hz stimulation during the first 9 min of exposure to [3H]choline but not subsequently. The myenteric plexus - longitudinal muscle preparation contains 200 nmol/g choline. Results suggest that the apparent small [3H]ACh formation from low concentrations of [3H]choline is due to the dilution of [3H]choline by endogenous choline. The major part of [3H]ACh formation appears to be due to the intracellular turnover of ACh while the evoked release of [3H]ACh appears to originate from a small pool.
D000109:Acetylcholine / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D002794:Choline / Q000378:metabolism*; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism*; D066298:In Vitro Techniques; D008345:Manganese / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009197:Myenteric Plexus / Q000378:metabolism* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
D008345:Manganese; D013779:Tetrodotoxin; D002794:Choline; D000109:Acetylcholine