Contribution of external Ca2+ to the modulation by prostaglandin E2 of the release of acetylcholine from the myenteric plexus of guinea pig ileum.
The effects of external concentration of Ca2+ [( Ca2+]o) on the modulation by indomethacin (IND) or prostaglandin E2 (PGE2) of the evoked release of acetylcholine (ACh) were investigated in the myenteric plexus of guinea pig ileum. An increase in the [Ca2+]o from 0.45 to 3.6 mM depressed both the spontaneous and the nicotine-induced release of ACh, while the releases of ACh induced by electrical-field stimulation (EFS) or by high K+ were augmented. IND and PGE2 did not modify the release of ACh induced by EFS and high K+, at any given [Ca2+]o tested. The nicotine-induced release of ACh was significantly inhibited by IND with no relation to [Ca2+]o, and these inhibitory effects of IND were prevented by PGE2. At 0.45 mM [Ca2+]o, the extent of the recovery by PGE2 was less potent than those at other [Ca2+]o. IND inhibited the spontaneous release of ACh at lower [Ca2+]o, and such inhibition was not observed in the presence of PGE2. Thus, the modulatory actions of PGE2 on the spontaneous and the nicotine-induced release of ACh may depend partially on [Ca2+]o.
Takeuchi
T
T
Department of Veterinary Pharmacology, Faculty of Agriculture, University of Osaka Prefecture, Sakai, Japan.
Shimizu
M
M
Okuda
M
M
Yagasaki
O
O
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D015232:Dinoprostone / Q000502:physiology*; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009197:Myenteric Plexus / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology
D009538:Nicotine; D015232:Dinoprostone; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium; D007213:Indomethacin