Storage and release of labelled acetylcholine in the myenteric plexus of the guinea-pig ileum.
Guinea-pig ileum myenteric plexus-longitudinal muscle preparation was superfused with [3H]choline for 15 min either without being stimulated or during field stimulation at 0.1 or 16 Hz; the preparation was then either removed immediately or after 75- or 135-min superfusion with hemicholinium-3 (HC-3) and the total acetylcholine (ACh) and [3H]ACh contents were determined. For measuring the release of [3H]ACh the preparation was stimulated for 60 min the second time at 0.1 or 16 HZ in the presence of hemicholinium. Exposure to [3H]choline without stimulation resulted in the formation of [3H]ACh stores which were maintained in the first 75 min but decreased therafter. Labelling during stimulation at 16 Hz produced the largest and best maintained [3H]ACh content. Following labelling during 0.1-Hz stimulation, more label could be released than following labelling in the absence of stimulation. Labelling during 16-Hz stimulation did not increase any further in fool of [3H]ACh accessible to release by 0.1-Hz stimulation, but caused a 2.5 times increase in the pool from which Hz stimulation released [3H]ACh. These results suggest that two populations of cholinergic neurons exist in the myenteric plexus, one activated only by high frequency stimulation, the other by both high and low frequency stimulation.
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002794:Choline / Q000378:metabolism; D004558:Electric Stimulation; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism*; D066298:In Vitro Techniques; D009197:Myenteric Plexus / Q000378:metabolism* / Q000502:physiology; D009474:Neurons / Q000378:metabolism; D010275:Parasympathetic Nervous System / Q000378:metabolism; D013997:Time Factors
D002794:Choline; D000109:Acetylcholine