How far from the stimulation site in myenteric plexus-longitudinal muscle preparations the neurogenic cholinergic...

Neurogenic contractions of a segment of myenteric plexus-longitudinal muscle strip preparations from the guinea-pig ileum were evoked. The site of electric stimulation was separated from the contracting segment by a gap preventing the spread of muscle action potentials set up in other regions. The width of the separating gap (2-20 mm) indicated the length of nerve fibers that could conduct impulses across and trigger cholinergic contractions behind the gap; it was more than 12 and less than 16 mm. Transmission of excitation was more effective in the aboral direction compared to the oral direction and was not apparently affected by noradrenaline nor by substance P.