Action of different agonists and antagonists of the cholinergic system on the rat lower esophageal sphincter.

Several compounds acting on the cholinergic system at different levels were tested for their stimulatory or inhibitory effects on the isolated lower esophageal sphincter (LES) of the rat. Results obtained with acetylcholine, bethanechol and compound McN-A343 on the one hand and atropine, pirenzepine, ganglion blocking agents and tetrodotoxin on the other, suggested that LES contraction was associated mainly with the stimulation of post-synaptic muscarinic receptors. Nicotinic receptors (both ganglionic and muscular) seem to have a minor role, if any.