The effects of drugs and electrical field stimulation on the human lower oesophageal sphincter.

Acetylcholine, bethanechol, pentagastrin and dopamine contracted muscle strips cut transversely from the human lower oesophageal sphincter (LOS). In the presence of hyoscine the contraction to acetylcholine was changed to a relaxation; tolerance was observed to the effect of pentagastrin. Metoclopramide and adenosine triphosphate were only partially effective on LOS muscle, some strips were unresponsive, others gave small contractions. Noradrenaline, dimethylphenylpiperazinium and histamine relaxed LOS muscle, relaxations to noradrenaline were blocked by propranolol. In contrast to drug action the response of LOS muscle to electrical field stimulation was dependent on the exact origin of the muscle strip. Muscle cut adjacent to the oesophagogastric junction only relaxed, strips cut progressively more rostral to this point showed a biphasic response with the after contraction becoming more obvious as the distance from the oesophagogastric junction increased. Relaxation of LOS muscle to electrical field stimulation appeared to involve non-adrenergic non-cholinergic nerves. It is suggested that muscle obtained from the terminal oesophagus may be identified as the LOS if it responds to electrical field stimulation with only a relaxation.