EFFECT OF DRUGS AND ELECTRICAL FIELD STIMULATION ON CIRCULAR MUSCLE STRIPS FROM HUMAN LOWER OESOPHAGUS

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Abstract
Sphincteric muscle from human lower oesophagus may be identifiable in vitro by its ability to develop a very high level of tone (sustained resting tension). Circular muscle strips from human lower oesophagus generally behave in a similar manner to strips from the opossum oesophagus with respect to development of tone, responses to electrical field stimulation and responses to a variety of drugs. Pharmacological analysis of responses to field stimulation in strips from the region of the oesophago-gastric junction suggests that the typical biphasic response (relaxation followed by an after-contraction) is mediated by nerves which are neither adrenergic nor cholinergic. Of the substances examined only vasoactive intestinal peptide (VIP) cannot be excluded as a possible candidate for the role of inhibitory transmitter. The mechanism producing the after-contraction is not clear but it would seem unlikely that this is simply a rebound contraction. The after-contraction can be blocked independently of the relaxation by a variety of agents and is potentiated by metoclopramide.