Electrical and mechanical responses of uterine smooth muscle during anaphylaxis in vitro

Abstract

Female guinea pigs were injected with antigen (homologous sperm or ovalbumin) and 14–28 days later ileal segments and both uterine horns were removed. The ileal segments and one of the uterine horns from each animal were tested for responses to drugs, as well as to nonspecific and specific antigen; responses were recorded by means of a kymograph and muscle lever. The contralateral cornua were tested with nonspecific and with specific antigen as well as with drugs; responses were detected and recorded with intracellular electrodes and a mechanotransducer. The notable findings relative to the electronic studies were: within 1–2 minutes following exposure of the sensitized uterus to specific antigen there occurred a) a diminution in resting membrane potential; b) a sudden burst of action potential spikes; c) a contraction of the musculature which was of greater amplitude and of longer duration than those of the spontaneous contractions; d) during the sustained contracture phase, the rate of discharge of action potential spikes was higher than that accompanying spontaneous contractions. After desensitization, specific antigen was without effect. No effect of nonspecific antigen was observed in any of the preparations. After stimulating with specific antigen or with drugs, additional action potentials arose before repolarization from the previous action potential was completed.