Abstract
Gastric smooth muscle generates slow waves spontaneously, and they are regulated by autonomic nerves. Experiments were carried out to investigate the effects of hypoxia on spontaneous electrical activity and their autonomic neuronal regulation in smooth muscle of the guinea-pig stomach. Segments of smooth muscle tissues were isolated from the antrum region of the stomach, and electrical activities of smooth muscle cells were recorded using conventional microelectrode technique. Junction potentials produced by transmural nerve stimulation were also recorded. Isometric mechanical responses of smooth muscle tissue were also examined. Low oxygen condition, produced by bubbling with N2-gasses, induced a reduction in resting tension, spontaneous rhythmic contractions and mechanical responses produced by nerve stimulation, with no significant alteration to the frequency of spontaneous contraction. These changes were not associated with change in electrical responses of the membrane (the resting membrane potential, shape of slow waves and junction potentials). Acetylcholine (Ach)-induced depolarization and contraction responses were also not changed significantly during hypoxia. The results suggest that oxygen requirement for mitochondrial activity responsible for production of rhythmic activity is relatively low. [Jpn J Physiol 55 Suppl:S118 (2005)]
