In very low concentrations, Prostaglandin E2 affects the electrical and contractile activity of the smooth muscles of the gastric antrum, and this leads to a decrease in the potential polarization of the membrane, and the appearance of muscle contractions. Both calcium and sodium ions play an important role in the mechanism of the effect of prostaglandin E2 on this activity. The smooth muscles of gastric fundus do not show any spontaneous activity. Experiments have shown that prostaglandin E2 leads to the inhibition of the contraction produced by stimulation, but has the opposite effect on the gastric antrum. Calcium ions play an important role in this activity.