The effects of prostaglandins on guinea-pig isolated intestine and their possible contribution to muscle activity and tone.

1 Prostaglandins F(1alpha) and F(2alpha) caused contraction of the longitudinal muscle of both guinea-pig isolated ileum and colon, apparently by acting directly on the muscle and on cholinergic nerves. They had little effect on ileal circular muscle.2 Prostaglandins E(1) and E(2) caused contraction of the longitudinal muscle of guinea-pig isolated colon, apparently by acting directly on the muscle and on excitatory nerves which are non-cholinergic. Prostaglandin E(1) seems more effective than E(2) in stimulating these nerves.3 It seems likely that prostaglandin release in vitro maintains the tone of the longitudinal muscle of guinea-pig colon, whereas release of a prostaglandin E compound inhibits circular muscle tone.