Role of calcium ions and of the cholinergic system in the contractile effects of prostaglandin F2 alpha on intestinal smooth muscle (experiments on cat jejunum).
The cumulative contractile effect of prostaglandin F2 alpha (PGF2 alpha) on isolated longitudinal muscle of cat jejunum has been studied at different Ca-content in the nutrient solution (2.5, 1.0 and 6.25 mM) and on the background of pretreatment with physostigmine and atropin. PGF2 alpha contracts in a dose-dependent degree the longitudinal muscle of the jejunum. The maximum contractile effect of PGF2 alpha (1 x 10(-7)M) increases upon reducing the extracellular calcium (1.0 mM) and decreases when the Ca-concentration is increased to 6.25mM. Similar changes in the PGF2 alpha effect for the Ca-concentration used have also been observed after pretreatment of the preparations with physostigmine (1 x 10(-8)M). The contractile effect of PGF2 alpha considerably decreases on the background of atropin action (1 x 10(-8)M). The inhibitory action of atropin on the PGF2 alpha-induced contraction decreases upon increasing the Ca-concentration in the nutrient solution. The results suggest participation of the cholinergic system in the realization of the PGF2 alpha effect. The possibility of modulating this effect by the calcium regulatory mechanisms of the muscle is discussed.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002415:Cats; D015237:Dinoprost; D066298:In Vitro Techniques; D007583:Jejunum / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D010275:Parasympathetic Nervous System / Q000502:physiology*; D010830:Physostigmine / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology*
D011460:Prostaglandins F; D001285:Atropine; D010830:Physostigmine; D015237:Dinoprost; D002118:Calcium