Neurotransmitted effect of prostaglandin F2 alpha in isolated cat jejunum.

Prostaglandin F2 alpha (PGF2 alpha) (1 nM-0.1 microM) increased the amplitude of the spontaneous phasic contractions and produced tonic contraction of the isolated longitudinal muscle from the cat jejunum. The amplitude of the electrically-induced contractions increased by PGF2 alpha (1 nM-10 nM) in a dose-dependent degree. PGF2 alpha decreased the inhibitory effect of indomethacin (30 microM) on the contractile response to electrical stimulation. Hexamethonium did not influence the PGF2 alpha effect on the electrically-induced contractions but inhibited the PGF2 alpha-produced tonic contractions. The contractile effect of PGF2 alpha depended on the number of impregnated nerve cells and terminals preserved in the preparations long after dissection. The data suggest that PGF2 alpha increases the acetylcholine release and that there is a "stepwise" action of PGF2 alpha on the transmitter release from the postganglionic or preganglionic cholinergic terminals depending on the PGF2 alpha concentration and leading to phasic or tonic smooth-muscle contractions.