Prostaglandin-mediated inhibition of noradrenaline release: V. A comparison of the neuroinhibitory effect of three prostaglandins: E2, I2, and 6-keto-PGF1alpha.

The effect of PGE2, PGI2, and 6-keto-PGF1alpha respectively on the contractile response of the isolated, field-stimulated guinea pig vas deferens was investigated. All three PGs were capable of inhibiting the contractile responses of the vas deferens, but the concentrations required varied considerably: PGE2 was about 700 times more active than PGI2 and about 4600 times more active than 6-keto-PGF1alpha in this respect. It is suggested that PGI2, although formed in tissues with sympathetic innervation, does not play a physiological role as inhibitor of sympathetic transmitter release.