Facilitation of sympathetic neurotransmission in the rat anococcygeus muscle by prostaglandins D2 and F2 alpha.

1 Investigations were made into the effects of prostaglandins D2 (PGD2) and F2 alpha (PGF2 alpha) on the responses of the rat anococcygeus muscle to field stimulation of intrinsic motor (sympathetic) and inhibitory nerves, and to exogenous noradrenaline. 2 PGD2 (2.8 X 10(-6) mol/1) substantially increased the motor responses to field stimulation at all frequencies tested (2 to 32 Hz), and caused a smaller increase in the responses to noradrenaline. 3 PGF2 alpha (2.8 X 10(-6) mol/1) strongly potentiated the motor responses to field stimulation (2 to 32 Hz) and also to noradrenaline. This prostaglandin had quantitatively similar effects on the responses to both types of stimulus. 4 PGD2 was without effect on the inhibitory responses evoked by field stimulation in the presence of guanethidine. PGF2 alpha seemed to reduce the inhibitory responses to low frequencies of stimulation (0.5 to 1.5 Hz), but this effect was marginal. 5 The results suggest that PGD2 facilitates sympathetic neurotransmission in this tissue by both pre- and post-junctional actions. The effect of PGF2 alpha seems likely to be mediated predominantly post-junctionally.