FACILITATION OF SYMPATHETIC NEUROTRANSMISSION IN THE RAT ANOCOCCYGEUS MUSCLE BY PROSTAGLANDINS D2 AND F2α

Abstract

1 Investigations were made into the effects of prostaglandins D₂ (PGD₂) and F_2α (PGF_2α) 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 × 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 PGF_2α (2.8 × 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. PGF_2α 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 PGF_2α seems likely to be mediated predominantly post-junctionally.