Modulation of autonomic neurotransmission by PGD2: comparison with effects of other prostaglandins in anesthetized cats.

Experiments with anesthetized cats were done to study possible roles of different prostaglandins (PGs) in modulating sympathetic neuroeffector transmission. We recorded contractions of the nictitating membrane (n.m.), blood flow in the carotid artery, heart rate and blood pressure, both under control conditions and while stimulating the cut cervical sympathetic nerve. Intra-carotid arterial injection (i.a.) of PGD2 depressed sympathetic transmission to the n.m. without depressing the effects of exogenous norepinephrine (NE). In contrast, PGE2 enhanced the effects of nerve transmission or exogenous NE on the stimulated n.m. PGI2 had similar but shorter effects to PGE2. PGF2 alpha or a stable PGH2 analog, contracted the n.m. smooth muscle with no detected effect on nerve transmission. Carotid blood flow was increased by PGD2, PGE2 and PGI2. PGD2 and PGI2 caused bradycardia that could be blocked by atropine. This ability of PGD2 to modulate autonomic nerve activity is of particular interest because of recent reports that nerve tissue synthesizes PGD2.