The involvement of the sympathetic nervous system in the centrogenic pressor and tachycardiac effects of prostaglandins E2 and F2 alpha in anaesthetised cats.

The intracerebroventricular (i.c.v.) administration of prostaglandin E2 (PGE2, 1 micrograms) and prostaglandin F2 alpha (PGF2 alpha, 10 micrograms) produced prolonged pressor and tachycardiac responses in chloralose-anaesthetised cats. Phenoxybenzamine-pretreatment completely prevented the pressor response without altering the tachycardiac response, whereas propranolol intervention completely inhibited the tachycardiac response and also attenuated the pressor response. The pretreatment with pentolinium completely antagonised both the pressor and tachycardiac responses to i.c.v. PGE2 and PGF2 alpha. The results suggest that the centrally administered PGE2 and PGF2 alpha augment sympathetic outflow to the heart and vascular system and thereby cause excitatory cardiovascular responses in anaesthetised cats.