Cardiovascular and antidiuretic effects of central prostaglandin E2.

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Abstract
Unanesthetized normal and water-loaded rats were tested for cardiovascular and antidiuretic responses to intracerebroventricular (I.V.T.) injections of prostaglandin E2 (PGF2). I.V.T. injections of PGE2 produced tachycardia and a slow rise in blood pressure that reached a peak in 15 min and lasted up to 2 h. I.v. pre-treatment with phenoxybenzamine, an .alpha.-adrenergic blocker, inhibited pressor but not heart rate responses to I.V.T. PGF2. Pre-treatment with propranalol, a .beta.-adrenergic blocker, inhibited tachycardia but not pressor responses to I.V.T. PGE2. Atropine attenuated heart rate and blood pressure responses when higher doses of PGE2 were tested. In water-loaded rats, I.V.T. PGE2 produced antidiuretic effects suggesting release of antidiuretic hormone in subpressor amounts. Antidiuretic but not cardiovascular responses to I.V.T. PGE2 were abolished by median eminence lesions. I.v. PGF2 infusion produced a decrease in blood pressure and no antidiuretic effects, indicating that both responses were centrally mediated. I.V.T. PGE2 produces pressor and tachycardia responses in the unanesthetized rat which are mediated primarily by centrally mediated sympathetic outflow.