The effect of prostaglandin E2 microinjected into the rat hypothalamus on urinary excretion of water and sodium.

1 Effects of prostaglandin E2 (PGE2) microinjected into the supraoptic (SON) and the ventromedial nuclei of the hypothalamus (VMH) on urine outflow were studied in rats anaesthetized with ethanol. 2 PGE2 injected into the SON caused antidiuresis and increased the excretion rate of Na+. These effects of PGE2 were prevented by pretreatment with phentolamine but not propranolol, suggesting that they are mediated by alpha-adrenoceptors in the SON. 3 PGE2 injected into the VMH caused diuresis and increased the excretion rate of Na+. These effects were prevented by pretreatment with propranolol but not phentolamine, suggesting that they are mediated through beta-adrenoceptors in the VMH.