betah-endorphin: antidiuretic effects in rats.

Human beta-endorphin (betah-EP) inhibits urine flow in rats. This antidiuretic effect of the peptide occurs after intravenous and intraventricular injections. Intravenously, betah-EP is 24 times more potent than morphine. Intraventricularly, betah-EP is 24 times more potent than morphine. Intraventricularly, betah-EP is effective at doses (0.45 microgram) which have no antidiuretic activity when injected intravenously. This fact suggests that one site of the antidiuretic action of betah-endorphin may be in the central nervous system. Animals tolerant to morphine are also tolerant to the antidiuretic effects of betah-endorphin.