Effects of beta-endorphin on norepinephrine release in hypertension.

Recent studies have suggested an involvement of the endogenous opioid system in blood pressure control. The purpose of the present study was to determine the role of beta-endorphin in the regulation of sympathetic nervous activity in the central nervous system of hypertension. The effects of beta-endorphin on the electrically evoked release of [3H]norepinephrine (NE) were investigated in superfused slices of rat medulla oblongata. Beta-endorphin inhibited the stimulation-evoked NE release in a dose-dependent manner in rat medulla oblongata. In the medulla oblongata of spontaneously hypertensive rats (SHR), the inhibitory effect of beta-endorphin on the stimulation-evoked NE release was significantly smaller than in the medulla oblongata of Wistar-Kyoto rats. These results showed that beta-endorphin might reduce NE release in rat medulla oblongata. Furthermore, the lesser inhibitory effect of beta-endorphin on NE release in SHR might suggest that the opioid peptide could be involved in the regulation of central sympathetic nervous activity in hypertension.