beta-Endorphin: possible involvement in the antihypertensive effect of central alpha-receptor activation.

Clonidine and L-alpha-methylnoradrenaline (but not D-alpha-methylnoradrenaline) increase the release of a substance with beta-endorphin immunoreactivity from slices of brainstem of spontaneously hypertensive rats, but not that of normotensive rats. It was reported earlier that opiate antagonists inhibit the hypotensive action of clonidine and alpha-methyldopa in spontaneously hypertensive but not in normotensive rats and that beta-endorphin has hypotensive effects of its own. Together, these findings indicate that release of beta-endorphin by central alpha-receptor agonists may contribute to the antihypertensive action of these drugs.