6-methoxy-tetrahydro-beta-carboline (pinoline): effects on plasma renin activity and aldosterone, TSH, LH and beta-endorphin levels in rats.

Plasma renin activity and the plasma concentrations of aldosterone, TSH, LH and beta-endorphin were radioimmunologically determined in rats after ip administration of 15 mg/kg of 6-methoxy-tetrahydro-beta-carboline (6-MeO-THBC, pinoline), a compound found to occur normally in mammalian and avian pineal gland. A 2.6-fold increase of plasma aldosterone concentration was found and it was preceded by increase of plasma renin activity. An increase was also found in beta-endorphin/beta-lipotrophin concentration while TSH and LH concentrations did not change significantly. The present results do not prove nor exclude the concept that 6-MeO-THBC is the 'adrenoglomerulotropin'. The effects of 6-MeO-THBC on plasma beta-endorphin/beta-lipotrophin levels may be mediated by the dopaminergic or 5-HT-neurones.