The potentiating effect of clorgyline and pyrogallol on the blood pressure responses to norepinephrine.

Intraventricular administration of norepinephrine (NE) into pentobarbital anesthetized rats elicits a pressor or a depressor effect depending on the dose injected: after a low dose, a depressor response is seen while after a high dose, a pressor response is observed. In the animal pretreated intraventricularly with clorgyline or pyrogallol, the hypotensive effect of a low dose of NE was reversed to a hypertensive effect, while the hypertensive effect of a high dose of NE was markedly potentiated. This result suggests that brain monoamine oxidase and catechol-o-methyltransferase can metabolize centrally released NE before it leaks into the peripheral circulation.