METABOLISM OF NOREPINEPHRINE RELEASED BY INDIRECTLY- ACTING SYMPATHOMIMETIC AMINES OR BY ADRENERGIC NERVE STIMULATION’

SMITH, CHARLES B.: The role of monoamine oxidase in the intraneuronal metabolism of norepinephrine released by indirectly-acting sympathomimetic amines or by adrenergic nerve stimulation. J. Pharmacol. 151: 207-220, 1966. Pretreatment of guinea pigs with a-methyldopa did not appreciably alter the effect of norepinephrine upon either the rate of isolated atria or the force of contraction of isolated left atrial strips. Pretreatment with pargyline, a monoamine oxidase inhibitor, slightly reduced the maximum response of the pacemaker to norepinephrine, but did not alter the effects of norepinephrine on force of contraction. 1-a-Methyl norepinephrine was found to be equipotent with norepinephrine on both rate and force of contraction. In contrast to the effects of norepinephrine, the effects of indirectly-acting sympathomimetic amines, tyramine, d-amphetamine and mephentermine, upon isolated atria and isolated left atrial strips were enhanced by pretreatment of guinea pigs with pargyline. Pretreatment with a-methyldopa enhanced the effects of all three indi-rectly-acting amines upon the rate of the pacemaker but not upon the force of contraction of the isolated left atrial strip. The response of the pacemaker to accelerans nerve stimu