The role of brain norepinephrine in the anorexic effects of dextroamphetamine and monoamine oxidase inhibitors in the rat

The effects of d-amphetamine on food and water intake and brain monoamine concentrations in rats that had been deprived of food and water for 24 h were compared with those of two MAO inhibitors: tranylcypromine which has prominent amphetamine-like activity; and, pargyline which does not. All drugs produced dose-related depressions of food and water intake. The anorexic effects of the MAO inhibitors were correlated, over a 16-fold dose range, with elevated levels of norepinephrine, dopamine and serotonin. The anorexic effect of d-amphetamine was blocked by -methyltyrosine, an inhibitor of catecholamine synthesis. -Methyltyrosine failed to block the depression of food and water intake caused by the MAO inhibitors, although the rise in catecholamine levels was prevented. It was concluded that the mechanisms by which d-amphetamine produces anorexia may differ from those of the MAO inhibitors. Central adrenergic mediation appears to play a role in the anorexic activity of d-amphetamine, but may not be essential for the anorexic effect of tranylcypromine and pargyline.Publication No. 1023 of the Division of Basic Health Sciences of Emory University. This investigation was suported by NIMH Grant MH 12870-03.Postdoctoral trainee of NIH Graduate Pharmacology Training Grant GM-179 during part of this work.