The effect of repeated treatment with brofaromine, moclobemide and deprenyl on alpha 1-adrenergic and dopaminergic receptors in the rat brain.

The binding of [3H]prazosin to alpha 1-adrenoreceptors, as well as of [3H]SCH 23390 (R(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-o l) to dopamine D1 receptors, and [3H]spiperone to D2 receptors was studied following repeated administration of the monoamine oxidase inhibitors (MAOI) brofaromine, moclobemide and deprenyl to rats. Scatchard analysis showed no change in the density (Bmax) and affinity (Kd) of [3H]prazosin sites, yet the ability of phenylephrine (an alpha 1-adrenoceptor agonist) to compete for [3H]antagonist binding sites was enhanced in the cerebral cortex after repeated brofaromine administration, as well as in the hippocampus of rats pretreated with moclobemide and deprenyl. The density and the binding affinity of dopaminergic D1 and D2 receptors were not affected by repeated treatment with all the MAOI used. The results seem to indicate that a small increase in the alpha 1-adrenoceptor agonist affinity occurs after repeated administration of MAOI.