Behavioral and neurochemical effects induced by subchronic l-deprenyl administration

(-)Deprenyl was administered orally to rats for 15 days. In the staircase maze, a reduction of incorrect responses was observed at 0.9 mg/kg/day; higher or lower doses (3.5 or 0.35 mg/kg/day) were ineffective. In the same range of doses, the subchronic administration of (-)deprenyl did not modify the levels of norepinephrine, 5-hydroxytryptamine, 5-hydroxyindolacetic acid or the density and affinity of alpha-noradrenergic receptors in the cortex, olfactory system, hippocampus and striatum. An increase of the dopamine and a reduction of dihydroxyphenylacetic acid levels was observed only at the highest tested doses, at which no behavioral modification was observed. Only at 1.0 mg/kg/day did (-)deprenyl increase the acetylcholine (ACh) levels in the olfactory system, hippocampus and striatum. This neurochemical effect may be correlated to the behavioral effect observed in the same range of doses. We propose that this increase of ACh levels is determined by an activation of dopaminergic systems, resulting from the increase in the levels of PE caused by the inhibition of monoamine oxidase B (MAO-B) by (-)deprenyl.