The effect of repeated administration of (-) deprenyl on the phenylethylamine-induced stereotypy in rats.

Phenylethylamine (PEA) in a dose of 40 mg/kg induces a moderate and short-lasting stereotype behaviour. The intensity and duration of PEA-induced stereotypy was strongly potentiated in rats with single selective doses of (-) deprenyl and J-508 (0.25 and 0.1 mg/kg s.c., respectively), which inhibit selectively the B form of MAO. Neither the increase of the single dose nor the daily administration of the selective doses of (-) deprenyl and J-508 for eight weeks caused a more intense or longer lasting potentiation of the PEA effect than single small dose of these drugs. Stopping administration of MAO-B inhibitors, normal sensitivity towards PEA returned after 3-4 weeks, in a parallel way with the recovery of MAO-B activity in the brain. Clorgyline, the selective inhibitor of MAO-A failed to influence the effect of PEA (0.25-2 mg/kg s.c.). The data support the view that the strong potentiation of the stimulatory effects of endogenous PEA via inhibition of its metabolism by (-) deprenyl may play a role in the antidepressant effect of this drug in man.