THE EFFECT OF L-DEPRENYL ON BEHAVIOR, COGNITIVE FUNCTION, AND BIOGENIC-AMINES IN THE DOG

Behavioral and pharmacological effects of oral administration of L-dep renyl in the dog are described. Spontaneous behavior is unaffected at doses below 3 mg/kg while at higher doses there was stereotypical resp onding. There was evidence of improved cognitive function in animals c hronically treated with a 1 mg/kg dose but the effectiveness varied co nsiderably between subjects. Chronic administration produced a dose de pendent inhibition in brain, kidney and liver monoamine oxidase B, and had no effect on monoamine oxidase A. There were also dose dependent increases in brain phenylethylamine and in plasma levels of amphetamin e. Dog platelets did not have significant levels of MAO-B. Brain dopam ine and serotonin metabolism were unaffected by L-deprenyl at doses up to 1 mg/kg. It appears that for the dog, deamination of catecholamine s is controlled by MAO-A. Nevertheless, it is suggested that L-depreny l serves as a dopaminergic agonist, and there is also evidence that it affects adrenergic transmission. These catecholaminergic actions may account for the effects Of L-deprenyl on behavior and cognitive functi on.