Analysis of the mechanism of d-amphetamine-and apomorphine-induced changes of ascorbic acid catabolism in discrete brain areas of the rat

Ascorbic acid (AA) levels and dehydroascorbic acid/ascorbic acid (DHAA/AA) ratios were determined in hypothalamus, striatum, and remaining brain of male Wistar rats, after single or repeated injections of d-amphetamine (1.8 mg/kg/day s.c.), apomorphine (1.0 mg/kg/day s.c.), and/or haloperidol (0.1 mg/kg/day i.p.). Major changes were observed in hypothalamus, in which all drugs significantly increased DHAA/AA ratio. Apomorphine and haloperidol consistently decreased AA level as well. The DHAA/AA ratio increase was observed also when apomorphine and d-amphetamine were associated with haloperidol. In striatum, apomorphine (single) and d-amphetamine (repeated) injections increased DHAA/AA ratios; such AA oxidation increase was inhibited by haloperidol; the increases (d-amphetamine) or decrease (apomorphine) of AA levels were also inhibited by haloperidol; haloperidol alone did not modify DHAA/AA ratio and induced minor changes of striatal AA level. In remaining brain, apomorphine (single) and d-amphetamine (repeated) treatment increased DHAA/AA ratio; such increase was observed also when haloperidol was associated with apomorphine or d-amphetamine; moreover, haloperidol by itself increased AA oxidation, although to a lesser extent than it did in hypothalamus. It is concluded that AA catabolism can be activated in the rat striatum by a dopaminergic mechanism; in hypothalamus and in remaining brain, the AA catabolism activation appears rather to be a non-specific effect of the pharmacological manipulation.