Striatal dopamine receptor sensitivity after subchronic fencamfamine in the rat.

Dopamine (DA) receptor sensitivity was assessed in the rat striatal system following subchronic treatment with fencamfamine or saline for 7 days (10 mg/kg i.p.). Seventy-two hours after the last injection the stereotyped behaviour and general activity induced by apomorphine or saline were evaluated. Apomorphine (2.0 mg/kg s.c.) induced a decrease of the stereotypic response when fencamfamine-pretreated animals were compared to saline-treated ones while apomorphine (0.02 mg/kg s.c.) failed to alter the general activity of animals, treated with fencamfamine or not. In biochemical experiments subchronic fencamfamine did not alter the effects of apomorphine (0.02 mg/kg s.c.) in reducing homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) striatal levels, when compared to saline. In addition we observed a slight but significant reduction in the total dopamine receptor content in the striatum labelled by [3H]spiroperidol. These findings indicate that subchronic fencamfamine treatment leads to a desensitization of postsynaptic DA receptors in rat striatum.