Behavioural microanalysis of the role of dopamine in amphetamine anorexia.

A microstructural analysis paradigm was used to study amphetamine anorexia. Doses above 0.40 mg/kg significantly reduced food intake by reducing eating time; in contrast, eating rate was increased at these doses. Examination of the frequency distribution of interresponse times (IRTs) revealed a significant shift to shorter IRTs at doses as low as 0.125 mg/kg. Pimozide blocked amphetamine anorexia at 0.5 and 1.0 mg/kg, suggesting that at both doses amphetamine anorexia has a dopaminergic substrate. However, the atypical neuroleptic thioridazine did not antagonize amphetamine. Furthermore, effects of amphetamine were additive with those of apomorphine, administered at a dose known to suppress feeding by inhibiting mesolimbic DA neurons. These results provide evidence against an involvement of the mesolimbic DA system in amphetamine anorexia.