Different dopaminergic mechanisms for amfonelic acid, amphetamine and apomorphine.

Rats were trained to discriminate between the stimulus properties of intraperitoneal 0.16 mg/kg apomorphine and saline in a two-lever, food-motivated operant task. Employing the selected lever and the extended schedule performance measurements to indicate the generalization effect and perseverance of that effect, respectively, neither d-amphetamine nor amfonelic acid produced apomorphine-like discriminative properties. In contrast, administration of 0.1 or 0.2 mg/kg n-propylnoraporphine was observed to produce responses and perseverance on the apomorphine-appropriate lever that was similar to that seen after 0.16 mg/kg administration. The results of this behavioral experimentation are consistent with the notion that d-amphetamine, amfonelic acid and apomorphine may produce their dopaminergic effects by different mechanisms of action and the possibility of two sites of action for n-propylnoraporphine is discussed.