Dopamine reuptake inhibitors and dopamine releasers : differential effect on plasma prolactin in the rat

Administration of diclofensine (5, 10 and 20 mg/kg ip) and CDCI (25 and 50 mg/kg ip), two potent inhibitors of dopamine (DA) reuptake, with virtually no DA releasing activity at the doses used, failed to alter either baseline plasma prolactin (PRL) or anterior pituitary DA concentrations in unanesthetized male rats. In contrast, nomifensine (5 and 10 mg/kg ip), a drug which induces both DA release and blockade of DA reuptake, lowered plasma PRL levels and increased anterior pituitary DA concentrations. The same effects were shared by diclofensine when administered at doses (45 and 100 mg/kg ip), reportedly capable of also affecting DA release. These data indicate that DA recapture into tuberoinflundibular DA nerve terminals does not play a major role in the removal of DA released into the hypophyseal portal system and that this mechanism is not operative in the inhibitory control of DA over PRL secretion.