The comparative roles of dopaminergic and serotonergic mechanisms in mediating quipazine induced increases in locomotor acitivity

The effect of dopaminergic and serotonergic agonists and antagonists on quipazine induced locomotor activity was investigated in rats. Though quipazine is generally considered to be a relatively pure serotonergic agonist, its effects on locomotor activity were inhibited by small doses of a centrally acting DA receptor blocking agent (haloperidol), while three different serotonergic (5-HT) antagonists were without effect on this behavior. Moreover, quipazine induced locomotor activity was markedly inhibited by the 5-HT substrate 5-hydroxytryptophan. The data suggest that quipazine induced locomotor activity primarily involves dopaminergic mechanisms, with 5-HT playing either no role in stimulating this behavior, or a subsidiary one, requiring intact central dopaminergic receptors for its expression.