The purpose of the present study was to determine the effects of quinelorane, a selective D2 receptor agonist, on concentrations of prolactin and alpha-melanocyte-stimulating hormone (alpha-MSH) in plasma of male rats. Quinelorane decreased plasma concentrations of prolactin but not of alpha-MSH, whereas, the D2 receptor antagonist raclopride increased plasma concentrations of both hormones. Quinelorane reversed the effects of raclopride on circulating levels of prolactin, but not alpha-MSH. The results of this study suggest that secretion of hormones from melanotrophs and lactotrophs is regulated by different subtypes of D2 receptors.