Last, to trigger endogenously sourced hypersecretion of Prl, virgin male rats received an i.p. injection of the dopamine D2 receptor-blocking antipsychotic haloperidol (Banasikowski and Beninger, 2012; Hillegaart and Ahlenius, 1987) or eticlopride (Svenningsson et al., 2000; Tang and Dani, 2009), a selective D2-type receptor antagonist, known to induce hyperprolactinemia in research models and in the clinic (Spitzer et al., 1998; Arita and Kimura, 1986; Morgan et al., 1984). This evidence concerns the gene DRD2 and hyperprolactinemia.