Current antipsychotics cause hyperprolactinemia by D2 receptor antagonism in the pituitary gland, and EPS such as Parkinsonism probably due to excessive activation of the indirect pathway.9, 36, 37 The combined effects of TAK‐063 and either haloperidol or olanzapine on plasma prolactin levels and potential for inducing Parkinsonism were evaluated in rats. The gene discussed is PRL; the disease is hyperprolactinemia.