Antimanic-like effect of tamoxifen is not reproduced by acute or chronic administration of medroxyprogesterone or clomiphene

► Tamoxifen, a PKC inhibitor and antiestrogenic drug, blocked methylphenidate-induced hyperlocomotion. ► Medroxyprogesterone and clomiphene, antiestrogenic drugs, did not block methylphenidate-induced hyperlocomotion. ► These results indicated that the antimanic-like effect of tamoxifen is related to its PKC activity.