Neuropeptide Glutamic acid-Isoleucine (NEI) is processed from pre-pro melanin concentrating hormone (ppMCH).In males,the localization of NEI is almost identical to that of MCH,the cell bodies of both being located primary in the lateral hypothalamic area and zona incerta,projecting fibers throughout the brain.Although MCH has been widely studied,the role that NEI plays in the brain circuitry is poorly investigated.Recently we showed that intracerebroventricular (icv) injection of NEI increases serum lutienizing hormone (LH) levels In order to identify the anatomical substrate underlying this effect,we used combined immunohistochemistry methods to analyze the forebrains of females on the diestrus and proestrus days,as well as those of ovariectomized females treated with estradiol benzoate,with estradiol benzoate plus progesterone or with sesame oil (control animals).