Methione-enkaphine (Met-Enk), an opioid pentapeptide with awide distribution in the central nervous system and peripheral tissue, was studied its effects on proinflamamtory cytokines, such as, interleukin-I (IL-1) and tumor necrosis factor-α(TNF-α) and nitric oxide (NO) which are involved in various physiopathological conditions in the CNS on rat microglia cultures. The biological activities of IL-1, TNF-α was tested by mouse thymocyte proliferation and L929 cytotoxity assay.NO levels were represented as nitrite concentration which is determined Methione-enkaphine (Met-Enk), an opioid pentapeptide with a wide distribution in the central nervous system and peripheral tissue, was studied its effects on proinflamamtory cytokines, such as, interleukin-I (IL- 1) and tumor necrosis factor-a TNF-α) and nitric oxide (NO) which are involved in various physiopathological conditions in the CNS on rat microglia cultures. The biological activities of IL-1, TNF-α was tested by mouse thymocyte proliferation and L929 cytotoxity assay. NO levels were represented as nitrite concentration which is determined