Intracerebroventricular met-enkephalin administration modulates adjuvant arthritis

The purpose of this study was to investigate the anti-inflammatory properti es of intracerebroventricular met-enkephalin (met-enk) administration in an animal model of arthritis. Adjuvant arthritis was induced in rats by intra dermal inoculation of mycobacterium butyricum and the effects of intraventr icular met-enk+thiorphan (enkephalinase inhibitor) were studied. Treatment was initiated either simultaneously with the bacterial inoculation (prevent ive group) or on post-inoculation day 17 after the appearance of inflammati on (treatment group). The degree of inflammation was evaluated by measuring the diameter and the circumference of the ankle joint immediately before t he sacrifice (day 31) and by histologic examination of ankle joint sections . The results of this study revealed that combined intraventricular injecti ons of met-enk+thiorphan reduced the arthritic-like inflammation in the pre ventive group as well as in the treatment group. These findings suggest tha t centrally applied met-enk+thiorphan may suppress the development adjuvant arthritis as well as the symptoms of manifest arthritis. Thus central met- enk may be involved in both hypothalamic pituitary adrenal axis and immune forms of stress-induced modulation. (C) 2000 Elsevier Science B.V. All righ ts reserved.