ENDOMORPHINS HAVE OREXIGENIC AND ANXIOLYTIC ACTIVITIES IN MICE

THIS study was designed to investigate the effects of endomorphin 1 an d 2, recently identified mu-opioid receptor selective peptides, on foo d intake and anxiety in non-food-deprived mice. The intracerebroventri cular (i.c.v.) injection of either endomorphin 1 or 2 (0.03-30 nmol) i ncreased food intake in a dose-related manner. A significant increase was observed 20 min after i.c.v. injection of endomorphin 1 dr 2 and c ontinued for 4 h. In the elevated plus maze test, the i.c.v. injection of endomorphin 1 (30 nmol) significantly decreased the normal prefere nce for the closed arms. These results suggest that endomorphin produc es orexigenic and anxiolytic effects, and that the mu-opioid receptor contributes to the regulation of feeding and anxiety in mice. Neuro Re port 9: 2265-2267 (C) 1998 Rapid Science Ltd.