Orphanin FQ, a novel neuropeptide with anti-stress-like activity

Potential anxiolytic-like properties of intracerebroventricular (i.c.v.) in fusion of orphanin FQ (OFQ), a recently discovered neuropeptide, were inves tigated in the mouse defense test battery, a well-validated anxiolytic scre ening test. Zn this model, Swiss mice are directly confronted with a natura l threat (a rat) as well as situations associated with this threat. Primary measures taken during and after rat confrontation were flight, risk assess ment, defensive attack and escape attempts. Unlike the anxiolytic drug diaz epam (3-10 mu g/5 mu l, i.c.v.), which affected all defensive responses, OF Q (0.3-3 nM/5 mu l) only clearly reduced defensive upright postures and bit ing reactions. Subjects displayed these latter defensive behaviors upon for ced contact with the threat stimulus, a situation which is considered to be highly stressful. These results suggest that the OFQ system may not be pri marily involved in anxiety-related responses including cognitive aspects (i .e., risk assessment), while it may play a role in the adaptative responses to unavoidable or extreme stress stimuli. (C) 1999 Published by Elsevier S cience B.V. All rights reserved.