Involvement of Cholecystokininergic Systems in Anxiety-Induced Hyperalgesia in Male Rats: Behavioral and Biochemical Studies

Abstract
Keeping in mind the increased pain complaints reported in anxious or depressive patients, our goal was to investigate in rats the consequences of an experimentally provoked state of anxiety/depression on pain behavior and on its underlying mechanisms. We therefore used a model of social defeat consisting of a 30 min protected confrontation followed by a 15 min physical confrontation, repeated during 4 d, that elicited symptoms close to those observed in humans with anxiety or depression. Indeed, 5 d later, animals subjected to social-defeat confrontation were characterized by a decrease of sweet-water consumption and of body weight, and a hyperactivity of the hypothalamic–pituitary–adrenal axis, suggesting that the social-defeat procedure induced a prolonged state of anxiety.