title: Anxiolytic-like effect induced by chronic stress is reversed by naloxone pretreatment.
abstract: The present study assesses the influence of different restraint schedules on behavioral parameters determined by a conflict test, namely the light-dark transitions (LDT) as well as the opiate modulation on the behavioral consequences induced by chronic restraint. Finally, another group of animals that received naloxone (NAL) and/or chronic stress was either exposed to a single foot shock session or administered a single dose of the beta-carboline FG 7142 (N'-methyl-beta-carboline-3-carboxamide) immediately prior to the LDT test. We observed that a single restraint session (2 h) induced a decrease of LDT and time spent in the lit box, while chronic restraint (2 h per day for up to 7 days) induced a significant increase in both parameters. However, this increasing effect was blocked by a NAL administration (2 mg/kg IP) prior to each of the seven restraint events. A single foot shock or FG administration produced a clear anxiogenic response, an effect that was absent in animals previously submitted to chronic stress. In addition, NAL pretreatment abolished the chronic stress-induced attenuating effect on the behavioral suppression induced after either foot shock or FG administration. Therefore, these findings demonstrate that a previous history of chronic stress, leading to adaptation, induced an anxiolytic-like effect, and attenuated the behavioral suppression produced by acute stressors. There seems to be an endogenous opiate mechanism involved in the behavioral influence induced by chronic stress.
authors.affiliation: Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
authors.forename: L M
authors.initials: LM
authors.lastname: Cancela
authors.forename: C
authors.initials: C
authors.lastname: Bregonzio
authors.forename: V A
authors.initials: VA
authors.lastname: Molina
mesh_terms: D000223:Adaptation, Psychological; D000704:Analysis of Variance; D000818:Animals; D001008:Anxiety Disorders / Q000188:drug therapy* / Q000209:etiology; D002908:Chronic Disease; D003220:Conflict, Psychological; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012149:Restraint, Physical; D013312:Stress, Physiological / Q000150:complications*
chemical_list: D009270:Naloxone