Early exposure to chronic variable stress facilitates the ocurrence of anhedonia and enhanced emotional reactions to novel stressors: reversal by naltrexone pretreatment.

ALEJANDRA ZURITA, ; GABRIEL CUADRA, ; I.D. MARTIJENA ; BRANDAO, M.L.; MOLINA VICTOR ALEJANDRO

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2000 vol. 117 p. 163 - 163

he present research studied the influence of an early chronic variable stress (CVS) paradigm - an animal model of depression - on behavioral responses to subsequent environmental challenges suggested to model anhedonia and emotional reactions such as anxiety and fear. In order to explore a potential involvement of an endogenous opiate mechanism - presumably activated during CVS exposure - in the development of such behavioral reactions, in all experiments rats were administered naltrexone (NAL, 2 mg/kg, i.p.) or vehicle (VH) prior to each daily stressor of the CVS procedure. Animals were exposed to CVS and 1 week later tested for sucrose preference (1%) in a free choice paradigm after the presentation or not of a 90-min restraint period. Only CVS treated animals that were later exposed to restraint showed a reduction of sucrose preference, this reduction was absent when CVS rats were pretreated previously with NAL. Moreover, CVS rats were one week later tested on the elevated plus maz