Effect of chronic variable stress on central regulation of food intake and neurogenesis
Résumé
Chronic stress alters several central mechanisms including those of food intake regulation and neurogenesis. Our goal was to deter-mine the effect of chronic variable stress (CVS) on these two systems. Two experiments were performed using 2 weeks CVS in male Wistar rats. CVS consisted of daily unpredictable exposure to a variety of stressors. In the first experiment, food intake and body weight were measured daily. At the end of CVS, hypothalamic neuropeptide mRNA expression, basal plasma hormone levels and body composition were measured. In the second experiment, the effects of CVS on brain morphology were assessed by MRI, and at the cellular level by staining. Rats exposed to CVS displayed greater corticotropin releasing factor (CRF) and a tendency towards lower neuropeptide Y (NPY) expression, plus a decreased body weight due to diminution of adipose tissue mass compared to control rats. A decrease in food intake only partly explained this decrease since stressed rats also showed a reduced weight gain per kJ ingested. Stressed rats had a 2-fold increase in basal corticosterone levels. The effects of CVS on neuroanatomy of the brain are currently being analysed. In conclusion, CVS affected central food intake regulation. CVS induced a decrease in food intake, probably due to CRF inhibition of orexigenic NPY neurons. The lowered body weight of stressed rats could be explained by an inhibition of food intake and, since CVS only lasted 2 weeks, an acute lipolytic effect of corticosterone.