Impact of social factors on stress-produced responses and cocaine memory

Abstract

Social factors play an important role in stress responses and drug abuse Our previous report indicated that presence of male conspecifics throughout a stress procedure reversed the stress-induced decreases in dentate gyrus (DG) neurogenesis in male mice These findings imply that 1) mouse DG neurogenesis is susceptible to stress and 2) presence of conspecifics can be used as an effective way of social support to attenuate certain stress-induced responses in mice It was of interest to note that adult male and female animals exhibited differential degree of DG neurogenesis Moreover stress susceptibility and the prevalence of certain emotion disorders were variant in two sexes This study was divided into two parts First part was undertaken to assess sex differences and the modulating effects of gonad intactness and the estrous phase on basal and the stressor-decreased cell proliferation and early differentiation in Balb/C mouse dentate gyrus (DG) Besides we compared the stress-reversing effects exerted by the presence of male and female Balb/C mouse odors in stressed male and female mouse DG in this regard A number of social factors have been known to affect drug use and the development of drug dependence Second part was undertaken to study whether the presence of a companion group may affect cocaine-produced hedonic effect by using cocaine-induced conditioned place preference (CPP) in a mouse model Three male conspecific cocaine-free or -treated mice in together served as a conspecific mice served as a companion group in this study In the first part the results indicated that sexual differences in baselines in the number of newly proliferative cells neuroblasts and the sensitivity to stress-altered neuronal lineage commitment in the DG could be in part due to gonadal hormone differences between the two sexes Mouse odors may reverse stressor-decreased newly proliferative cells and neuroblasts in male but not in female mouse DG by restoring BDNF and NGF levels In the second part the results indicated that the presence of companions may attenuate cocaine-produced CPP possibly by decreasing cocaine-stimulated dopamine release in the nucleus accumbens

Date of Award	2014 Jul 25
Original language	English
Supervisor	Lung Yu (Supervisor)