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...high levels of stress have deleterious effects on hippocampal functioning while simultaneously potentiating amygdala functioning (Elzinga & Bremner, 2002; Metcalfe & Jacobs, 1998; Payne et al., 2006; =-=Vyas, Mitra, Rao, & Chattarji, 2002-=-). Theoretically, this should produce strong S-reps but weaker or impoverished C-reps. In the revised dual representation model, we suggest accordingly that flashbacks in PTSD result from the creation...

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...y, dehydrated in absolute alcohol, cleared in xylene and overslipped. Slides were coded prior to quantitative analysis. The xperimenter was blind to the code, which was broken only after he morphological analysis was completed. nalysis of dendritic spine density ur analysis of MeA neurons was restricted to those located etween Bregma: 2.3 mm and 3.2 mm. To be selected for orphological analysis, Golgi-impregnated neurons had to satisfy he following criteria that have been applied in similar morphometic analyses in earlier reports in the literature (Watanabe et al., 992; Conrad et al., 1999; Vyas et al., 2002; Mitra et al., 2005): (1) tresence of untruncated dendrites, (2) consistent and dark imregnation along the entire extent of all dendrites, and (3) relative solation from neighboring impregnated neurons to avoid interferng with analysis (e.g. avoid extensive dendritic overlap). Using hese criteria in the MeA, we analyzed medium spiny stellate neurons ecause in earlier anatomical studies (reviewed in McDonald, 1992) his class of neurons was the most predominant cell type in the eA. Further, these MeA neurons analyzed were selected ranomly without any bias and the first six neurons in a given br...

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...midal neurons, decreases hippocampal neurogenesis, and decreases hippocampal glucocorticoid receptor mRNA expression (Fuchs & Gould, 2000; Magarinos & McEwen, 1995; Pham, Nacher, Hof, & McEwen, 2003; =-=Vyas, Mitra, Rao, & Chattarji, 2002-=-). If high CORT levels persist for several weeks or months, hippocampal neurons are permanently lost (Sapolsky, 2000), but after shorter exposures, the damage appears to be reversible (Conrad, Magarin...

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...cEwen and Chattarji, 2004). The hippocampus, a main structure for spatial learning and memory, is susceptible to stress, and glucocorticoid damage produces dendritic remodeling of CA3quiatría, Facultad de Med 56 2 665 1951. Dagnino-Subiabre). er B.V. All rights reservedpyramidal neurons and a decrease in adult neurogenesis in the dentate gyrus (Sapolsky et al., 1991; Magariños and McEwen, 1995; McEwen, 1999). More recently, it has been shown that in addition to the hippocampus, the amygdala and prefrontal cortex are morphologically affected by stress and corticosterone in rats (Wellman, 2001; Vyas et al., 2002; Radley et al., 2004). These alterations are related to learning, memory,icina, Pontificia Universidad Católica de Chile, Ave. Marcoleta 387, . Fig. 1 – Effect of chronic immobilization stress on spontaneous motor responses in rats. Stress does not affect the motor activity of the experimental animals. Bars represent the total spontaneous motor activity in a 30-min observation period. The values are the mean ± SEM. 28 B R A I N R E S E A R C H 1 0 8 6 ( 2 0 0 6 ) 2 7 – 3 4and emotional response impairments (McEwen and Chattarji, 2004). In humans, postmortem and brain imaging studies have reve...

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...phy of the dendritic arborization in the BLA and extended amygdala, accompanied by dendritic atrophy and decreases in spine density in medial prefrontal areas and the hippocampus (Mitra et al., 2005; =-=Vyas et al., 2002-=-). In rats, these changes are associated with standard behavioral indicators of anxiety in rodents, including decreased time spent in the open (exposed) arms of an elevated plus maze and reduction in ...

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... stress induces dendritic atrophy and debranching in hippocampal neurons, it enhances dendritic arborization and synaptic connectivity in the amygdala (Mitra, Jadhav, McEwen, Vyas, & Chattarji, 2005; =-=Vyas, Mitra, Rao, & Chattarji, 2002-=-). Interestingly, the amygdala has been assigned a critical role in acute stress effects on memory functions (Kim et al., 2001; Roozendaal, 2002) and in the ‘‘emotional” modulation of spatial and S-R ...

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...us granule neurons, and impairs hippocampal-dependent cognitive functions (McEwen, 1999; Joels et al., 2007). High levels of corticosterone or chronic stress also impair long-term potentiation (LTP) and facilitate long-term depression (LTD) induced by electrical stimulation in hippocampus (Kim and Diamond, 2002; Alfarez et al., 2003). On the other hand, chronic stress has been shown to enhance amygdala-dependent fear conditioning (Conrad et al., 1999) and anxiety-like behavior (Mitra et al., 2005), which may be correlated to the stress-induced dendritic growthand spinogenesis in this region (Vyas et al., 2002; Mitra et al., 2005). In this study, we have demonstrated that glutamatergic transmission in PFC pyramidal neurons is significantly suppressed in young male rats exposed to repeated stress, without the apparent loss of synapses. In contrast, no such effect is observed in striatal medium spiny neurons or CA1 pyramidal neurons, consistent with the lack of effect of chronic stress on synaptic currents in hippocampal dentate gyrus neurons (Karst and Joels, 2003). It suggests that PFC is a more sensitive area in response to repeated stress, especially during the adolescent period when this region...

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... to stressful events early in life had increased amygdala and medial prefrontal gray matter volumes and displayed elevated anxiety. Chronic stress enhances dendritic arborization in the rat amygdala (=-=Vyas et al., 2002-=-), a process clearly reflecting synaptic plasticity and enlarged amygdala volumes have been reported in anxiety disorder patients (e.g., Juranek et al., 2006). Hippocampal activations appear related t...

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...urons (32,s33). Chronic exposure to high physiological levels of corticosterone in mice is sufficient tosproduce anxiety-like behavior and also result in dendritic hypertrophy in basolateral amygdalas=-=(27, 44)-=-. Amygdala also provides positive feedback regulation to the HPA axis (27). We havesnoticed unaltered GR levels in the amygdala of Ube3a-maternal deficient mice brain. Thissindicates amygdala in these...