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It is known that early-life stress events induce profound consequences on emotional brain regions including amygdala, involved in emotional processing and the ventral tegmental area (VTA), which contains neuron cell bodies of the mesolimbic dopaminergic system. The aim of this study is to test the hypothesis that stress induced by long-term social isolation from weaning in female rats is associated with alterations in amygdalar dopamine receptor gene expression and VTA dopamine concentrations. Rats were weaned on postnatal day 21 and then exposed to stress of chronic isolation for 9 weeks. Control animals were housed socially. Amygdalar dopamine D 1 but not D 2 receptor gene expression was decreased in isolated rats compared to controls. Dopamine concentrations in the VTA were enhanced following chronic isolation. A negative correlation was observed between amygdalar D 1 gene expression and dopamine concentrations in the VTA. In conclusion, a reduction of dopamine D 1 receptor gene expression in the amygdala in response to stress induced by chronic isolation in female rats was accompanied by an increase in dopamine concentration in the VTA. Further studies are needed to understand the physiological significance, if any, of negative association of amygdalar dopamine receptor D 1 gene expression and dopamine concentrations in the VTA.

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