The impact of the hormonal milieu and stress-associated hypothalamic dopaminergic activation on the rapid compensatory adrenal growth in cycling female rats.

OBJECTIVE We sought to investigate the impact of emotional and surgical stress applied in two hormonally different estrous-cycle phases as well as the hypothalamic dopaminergic involvement on the rapid compensatory adrenal growth (CAG) and the individual adrenal growth (IAG) in rats. DESIGN After surgery for left and sham adrenalectomy (Adx) carried out on either diestrus-2 (DE-2) or proestrus (PE), CAG and IAG were evaluated in PE or estrus (E), respectively. Hypothalamic dopaminergic activity was also assessed by measuring dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels in DE-2, PE and E in controls and in PE and E in sham and left adrenalectomized rats. All groups experienced similar chronic emotional stress assessed by the emotional reactivity score recorded during vaginal screening. RESULTS In controls, DOPAC levels in DE-2 were higher than in PE and E. In PE, following surgery in DE-2, DOPAC levels and DOPAC/DA ratio were increased compared to PE controls; CAG was not significant, while negative correlations of IAG and CAG with DOPAC/DA ratio were observed. In E, CAG and IAG were significant, while dopaminergic activity was not increased compared to E controls. CONCLUSIONS The significant CAG and IAG following left Adx in PE but not in DE-2 suggest a pronounced positive impact of the hormonal milieu on this process. The profound attenuation of CAG and IAG in PE suggests a negative effect of stress-associated dopaminergic activation.