Poster Presentation The International Congress of Neuroendocrinology 2014

Changes in the hippocampal nitrergic system during short term restraint stress (#373)

Hsiao-Jou Chen 1 , Jereme G Spiers 1 , Conrad Sernia 1 , Nickolas A Lavidis 1
  1. The University of Queensland, St. Lucia, QLD, Australia

Stress accelerates cellular metabolism producing an increase in free radicals such as reactive oxygen and nitrogen species. Chronic overproduction of these reactive nitrogen species has been implicated in the aetiology of depressive-like behaviour. However, the time course and extent of nitrosative changes in stress-related brain regions during acute stress has not been characterised. In this study, outbred male Wistar rats aged 6-7 weeks postnatal were randomly allocated into control, 60 or 120 minute restraint stress groups (n=8/group). A blood sample was collected via cardiac puncture at the end of each stress treatment and plasma was stored for later determination of corticosterone. Brain regions of interest were cryo-dissected and stored at -80oC prior to assaying for nitric oxide production, nitric oxide metabolism, and relative gene expression of neuronal nitric oxide synthase. Corticosterone concentrations increased by approximately 150% at 60 (p<0.001) and 100% at 120 (p<0.001) minutes from baseline indicating effective stress exposure. Hippocampal glucocorticoid receptor mRNA levels were significantly downregulated by 15% at 60 (p<0.05) and 20% at 120 (p<0.01) minutes consistent with intact glucocorticoid negative feedback. The production of nitric oxide in the hippocampus was increased by approximately 20% to 25% at 60 and 120 (p<0.05) minutes of stress. Nitric oxide metabolism, measured as stable metabolites nitrite and nitrate, demonstrated a stress-induced increase of 65% at 60 (p<0.01) and 50% increase at 120 (p<0.05) minutes. Interestingly, neuronal nitric oxide synthase mRNA expression was approximately 15% lower at 60 and 120 (p<0.05) minutes of stress. No significant changes in the expression of neuronal nitric oxide synthase, nitric oxide production and metabolism were observed in the striatum. It was concluded that a single episode of short term stress induces rapid changes of the nitrergic system in the hippocampus and these demonstrate a degree of regional specificity.