Conclusions
The decrease in circulating and brain levels of 3α,5α-THP may be due to alterations in the biosynthesis/metabolism or changes in the regulation of the HPA axis following FSS. Changes in GABAergic neuroactive steroids in response to stress likely mediate functional adaptations in neuronal activity. This may provide a potential targeted therapeutic avenue to address maladaptive stress responsivity.
Methods
Mice were exposed to FSS (10 min), and 50 min later, blood and brains were collected. Circulating pregnenolone and 3α,5α-THP levels were assessed in serum. Free-floating brain sections (40 μm, four to five sections/region) were immunostained and analyzed in cortical and limbic brain structures.
Results
FSS decreased circulating 3α,5α-THP (-41.6 ± 10.4 %) and reduced 3α,5α-THP immunolabeling in the paraventricular nucleus of the hypothalamus (-15.2 ± 5.7 %), lateral amygdala (LA, -31.1 ± 13.4 %), and nucleus accumbens (NAcc) shell (-31.9 ± 14.6). Within the LA, vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter were localized in 3α,5α-THP-positively stained cells, while in the NAcc shell, only VGLUT1 was localized in 3α,5α-THP-positively stained cells, suggesting that both glutamatergic and GABAergic cells within the LA are 3α,5α-THP-positive, while in the NAcc shell, 3α,5α-THP only localizes to glutamatergic cells. Conclusions: The decrease in circulating and brain levels of 3α,5α-THP may be due to alterations in the biosynthesis/metabolism or changes in the regulation of the HPA axis following FSS. Changes in GABAergic neuroactive steroids in response to stress likely mediate functional adaptations in neuronal activity. This may provide a potential targeted therapeutic avenue to address maladaptive stress responsivity.