title: Reduction of circulating and selective limbic brain levels of (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP) following forced swim stress in C57BL/6J mice.
abstract: BACKGROUND
  Stress activates the hypothalamic-pituitary-adrenal (HPA) axis, and GABAergic neuroactive steroids contribute to homeostatic regulation of this circuitry. Acute forced swim stress (FSS) increases plasma, cortical, and hypothalamic (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP) levels in rats. However, there have not been systemic investigations of acute stress on changes in plasma and brain levels of 3α,5α-THP in mouse models.
  
  
  OBJECTIVE
  The present experiments aimed to assess circulating and local brain levels of 3α,5α-THP following acute FSS in C57BL/6J mice.
  
  
  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.
authors.affiliation: Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, 3027 Thurston Bowles Building, CB 7178, Chapel Hill, NC, 27599, USA.
authors.forename: Antoniette M
authors.initials: AM
authors.lastname: Maldonado-Devincci
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Beattie
authors.forename: Danielle H
authors.initials: DH
authors.lastname: Morrow
authors.forename: Raechel E
authors.initials: RE
authors.lastname: McKinley
authors.forename: Jason B
authors.initials: JB
authors.lastname: Cook
authors.forename: Todd K
authors.initials: TK
authors.lastname: O'Buckley
authors.forename: A Leslie
authors.initials: AL
authors.lastname: Morrow
mesh_terms: D000311:Adrenal Glands / Q000201:enzymology / Q000378:metabolism; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D003345:Corticosterone / Q000097:blood; D008032:Limbic System / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011280:Pregnanolone / Q000378:metabolism*; D013315:Stress, Psychological / Q000378:metabolism* / Q000523:psychology; D013550:Swimming / Q000523:psychology*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism; D050495:Vesicular Inhibitory Amino Acid Transport Proteins / Q000378:metabolism
chemical_list: C493465:Slc17a7 protein, mouse; D050598:Vesicular Glutamate Transport Protein 1; D050495:Vesicular Inhibitory Amino Acid Transport Proteins; C492244:Viaat protein, mouse; D011280:Pregnanolone; D003345:Corticosterone
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