title: Characterization of brain neurons that express enzymes mediating neurosteroid biosynthesis.
abstract: Allopregnanolone (ALLO) and tetrahydrodeoxycorticosterone (THDOC) are potent positive allosteric modulators of GABA action at GABA(A) receptors. ALLO and THDOC are synthesized in the brain from progesterone or deoxycorticosterone, respectively, by the sequential action of two enzymes: 5alpha-reductase (5alpha-R) type I and 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD). This study evaluates 5alpha-R type I and 3alpha-HSD mRNA expression level in mouse brain by using in situ hybridization combined with glutamic acid decarboxylase 67/65, vesicular glutamate transporter 2, glial fibrillary acidic protein, and S100beta immunohistochemistry. We demonstrate that 5alpha-R type I and 3alpha-HSD colocalize in cortical, hippocampal, and olfactory bulb glutamatergic principal neurons and in some output neurons of the amygdala and thalamus. Neither 5alpha-R type I nor 3alpha-HSD mRNAs are expressed in S100beta- or glial fibrillary acidic protein-positive glial cells. Using glutamic acid decarboxylase 67/65 antibodies to mark GABAergic neurons, we failed to detect 5alpha-R type I and 3alpha-HSD in cortical and hippocampal GABAergic interneurons. However, 5alpha-R type I and 3alpha-HSD are significantly expressed in principal GABAergic output neurons, such as striatal medium spiny, reticular thalamic nucleus, and cerebellar Purkinje neurons. A similar distribution and cellular location of neurosteroidogenic enzymes was observed in rat brain. Taken together, these data suggest that ALLO and THDOC, which can be synthesized in principal output neurons, modulate GABA action at GABA(A) receptors, either with an autocrine or a paracrine mechanism or by reaching GABA(A) receptor intracellular sites through lateral membrane diffusion.
authors.affiliation: Department of Psychiatry, Psychiatric Institute, University of Illinois, 1601 Taylor Street, Chicago, IL 60612, USA.
authors.forename: Roberto C
authors.initials: RC
authors.lastname: Agís-Balboa
authors.forename: Graziano
authors.initials: G
authors.lastname: Pinna
authors.forename: Adrian
authors.initials: A
authors.lastname: Zhubi
authors.forename: Ekrem
authors.initials: E
authors.lastname: Maloku
authors.forename: Marin
authors.initials: M
authors.lastname: Veldic
authors.forename: Erminio
authors.initials: E
authors.lastname: Costa
authors.forename: Alessandro
authors.initials: A
authors.lastname: Guidotti
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific) / Q000235:genetics / Q000378:metabolism*; D000679:Amygdala / Q000166:cytology / Q000201:enzymology; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002531:Cerebellum / Q000166:cytology / Q000201:enzymology; D002540:Cerebral Cortex / Q000166:cytology / Q000201:enzymology; D003342:Corpus Striatum / Q000166:cytology / Q000201:enzymology; D003900:Desoxycorticosterone / Q000031:analogs & derivatives* / Q000096:biosynthesis; D015971:Gene Expression Regulation, Enzymologic; D006624:Hippocampus / Q000166:cytology / Q000201:enzymology; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D009830:Olfactory Bulb / Q000166:cytology / Q000201:enzymology; D011280:Pregnanolone / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D013788:Thalamus / Q000166:cytology / Q000201:enzymology
chemical_list: D008565:Membrane Proteins; D012333:RNA, Messenger; D003900:Desoxycorticosterone; C009413:tetrahydrodeoxycorticosterone; D011280:Pregnanolone; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; C518406:Srd5a1 protein, mouse; C476566:steroid-5alpha-reductase type 1