title: Neurosteroids enhance spontaneous glutamate release in hippocampal neurons. Possible role of metabotropic sigma1-like receptors.
abstract: Pregnenolone sulfate (PREGS), one of the most abundantly produced neurosteroids in the mammalian brain, improves cognitive performance in rodents. The mechanism of this effect has been attributed to its allosteric modulatory actions on glutamate- and gamma-aminobutyric acid-gated ion channels. Here we report a novel effect of PREGS that could also mediate some of its actions in the nervous system. We found that PREGS induces a robust potentiation of the frequency but not the amplitude of miniature excitatory postsynaptic currents (mEPSCs) mediated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors in cultured hippocampal neurons. PREGS also decreased paired pulse facilitation of autaptic EPSCs evoked by depolarization, indicating that it modulates glutamate release probability presynaptically. PREGS potentiation of mEPSCs was mimicked by dehydroepiandrosterone sulfate and (+)-pentazocine but not by (-)-pentazocine, the synthetic (-)-enantiomer of PREGS or the inactive steroid isopregnanolone. The sigma receptor antagonists, haloperidol and BD-1063, blocked the effect of PREGS on mEPSCs, as did pertussis toxin and the membrane-permeable Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (acetoxymethyl) ester. These results suggest that PREGS increases spontaneous glutamate release via activation of a presynaptic G(i/o)-coupled sigma receptor and an elevation in intracellular Ca2+ levels. We postulate that presynaptic actions of neurosteroids have a role in the maturation and/or maintenance of synaptic networks and the processing of information in the central nervous system.
authors.affiliation: Department of Neurosciences, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131, USA.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Meyer
authors.forename: Mario
authors.initials: M
authors.lastname: Carta
authors.forename: L Donald
authors.initials: LD
authors.lastname: Partridge
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Covey
authors.forename: C Fernando
authors.initials: CF
authors.lastname: Valenzuela
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001665:Binding Sites; D002478:Cells, Cultured; D002490:Central Nervous System / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004594:Electrophysiology; D018698:Glutamic Acid / Q000378:metabolism*; D006220:Haloperidol / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin; D011284:Pregnenolone / Q000494:pharmacology; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D013256:Steroids / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D018094:Receptors, Metabotropic Glutamate; D013256:Steroids; D010566:Virulence Factors, Bordetella; C018370:pregnenolone sulfate; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D018698:Glutamic Acid; D004533:Egtazic Acid; D011284:Pregnenolone; D037342:Pertussis Toxin; D006220:Haloperidol