Expression of heteromeric glycine receptor-channels in rat spinal cultures and inhibition by neuroactive steroids.
Ionotropic glycine receptors were studied in cultured spinal cord neurons prepared from 17-day-old rat embryos, using whole-cell patch clamp electrophysiology. Glycine receptors of 3-17 days in vitro were characterized via subtype-specific channel blockade by micromolar picrotoxin and cyanotriphenylborate, as well as nanomolar strychnine. Potentiation by nanomolar tropisetron indicated coexpression of beta with alpha subunits. The neuroactive steroids pregnenolone sulfate and dehydroepiandrosterone sulfate, as well as alphaxalone and its 3beta epimer betaxalone inhibited the chloride current with IC(50) values of 19, 46, 16 and 208 microM, respectively, with no potentiation. Reverse transcription polymerase chain reaction and immunocytochemistry demonstrated mRNAs and proteins of alpha1, alpha2, alpha3 and beta subunits in rat spinal cord cultures. In conclusion, neuroactive steroids, both positive and negative modulators of gamma-aminobutyric-acid(A) receptors, inhibited heteromeric glycine receptors at micromolar concentrations.
Fodor
László
L
Pharmacology and Drug Safety Research, Gedeon Richter Ltd., POB 27, H-1475 Budapest, Hungary. l.fodor@richter.hu
Boros
András
A
Dezso
Péter
P
Maksay
Gábor
G
D000818:Animals; D018118:Chloride Channels / Q000187:drug effects; D003627:Data Interpretation, Statistical; D003687:Dehydroepiandrosterone / Q000494:pharmacology; D004594:Electrophysiology; D005998:Glycine / Q000494:pharmacology; D007150:Immunohistochemistry; D007211:Indoles / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011277:Pregnanediones / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D018009:Receptors, Glycine / Q000819:agonists / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013050:Spectrometry, Fluorescence; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013256:Steroids / Q000494:pharmacology*; D013654:Taurine / Q000494:pharmacology; D000077526:Tropisetron
D018118:Chloride Channels; D007211:Indoles; D011277:Pregnanediones; D012333:RNA, Messenger; D018009:Receptors, Glycine; D013256:Steroids; D013654:Taurine; D003687:Dehydroepiandrosterone; D000077526:Tropisetron; C006477:alphaxalone; D005998:Glycine