The neuroactive steroids alphaxalone and pregnanolone increase the conductance of single GABAA channels in newborn rat hippocampal neurons

Simon Gaul, Nesrin Ozsarac, Lu Liu, Rainer H.A. Fink*, Peter W. Gage

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    12 Citations (Scopus)

    Abstract

    The effects of the neuroactive steroids alphaxalone and pregnanolone on single GABAA receptor channels were tested in cell-attached and inside-out patches from cultured newborn rat hippocampal neurons. The conductance of these single channels ranged between 10 and 80 pS when exposed to low (0.5-3 μM) GABA concentrations. These GABA concentrations activated low-conducting channels (<40 pS) in 78% of the patches, 22% of patches had channels with a maximum conductance above 40 pS. Alphaxalone at concentrations above 1 μM, and pregnanolone at concentrations above 0.1 μM, significantly increased the conductance of initially low-conducting single channels activated by GABA up to seven-fold and at all concentrations tested, both drugs increased open probability and mean open time and decreased closed probability and mean closed time of channels. Both steroids at higher concentrations could directly activate high conductance (>40 pS) chloride channels. Both the directly activated channels and those channels that had been previously affected by alphaxalone were modulated by diazepam, a benzodiazepine drug that is known to specifically modulate GABAA channels. The present study is the first one to show that neurosteroids can significantly increase single GABAA channel conductance, thus enlarging our current knowledge on the molecular mechanism of action of these compounds.

    Original languageEnglish
    Pages (from-to)35-44
    Number of pages10
    JournalJournal of Steroid Biochemistry and Molecular Biology
    Volume104
    Issue number1-2
    DOIs
    Publication statusPublished - Apr 2007

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