Dual potentiating and inhibitory actions of a benz[e]indene neurosteroid analog on recombinant α1β2γ2 GABAA receptors
Dual potentiating and inhibitory actions of a benz[e]indene neurosteroid analog on recombinant α1β2γ2 GABAA receptors
复制标题
DOI：
10.1124/mol.106.022590
复制
发表时间：
2006-06-01
影响因子：
3.6
通讯作者：
Akk, Gustav
中科院分区：
文献类型：
--
作者：
Li, Ping;Covey, Douglas F.;Akk, Gustav
Benz[e]indenes are tricyclic analogs of neuroactive steroids and can be modulators of GABA A receptor activity. We have examined the mechanisms of action of the benz[ e] indene compound [3S-(3 alpha,3a alpha,5a beta,7 beta,9a alpha,9b beta)]-dodecahydro-7-(2-hydroxyethyl)3a-methyl-1H-benz[e]indene-3-carbonitrile (Bl-2) using single-channel patch-clamp and whole-cell recordings from human embryonic kidney cells transfected with rat GABA A receptor alpha 1, beta 2, and gamma 2L subunits. The data demonstrate that Bl-2 is a positive modulator of GABA A receptor activity with a peak effect at 2 mu M. The mechanism of modulation is similar but not identical to that of neuroactive steroids. Similar to steroids, Bl-2 acts by prolonging the mean open time duration through an effect on the duration and prevalence of the longest open time component. However, in contrast to many steroids, Bl-2 does not selectively reduce the channel closing rate. The potentiating action of Bl-2 seems to be mediated through interactions with the classic neuroactive steroid binding site. Mutation to the membrane-spanning region in the alpha 1 subunit Q242W and the double mutation alpha 1N408A/Y411F, previously shown to abolish potentiation by neurosteroids, also diminish potentiation by Bl-2. At higher concentrations (> 5 mu M), Bl-2 inhibits receptor function by enhancing the apparent rate of desensitization. From single-channel recordings, we estimate that the entry rate into the inhibited or blocked state, k(+B), is 0.50 mu M-1 s(-1). Based on the kinetic mechanism of action, and the finding that this effect is blocked by the alpha 1V256S mutation, we propose that Bl-2 acts through an inhibitory site first postulated for the inhibitory neurosteroid pregnenolone sulfate.
