Extra-Synaptic GABAA Receptor Potentiation and Neurosteroid-Induced Learning Deficits Are Inhibited by GR3027, a GABAA Modulating Steroid Antagonist

Objectives In Vitro: To study the effects of GR3027 (golexanolone) on neurosteroid-induced GABA-mediated current responses under physiological GABAergic conditions with recombinant human alpha 5 beta 3 gamma 2L and alpha 1 beta 2 gamma 2L GABAA receptors expressed in human embryonic kidney cells, using the response patch clamp technique combined with the Dynaflow (TM) application system. With alpha 5 beta 3 gamma 2L receptors, 0.01-3 mu M GR3027, in a concentration-dependent manner, reduced the current response induced by 200 nM THDOC + 0.3 mu M GABA, as well as the THDOC-induced direct gated effect. GR3027 (1 mu M) alone had no effect on the GABA-mediated current response or current in the absence of GABA. With alpha 1 beta 2 gamma 2L receptors, GR3027 alone had no effect on the GABA-mediated current response or did not affect the receptor by itself. Meanwhile, 1-3 mu M GR3027 reduced the current response induced by 200 nM THDOC + 30 mu M GABA and 3 mu M GR3027 that induced by 200 nM THDOC when GABA was not present. Objectives In Vivo: GR3027 reduces allopregnanolone (AP)-induced decreased learning and anesthesia in male Wistar rats. Rats treated i.v. with AP (2.2 mg/kg) or vehicle were given GR3027 in ratios of 1:0.5 to 1:5 dissolved in 10% 2-hydroxypropyl-beta-cyclodextrin. A dose ratio of AP:GR3027 of at least 1:2.5 antagonized the AP-induced decreased learning in the Morris Water Mase (MWM) and 1:7.5 antagonized the loss of righting reflex (LoR). GR3027 treatment did not change other functions in the rat compared to the vehicle group. Conclusions: GR3027 functions in vitro as an inhibitor of GABAA receptors holding alpha 5 beta 3 gamma 2L and alpha 1 beta 2 gamma 2L, in vivo, in the rat, as a dose-dependent inhibitor toward AP's negative effects on LoR and learning in the MWM.

Automated summary

Through in vitro and in vivo experiments, it was found that GR3027 has inhibitory effects on GABAA receptors, indicating its potential therapeutic value.