Hypoxia alters GABA A receptor function and subunit expression in NT2-N neurons

Abstract

Hypoxia causes dysfunction of excitatory and inhibitory neurotransmission, often resulting in encephalopathy, seizures or myoclonus. We evaluated the effects of hypoxia on GABA A receptor (GABA AR) function and expression in an in vitro model of neuronal hypoxia. NT2-N cells, derived from the human NT2 teratocarcinoma cell line, were exposed to ≤1% O 2 for 8 h and then used immediately for experiments or allowed to recover under normoxic conditions (95% air/5% CO 2) for 24, 48 or 96 h. Hypoxic treatment did not cause obvious morphological changes or cell death. In whole-cell patch-clamp recordings, the GABA current EC 50 was unchanged, however, maximal GABA-evoked currents changed in a biphasic manner. Maximal GABA currents were significantly increased immediately after hypoxia, but were significantly reduced after 48 h normoxic recovery, and then returned to baseline after 96 h recovery. Maximal potentiation of 10 μM GABA currents by diazepam was increased 48 h after hypoxia, but potentiation by zolpidem was decreased. Barbiturate enhancement and zinc inhibition of GABA currents were unchanged. Semiquantitative reverse transcriptase (RT)-PCR showed decreased α1, α5, β2 and γ2 subunit mRNA after hypoxia. Hypoxic exposure altered GABA AR physiology and subunit mRNA expression, which may correlate with symptoms observed after hypoxia in vivo.