GABA(A) receptors expressed in undifferentiated human teratocarcinoma NT2 cells differ from those expressed by differentiated NT2-N cells

During CNS development, changes occur in expression of GABA(A) receptor sub unit subtypes and GABA(A) receptor pharmacological and biophysical properti es. We used reverse transcription PCR and whole-cell-recording techniques t o determine whether GABA(A) receptor expression and function also changed d uring retinoic acid-induced differentiation of human Ntera 2 (NT2) teratoca rcinoma cells into neuron-like cells (NT2-N cells). In undifferentiated NT2 cells only alpha 5, beta 3, gamma 3, and pi subtype mRNAs were detected. N T2 GABA(A) receptor currents had a maximal amplitude of 52 pA and an EC50 o f 4.0 mu M, were relatively insensitive to enhancement by zolpidem and diaz epam, and were enhanced by loreclezole and inhibited by lanthanum, zinc, an d furosemide. In contrast, in NT2-N cells after 13 weeks of retinoic acid t reatment, all GABA(A) receptor subtype mRNAs were detected. Maximal peak wh ole-cell currents were similar to 50-fold larger than NT2 cell currents, an d the GABA EC50 was higher (39.7 mu M). In 13 week NT2-N cells, diazepam, z olpidem, loreclezole, and lanthanum had only small effects on GABA(A) recep tor currents, and the zinc IC50 for current inhibition was significantly hi gher than that for NT2 cells. In a previous study, we showed that NT2-N cel ls after 5 weeks of retinoic acid treatment had moderate peak currents, GAB A EC50, and zinc IC50 but that currents were robustly enhanced by diazepam, zolpidem, and loreclezole. During differentiation of NT2 cells to NT2-N ce lls, GABA(A) receptors underwent changes in subunit expression and pharmaco logy that were similar to many of the developmental changes in GABA(A) rece ptors that occur in CNS neurons.