The Journal of Neuroscience, August 15, 1999, 19(16):7057-7065
GABAA Receptors Expressed in Undifferentiated Human
Teratocarcinoma NT2 Cells Differ from Those Expressed by Differentiated
NT2-N Cells
Torben R.
Neelands1,
Jie
Zhang1, and
Robert L.
Macdonald2, 3
1 Graduate Program in the Neurosciences and Departments
of 2 Neurology and 3 Physiology, University of
Michigan Health Sciences Center, Ann Arbor, Michigan 48104-1687
During CNS development, changes occur in expression of
GABAA receptor subunit subtypes and GABAA
receptor pharmacological and biophysical properties. We used reverse
transcription PCR and whole-cell-recording techniques to
determine whether GABAA receptor expression and function
also changed during retinoic acid-induced differentiation of human
Ntera 2 (NT2) teratocarcinoma cells into neuron-like cells
(NT2-N cells). In undifferentiated NT2 cells only
5,
3,
3, and
subtype mRNAs were detected. NT2 GABAA receptor
currents had a maximal amplitude of 52 pA and an EC50 of
4.0 µM, were relatively insensitive to enhancement by
zolpidem and diazepam, and were enhanced by loreclezole and inhibited
by lanthanum, zinc, and furosemide. In contrast, in NT2-N cells after
13 weeks of retinoic acid treatment, all GABAA receptor
subtype mRNAs were detected. Maximal peak whole-cell currents were
~50-fold larger than NT2 cell currents, and the GABA EC50
was higher (39.7 µM). In 13 week NT2-N cells, diazepam, zolpidem, loreclezole, and lanthanum had only small effects on GABAA receptor currents, and the zinc IC50 for
current inhibition was significantly higher than that for NT2 cells. In
a previous study, we showed that NT2-N cells after 5 weeks of retinoic
acid treatment had moderate peak currents, GABA EC50, and
zinc IC50 but that currents were robustly enhanced by
diazepam, zolpidem, and loreclezole. During differentiation of NT2
cells to NT2-N cells, GABAA receptors underwent changes in
subunit expression and pharmacology that were similar to many of the
developmental changes in GABAA receptors that occur in CNS neurons.
Key words:
GABA; GABAA receptor; electrophysiology; patch clamp; RT-PCR; Ntera2; loreclezole; benzodiazepine; zinc; differentiation; NT2 cells; NT2-N cells
Copyright © 1999 Society for Neuroscience 0270-6474/99/19167057-09$05.00/0