Heterogeneity of GABA sub(A) Receptor-Mediated Responses in the Human IMR-32 Neuroblastoma Cell Line

• Published in: Journal of neuroscience research Vol. 60; no. 4; pp. 504 - 510
• Main Authors: Sapp, D W, Yeh, H H
• Format: Journal Article
• Language: English
• Published: 15-05-2000
• ISSN: 0360-4012
• DOI: 10.1002/(SICI)1097-4547(20000515)60:4<504::AID-JNR9>3.0.CO;2-Y

The gamma -aminobutyric acid (GABA) response profiles of IMR-32 human neuroblastoma cells were examined using whole-cell patch clamp and RT-PCR techniques. GABA activated a concentration-dependent and bicuculline-sensitive current, and RT-PCR revealed the expression of multiple GABA sub(A) receptor subunit mRNAs ( alpha sub(1), alpha sub(3), alpha sub(4), beta sub(1), beta sub(3), gamma sub(2), and delta ). A pharmacological profile of the GABA-induced current was derived using several subunit-selective agents. Diazepam, which requires the presence of a gamma subunit in order to modulate GABA sub(A) receptor-mediated responses, potentiated GABA-induced currents in a subset of IMR-32 cells. Two populations of GABA-activated currents were also evident based on sensitivity to modulation by zinc. Comparison of zinc- and diazepam-induced modulation of GABA-induced current responses in the same cells revealed an inverse correlation between these two modulators. No differences, however, were observed with the GABA sub(A) receptor modulators loreclezole, allopregnanolone, and pentobarbital. Thus, IMR-32 cells maintained in culture are heterogeneous in terms of expression of GABA sub(A) receptor isoforms.