Calcium Control of Gene Regulation in Rat Hippocampal Neuronal Cultures

Blockage of GABA-A receptors in hippocampal neuronal cultures triggers synchronous bursts of spikes initiating neuronal plasticity, partly mediated by changes of gene expression. By using specific pharmacological blockers, we have investigated which sources of Ca2þ entry primarily control changes of gene expression induced by 20 mM gabazine applied for 30 min (GabT). Intracellular Ca2þ transients were monitored with Ca2þ imaging while recording electrical activity with patch clamp microelectrodes. Concomitant transcription profiles were obtained using Affymetrix oligonucleotide microarrays and confirmed with quantitative RT-PCR. Blockage ofNMDAreceptors with 2-amino-5-phosphonovaleric acid (APV) did not reduce significantly somatic Ca2þ transients, which, on the contrary, were reduced by selective blockage of L, N, and P/Q types voltage gated calcium channels (VGCCs). Therefore, we investigated changes of gene expression in the presence of blockers of NMDA receptors and L, N, and P/Q VGCCs. Our results show that: (i) among genes upregulated by GabT, there are genes selectively dependent on NMDA activation, genes selectively dependent on L-type VGCCs and genes dependent on the activation of both channels; (ii) the majority of genes requires the concomitant activation of NMDA receptors and Ca2þ entry through VGCCs; (iii) blockage of N and P/Q VGCCs has an effect similar but not identical to blockage of L-type VGCCs.