Figure 3

Chronic activity blockade or prolonged NMDAR inhibition reduces gene expression of K ⁺ channels. (A,B) Rat dissociated hippocampal neurons cultured at high density (DIV 12–14) were treated with the NMDAR antagonist APV (100 μM) or control (CTL-H₂O, 0.1% H₂O) for 48 h. (A) Representative spike trains are shown. (B) Average AP firing rates (Hz) measured in pyramidal neurons treated for 48 h with CTL-H₂O (n = 9) or APV (n = 9) for 48 h. APV treatment significantly increased AP firing frequency compared to CTL-H₂O treatment. (C,D) QPCR validation of select genes involved in intrinsic excitability (C) and synaptic transmission (D) identified by microarray analysis (n = 5 per treatment). The mRNA levels of all samples were normalized to the housekeeping gene GAPDH, which was unaffected by these treatments. Following normalization to GAPDH cDNA levels, the relative fold change for each treatment compared to reference control was determined and has been shown. Treatment with TTX or APV decreased the mRNA levels of most of the tested K⁺ channel genes. In contrast, BC application had no effect on most K⁺ channel genes except for KCNA1 and LGI1 which were up-regulated. The ★ denotes genes whose protein products have not previously been implicated in homeostatic plasticity. Mean ± SEM (*p < 0.05, **p < 0.01).