The process of synapse formation and assembly of neuronal circuits can be studied in vitro using primary hippocampus neuronal culture. Previous proteomic studies have characterised around 1000 proteins in the Post Synaptic Proteome (PSP) and 185 proteins in the NMDA receptor complex (NRC) (see Collins et al, SfN 2005). We have addressed the assembly of the PSP and NRC using gene expression profiles in cultured neurons. In addition, it is possible to correlate changes in gene expression with developmental changes in electrophysiological properties. For these purposes, we have combined two distinct microarray technologies: high density oligonucleotide arrays for genome wide transcriptome profiling (Murine Genome 430 2.0 array, Affymetrix) and multielectrode array technology (Multichannel Systems) for recording activity in populations of neurons. Data was collected at time points between day 1 and day 25 during which time there was a sigmoidal increase in action potential firing and emergence of complex firin...