Gene expression profile after intense second messenger activation in cortical primary neurones

Numerous stimuli induce immediate early gene (IEG) expression in neurones, but a comprehensive overview of the late-response genes is lacking. Therefore we aimed to identify changes in the neuronal gene expression profile following intense stimulation. Forskolin and 12-O-tetradecanoylphorbol-13-acetate (TPA), direct activators of intracellular second messengers, were applied to primary cultured cortical neurones. The gene expression profiles were analyzed on Affymetrix DNA chips which cover around 8000 rat genes. Out of these, 95 genes (1.2%) were increased at least three-fold, and 43 genes (0.5%) were at least three-fold decreased. The gene chip results were verified by testing 15 of the altered genes by quantitative real-time PCR. The majority of the up-regulated genes were transcription factors, neurotrophic factors or (putative) neuropeptides. Furthermore, there were marked changes in intracellular signal processing enzymes and in postsynaptic structural proteins (e.g. vesl, arc, narp), which have been implicated in synaptic plasticity. Notably, classical players in neurotransmission or plasticity such as glutamate and GABA receptors or voltage-gated ion channels were not increased. It is likely that the increased production of components of intracellular signalling and of postsynaptic proteins is involved in neuronal plasticity.