Recombinant Rabbit Monoclonal anti-Npas4 Antibody We have developed an anti-Npas4 recombinant rabbit monoclonal antibody with high specificity demonstrated in Npas4 KO mice. This Npas4 antibody can be used to mark active neurons in brain slices and in primary cultures. The Ab has worked well in all methods tested, including Western blotting, immunohistochemistry, immunocytochemistry, ChIP-Seq and iDISCO whole brain staining. Npas4 as a Marker of Recent Neuronal Activity Neuronal activity engages biochemical signaling pathways that produce alterations in gene expression leading to long-term adaptive changes in neurons that are fundamental to behavioral plasticity. Thus, immediate-early gene (IEG) induction is commonly used to visualize recent neuronal activity. However, the IEGs traditionally used to mark neuronal activity (e.g., arc, cfos and egr1/zif268) are also turned on by extrinsic factors such as neurotrophins and neuromodulators that raise cAMP. In contrast, the neuron-specific IEG npas4is strongly induced by neuronal activity, but does not respond to these other factors (Lin et al., 2008). Further, Npas4 expression is more rapid and transient than other IEGs (Ramamoorthi et al., 2011). This tight tuning to neuronal activity makes Npas4 an ideal marker of neuronal activity in the brain.