brdu + doublecortin + zif268
BrdU was injected 3 weeks earlier, permanently labeling DNA in cells that were undergoing cell division. Therefore, this green BrdU+ cell (arrow) is 3 weeks-old. It is also generally immature, as it co-expresses doublecortin (DCX) which is typically found in migrating neurons or neurons that are extending axons and dendrites to connect with other neurons in the brain. However, we can say that this BrdU+ neuron has some degree of maturity, that it is functional and has synapses, since it expresses the immediate-early gene zif268, which is only expressed by neurons that have made synaptic connections and can be "activated". In this case, kainic acid was injected and used to induce widespread activation in the brain.