Researchers have identified a bio-chemical circuit that supports neuron-microglia communication. When neurons are active, they release ATP. Microglia sense extracellular ATP and the compound draws the immune cell toward the neuron.circuit that supports neuron-microglia communication. When neurons are active, they release ATP. Microglia sense extracellular ATP and the compound draws the immune cell toward the neuron.circuit that supports neuron-microglia communication. When neurons are active, they release ATP. Microglia sense extracellular ATP and the compound draws the immune cell toward the neuron.