Nav1.7

Na_v1.7 is a sodium ion channel that in humans is encoded by the SCN9A gene. It is usually expressed at high levels in two types of neurons, the nociceptive (pain) neurons at dorsal root ganglion (DRG) and trigeminal ganglion, and sympathetic ganglion neurons, which are part of the autonomic (involuntary) nervous system.

Function

Na_v1.7 is a voltage-gated sodium channel and plays a critical role in the generation and conduction of action potentials and is thus important for electrical signaling by most excitable cells. Na_v1.7 is present at the endings of pain-sensing nerves, the nociceptors, close to the region where the impulse is initiated. Stimulation of the nociceptor nerve endings produces "generator potentials", which are small changes in the voltage across the neuronal membranes. The Na_v1.7 channel amplifies these membrane depolarizations, and when the membrane potential difference reaches a specific threshold, the neuron fires. In sensory neurons, multiple voltage-dependent sodium currents can be differentiated by their voltage dependence and by sensitivity to the voltage-gated sodium-channel blocker tetrodotoxin. The Na_v1.7 channel produces a rapidly activating and inactivating current which is sensitive to the level of tetrodotoxin. Na_v1.7 is important in the early phases of neuronal electrogenesis. Na_v1.7 activity consists of a slow transition of the channel into an inactive state when it is depolarized, even to a minor degree. This property allows these channels to remain available for activation with even small or slowly developing depolarizations. Stimulation of the nociceptor nerve endings produces "generator potentials", small changes in the voltage across the neuronal membranes. This brings neurons to a voltage that stimulate Na_v1.8, which has a more depolarized activation threshold that produces most of the transmembrane current responsible for the depolarizing phase of action potentials.