The material in a .docx format: Discussion_5_Paper_Questions
Paper Title: “An SCN9A channelopathy causes congenital inability to experience pain” Cox, 2006.
- Supplemental Data
SCN9a encodes the alpha subunit of the Nav1.7 voltage-gated Na+ channel. Together with SCN1b & SCN2b, these create a functional Nav1.7 channel. Nav1.7 is expressed in 2 tissues, nociceptive DRG neurons and sympathetic ganglion neurons. For the detection of pain, the nociceptive DRG neurons are essential.
The Nav1.7 gene functions as an “amplifier” of nociception. Nociception is the detection/perception of pain, and is activated by nociceptors in nerve fibers. Nociceptors are a type of sensory receptor which responds to pain. In response to pain, nociceptors produce “generator potentials.” In this case, they are small voltage depolarizations across the neuronal membrane in DRG neurons. When there are small depolarizations from nociceptors, the Nav1.7 channel amplifies the initial generator potential, further depolarizing the neuron. If enough depolarization is reached, an AP is initiated. To clarify, the Nav1.7 does not detect the painful stimuli, it amplifies the initial detection, thus an “amplifier.”