Cold-aggravated pain in humans caused by a hyperactive Na(V)1.9 channel mutant

Gain-of-function mutations in the human SCN11A-encoded voltage-gated Na+ channel Na(V)1.9 cause severe pain disorders ranging from neuropathic pain to congenital pain insensitivity. However, the entire spectrum of the Na(V)1.9 diseases has yet to be defined. Applying whole-exome sequencing we here identify a missense change (p.V1184A) in Na(V)1.9, which leads to cold-aggravated peripheral pain in humans. Electrophysiological analysis reveals that p.V1184A shifts the voltage dependence of channel opening to hyperpolarized potentials thereby conferring gain-of-function characteristics to Na(V)1.9. Mutated channels diminish the resting membrane potential of mouse primary sensory neurons and cause cold-resistant hyperexcitability of nociceptors, suggesting a mechanistic basis for the temperature dependence of the pain phenotype. On the basis of direct comparison of the mutations linked to either cold-aggravated pain or pain insensitivity, we propose a model in which the physiological consequence of a mutation, that is, augmented versus absent pain, is critically dependent on the type of Na(V)1.9 hyperactivity

Cold-aggravated pain in humans caused by a hyperactive NaV1.9 channel mutantred

Gain-of-function mutations in the human SCN11A-encoded voltage-gated Na(+) channel Na(V)1.9 cause severe pain disorders ranging from neuropathic pain to congenital pain insensitivity. However, the entire spectrum of the Na(V)1.9 diseases has yet to be defined. Applying whole-exome sequencing we here identify a missense change (p.V1184A) in Na(V)1.9, which leads to cold-aggravated peripheral pain in humans. Electrophysiological analysis reveals that p.V1184A shifts the voltage dependence of channel opening to hyperpolarized potentials thereby conferring gain-of-function characteristics to Na(V)1.9. Mutated channels diminish the resting membrane potential of mouse primary sensory neurons and cause cold-resistant hyperexcitability of nociceptors, suggesting a mechanistic basis for the temperature dependence of the pain phenotype. On the basis of direct comparison of the mutations linked to either cold-aggravated pain or pain insensitivity, we propose a model in which the physiological consequence of a mutation, that is, augmented versus absent pain, is critically dependent on the type of Na(V)1.9 hyperactivity

The phosphodiesterase inhibitor rolipram delivered after a spinal cord lesion promotes axonal regeneration and functional recovery

Although there is no spontaneous regeneration of mammalian spinal axons after injury, they can be enticed to grow if cAMP is elevated in the neuronal cell bodies before the spinal axons are cut. Prophylactic injection of cAMP, however, is useless as therapy for spinal injuries. We now show that the phosphodiesterase 4 (PDE4) inhibitor rolipram (which readily crosses the blood–brain barrier) overcomes inhibitors of regeneration in myelin in culture and promotes regeneration in vivo. Two weeks after a hemisection lesion at C3/4, with embryonic spinal tissue implanted immediately at the lesion site, a 10-day delivery of rolipram results in considerable axon regrowth into the transplant and a significant improvement in motor function. Surprisingly, in rolipram-treated animals, there was also an attenuation of reactive gliosis. Hence, because rolipram promotes axon regeneration, attenuates the formation of the glial scar, and significantly enhances functional recovery, and because it is effective when delivered s.c., as well as post-injury, it is a strong candidate as a useful therapy subsequent to spinal cord injury