Study examines sodium channel variants in Neanderthals, modern-day humans

A report on Neanderthals in Current Biology found that some present-day humans carry a variant of the Neanderthal sodium channel, causing them to have increased pain sensitivity.

The variant has three different amino acids to the common variant, making it so that the carriers of the variant experience more pain, the report states. It was written by Hugo Zeberg, Michael Dannermann, Kristoffer Sahlholm, Hugh Robinson, Janet Kelso and Svante Paabo. 

Nav1.7, the sodium channel, is very important when it comes to pain pathways.

"In Neanderthals, the Nav1.7 protein carried three amino acid substitutions (M932L, V991L, and D1908G) relative to modern humans," the authors noted. "We expressed Nav1.7 proteins carrying all combinations of these substitutions and studied their electrophysiological effects."

The report notes that the single amino acid substitutions don't affect the ion channel function, but that the full variant carrying all of the substitutions shows the carriers are more sensitive to pain.

"We show that, due to gene flow from Neanderthals, the three Neanderthal substitutions are found in ~0.4% of present-day Britons, where they are associated with heightened pain sensitivity," the authors wrote.

The report noted that Nav1.7 is also in other types of cells, meaning that substitutions studied in the research may have other effects beyond pain modulation.

"However, given the electrophysiological effects of the substitutions, nociception, i.e., the input to the central nervous system from peripheral nerves in response to harmful or potentially harmful stimuli, is likely to have been higher in Neanderthals than in modern humans," the authors wrote. "The translation of such input into the conscious perception of pain is modulated both at the level of the spinal cord and the brain. Thus, it is not possible to conclude that Neanderthals necessarily experienced more pain than modern humans do."

The authors wrote that Neanderthal peripheral nerve endings gave them the ability to be more sensitive to stimuli. They said they could only guess about the consequences of having the substitutions in homozygous form.