Everyone knows that people react differently to pain: the initial jab of Novocain at a dentist’s office causes excruciating discomfort for some, while others barely seem to mind. But is that because some people truly feel more pain than others in a given circumstance (such as an injection) or because some people can just suck it up better?
A new study by Frank Reimann and colleagues at Cambridge Institute for Medical Research suggests the former may be true, even though it doesn’t completely rule-out the whimp factor.
Reimann’s group reported in the Proceedings of the National Academy of Sciences that variations in the SCN9A gene were associated with changes in the perception of pain.
To reach this conclusion, they studied kids with a rare condition characterized by an inability to detect pain. These kids can pass knives through their arms and walk across hot coals without a flinch. Reimann’s group found this extremely maladaptive condition was associated with a nonfunctioning SCN9A gene.
The scientists reasoned that polymorphism at the SCN9A locus could cause differing pain thresholds, and tested their hypothesis by examining DNA from 578 people with osteoarthritis. They found that folks having a common variant of the SCN9A gene had lower pain self-assessment scores than those having a rarer form of the gene.
The scientists reproduced their findings in people with back pain, pancreatitis and phantom limb pain.
The SCN9A gene it turns out, codes for a membrane-bound protein on pain sensory nerve cells. The protein is involved with triggering those cells, which then relay a pain message to the brain. Apparently, the version of the protein created by the rare SCN9A decreases firing thresholds in the cells so they are more likely to relay bad news.