arnab gupta

The rat that’s ‘immune’ to acid

December 16, 2011

Very interesting article here about why the naked mole rat can’t feel pain from acid burns. Apparently it was already known that they don’t feel the pain; their hypothesis about why it happened—that the acid sensing ion channels that tell neurons to transmit pain would be missing—was not true.

Because it turns out that mole rats — despite being the only known vertebrates that are insensitive to the painful stimulus of acid — have the same two fully-functional, acid-sensing channels regulating their pain receptors as the rest of us, and even produce the channels in similar quantities. And this is where things get interesting.

Now they know the actual reason. There’s another way neuron-firing can be controlled, and it is this (sodium) channel that is highly inhibited in the naked rat mole. Similar phenomenons are observed in humans too:

Furthermore — and this doesn’t happen often — humans lacking the Nav1.7 channel have been known to feel no pain whatsoever.

Very interesting, yes, but my question is this: the naked rat mole is insensitive to pain due to acids; but does that mean that it is in fact unaffected by acids? It does not seem so—the phenomenon is purely neurological, and there seems to be nothing physiological that would protect the rat against acids.

Does this not make this a counterproductive adaptation? Why would this adaptation survive? Is it because the natural environments of these rats are entirely devoid of harmful acids, thus making that pain sensation redundant? (Is this also why they’re “naked”, rather than furry?)