Scientists identifiy new type of pain-sensing neuron in rats

We all know that if you put your hand over an open flame it's very painful. What you may not know is that, for some people, just lying under a blanket is painful as well. They have neuropathic pain--annoying, chronic pain that comes from a diseased nerve cell rather than a specific stimulus. Feeling phantom pain in a missing limb is another, more famous, example.

Experts say up to two percent of the U.S. population suffers from neuropathic pain. But this pain generally responds poorly to analgesics and other standard treatment and get worse over time, causing permanent disability in some people. Now there may be new hope for these pain sufferers.

Scientists at the University of Virginia Health System have identified a new type of pain-sensing neuron in rats, which are unusually dense in a subtype of calcium channels called T-type channels. It is possible that these "T-rich cells" could be targets for future therapies to treat neuropathic pain as well as acute onset pain, which can happen after invasive surgery or inflammation.

A UVa anesthesiologist, Dr. Slobodan Todorovic, and his colleagues identified these novel cells and believe that the T-type calcium channels in them may serve as a volume control for pain impulses. "We hope that this new type of neuron will be amenable to new therapies. The next step will be to find a drug to block the action of these calcium channels," Todorovic said.

It was once thought that calcium channels were only important for brain function. But, Todorovic and his team show that the T-type channels are important to the functioning of peripheral nerves, especially when the nerves are injured.

A PhD student in UVa's neuroscience graduate program, Mike Nelson, discovered these T-rich nerve cells in Todorovic' lab. "It's very exciting to make an initial observation like this," Nelson said. "It's one reason we go to grad school in the first place." There are no drugs now that effectively treat neuropathic pain, Nelson added. "Hopefully, observations like this will lead to new and more efficacious drugs in the future. Our findings are another piece of evidence that these calcium channels are excellent targets for new analgesic development."