The Tangled Bank

In the recent article of Nature(December, 2005) there was an interesting article called A painful factor which delves into the subject of allodynia or Neuropathic pain, which is pain that results from a non-injurious stimulus to the skin. The general known cause of this disorder is damage to the nerves that transmit sensory information (temperature, touch, etc.), and people with this condition experience crippling pain in response to a stimulus that is not painful normally. More, however is continually being learned about these mechanisms.
Recently it has been found, through research done by Coull et. al. (research which was also published in this issue) that injury to the nerves activates scavenger cells or microglia in the spinal cord which results in neuropathic pain. They have also shown that there is a critical link between the activation of microglia and altered sensory to neuronal processing. More specifically, a neuronal modulating protein called BDNF (brain-derived neurotrophic factor) was discovered to be the main mediator in signalling between microglia and neurons during neuropathic pain.
Experiments performed in the rat model proved that disrupting BDNF signalling was able to reverse allodynia which was already established. Many questions still have to be answered, including what signalling pathway eventually leads to the release of BDNF, but the outlook is optimistic for future treatments