Scientists are working hard to understand how nerve pain works. The hope is to find a way to stop chronic nerve pain or even prevent it from occurring after a nerve injury.
In this animal study, rats were used to examine crushed nerve cells. The EphB/ephrinB system was the focus. This system is known to be part of the signaling mechanism for nerve pain.
Three groups of rats were included. One (experimental) group had a specific lumbar nerve root (L5) crushed. The second (sham) group had surgery to expose the nerve but nothing was done to it (no crush injury). The third (naive) group did not have any surgery done.
Nerve tissue was removed from all three groups and analyzed. The researchers were able to trace the levels of each protein and its receptor in the EphB/ephrinB system. They recorded the levels each day up to day 28 after surgery.
They found that ephrinB2 increased in the neurons (nerve cells) after nerve injury. It reached a maximum level on day seven and gradually decreased until day 28. Its receptor (EphB1) was increased in the spinal cord up to day 28.
In a second step of this experiment, a substance called small interference RNA (siRNA) was found to decrease pain levels. It does this by knocking out the ephrinB2.
The authors concluded that the ephrin system does play a role in nerve pain. It appears that there are specific receptors for ephrinB2 in the neurons of the spinal cord. These receptors are waiting for ephrinB2 to come along. If this signaling pathway can be interrupted, then scientists might be able to develop a drug using siRNA to block nerve pain.