NaTasha Clark
A New Strategy to Treat Neuropathic Pain in Rats

SchoolCleveland School of Science and Medicine at John Hay


ProgramScience


MentorJianguo Cheng, MD, PhD


DepartmentPain Management and Neurosciences


Research
A New Strategy to Treat Neuropathic Pain in Rats
Hypothesis
The combination of local anesthetics QX-314 together with capsaicin will reduce pain in rats and increase the threshold to noxious stimulation.
Methodology
We performed a sciatic nerve surgery to produce neuropathic pain in the rat’s hind leg. Either QX-314, capsaicin, lidocaine or the combination of QX-314 and capsaicin were injected near the sciatic nerve to reduce pain. Behavioral tests were performed before and after the injection. Thermal hyperalgesia tested sensitivity to heat and mechanical hyperalgesia tested sensitivity to touch. Each test group had six rats.
Outcomes
The hypothesis was correct. When we injected the QX-314 followed by the capsaicin, pain was reduced. The withdrawal latencies to thermal stimulation were around 12 seconds before the injection of the combination of QX-314 and capsaicin, but increased to 17 seconds afterward. Importantly, the motor functions were not affected to any observable extent. Similar results were observed for mechanical stimulation tests. The rats withdrew the hind paw in response to mechanical or thermal stimulation. Before injection, the mechanical withdrawal thresholds were around 6(g). After injection of QX-314 and capsaicin, the thresholds increased to 15(g). This increase lasted for more than an hour. In contrast, either capsaicin or QX-314 alone did not increase the thresholds to thermal and mechanical stimulation. Lidocaine increased thermal and mechanical thresholds, but it caused significant motor blockade.

Interpretations

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