Strichartz and colleagues were surprised that although they found a correlation between gabapentin’s ability to reduce both evoked pain and resting pain, morphine did not have the same effect. “Morphine produced reduced evoked pain as much as gabapentin did but caused no difference in place preference, so appears to have no effect on resting pain,” Strichartz said. “This selective attenuation of evoked pain without relieving resting pain suggests that those different forms of pain have different mechanisms.”

Additional Ongoing Research

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Dr. Strichartz explained that he and colleagues have conducted other studies evaluating the role of brain and spinal cord in post-thoracotomy pain. In an interview, he described how investigators used a specific molecule of synthetic “toxin” that kills only a specific population of cells when it is “micro-injected” into the brainstem, in the rostro-ventral medulla (RVM). Strichartz said this is the region of the brain where opioids act, and nerve fibers travel to the spinal cord, where they inhibit trafficking of pain impulses coming from the periphery, such as those coming from the area around a thoracotomy. “We found that if we destroyed these neurons, 90 to 95 percent of neurons were destroyed before thoracotomy, none of the animals experienced post-thoracotomy pain,” says Strichartz.

In other closely related experiments, Dr. Strichartz and colleagues performed a thoracotomy with this same rat model and then killed the same set of neurons with the selective toxin injected into the RVM.