Effect of deafferentation on the levels of uric acid in the spinal cord of the rat.

In previous studies we reported that the rat spinal cord contains relatively high levels of uric acid and that the levels in a rat model of bilateral chronic pain, experimental adjuvant arthritis. In this report we evaluate the changes in UA in the unilaterally deafferented rat, a preparation which has also been used to study chronic pain. Uric acid was measured by high-pressure liquid chromatography with electrochemical detection in the spinal cord of rats that underwent unilateral, multiple cervical dorsal rhizotomy. Compared to control and sham-operated rats, there was a significant increase in the level of uric acid in the dorsal quadrant of the spinal cord ipsilateral to the dorsal rhizotomy. This increase was present at 1 and 4 weeks after surgery. At 1 week, we also observed a small but statistically insignificant increase in uric acid levels in the dorsal quadrant contralateral to the deafferentation and in sham-operated rats. Four weeks after surgery the levels of UA in all regions except for the deafferented dorsal quadrant returned to normal. The possibility was raised that the changes in uric acid reflect an increase in purinergic metabolism in the spinal cord secondary to the increased activity of the dorsal horn neurons that occurs with deafferentation.