Gabapentin decreases the level of
glutamate and elevates that of alpha-amino-
butyric acid in the central nervous system.
Gabapentin was shown to have antinociceptive effects in several facilitated
pain models. Intrathecal
gabapentin was also known to be effective in reducing
mechanical allodynia in animals with
neuropathic pain. In this study, we investigated to see whether intrathecal
gabapentin produces antihyperalgesic effects on thermal and
mechanical hyperalgesia in neuropathic rats and whether its effects are associated with motor impairment. To induce
neuropathic pain in Sprague-Dawley rats, left L5 and L6 spinal nerves were ligated. After a week, lumbar catheterization into subarachnoid space was performed. Then, paw withdrawal times to thermal stimuli and vocalization thresholds to paw pressure were determined before and up to 2 hr after
intrathecal injection of
gabapentin. Also, motor functions including performance times on rota-rod were determined. Intrathecal
gabapentin attenuated significantly thermal and
mechanical hyperalgesia in neuropathic rats, but did not block thermal and mechanical nociception in
sham-operated rats. Intrathecal
gabapentin of antihyperalgesic doses inhibited motor coordination performance without evident ambulatory dysfunction. This study demonstrates that intrathecal
gabapentin is effective against thermal and
mechanical hyperalgesia, in spite of moderate impairment of motor coordination.