Abstract
Gabapentin decreases the level of glutamate and elevates that of garmma-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.