Evidence that pregabalin reduces neuropathic pain by inhibiting the spinal release of glutamate.

Pregabalin is an anti-convulsant that successfully treats many neuropathic pain syndromes, although the mechanism of its anti-hyperalgesic action remains elusive. This study aims to help delineate pregabalin's anti-hyperalgesic mechanisms. We assessed the effectiveness of pregabalin at decreasing mechanical and cold hypersensitivity induced in a rat model of neuropathic pain. Thus, we compared the effectiveness of pre- or post-treatment with systemic or intrathecal (i.t.) pregabalin at reducing the development and maintenance of the neuropathic pain symptoms. Pregabalin successfully decreased mechanical and cold hypersensitivity, as a pre-treatment, but was less effective at suppressing cold hypersensitivity when administered as a post-treatment. Furthermore, both i.t. and systemic administration of pregabalin were effective in reducing the behavioral hypersensitivity, with the exception of systemic post-treatment on cold hypersensitivity. We also examined pregabalin's effects at inhibiting hind paw formalin-induced nociception in naïve rats and formalin-induced release of excitatory amino acids in the spinal cord dorsal horn (SCDH) both in naïve rats and in rats with neuropathic pain. Pregabalin dose-dependently reduced nociceptive scores in the formalin test. We also present the first evidence that pregabalin reduces the formalin-induced release of glutamate in SCDH. Furthermore, i.t. pregabalin reduces the enhanced noxious stimulus-induced spinal release of glutamate seen in neuropathic rats. These data suggest that pregabalin reduces neuropathic pain symptoms by inhibiting the release of glutamate in the SCDH.