Continuous infusion of substance P inhibits acute, but not subacute, inflammatory pain induced by complete Freund's adjuvant.

Previous studies have reported that continuous infusion with substance P (SP) into rat dorsal striatum ameliorated both mechanical allodynia in both formalin-evoked transient inflammatory pain and neuropathic pain models. However, a role of striatal SP in persistent inflammatory pain has not been demonstrated. The current study examined the effect of continuous infusion of SP into the rat dorsal striatum by reverse microdialysis on persistent inflammatory pain induced by complete Freund's adjuvant (CFA).

Continuous infusion of substance P into rat striatum relieves mechanical hypersensitivity caused by a partial sciatic nerve ligation via activation of striatal muscarinic receptors.

Previous studies have demonstrated that continuous substance P (SP) infusion into the rat striatum attenuated hind paw formalin-induced nociceptive behaviors and mechanical hypersensitivity via a neurokinin-1 (NK1) receptor dependent mechanism. However, whether there is a role of striatal infusion of SP on chronic, neuropathic pain has yet to be demonstrated. The present study investigated the effect of continuous SP infusion into the rat striatum using a reverse microdialysis method is antinociceptive in a rat model of chronic, mononeuropathic pain.

Continuous infusion of substance P into rat striatum alleviates nociceptive behavior via phosphorylation of extracellular signal-regulated kinase 1/2.

Intraplantar injection of 0.4% formalin into the rat hind paw leads to a biphasic nociceptive response; an 'acute' phase (0-15 min) and 'tonic' phase (16-120 min), which is accompanied by significant phosphorylation of extracellular signal-regulated kinase (ERK)1/2 in the contralateral striatum at 120 min post-formalin injection. To uncover a possible relationship between the slow-onset substance P (SP) release and increased ERK1/2 phosphorylation in the striatum, continuous infusion of SP into the striatum by reverse microdialysis (0.