Kinins are mediators of
pain and
inflammation and evidence suggests that the inducible
kinin B1 receptor (B1R) is involved in
neuropathic pain (NP). This study investigates whether B1R and TRPV1 are colocalized on nociceptors and/or astrocytes to enable regulatory interaction either directly or through the
cytokine pathway (IL-1β, TNF-α) in NP. Sprague Dawley rats were subjected to unilateral partial sciatic nerve
ligation (PSNL) and treated from 14 to 21 days post-PSNL with antagonists of B1R (
SSR240612, 10 mg·kg-1, i.p.) or TRPV1 (
SB366791, 1 mg·kg-1, i.p.). The impact of these treatments was assessed on nociceptive behavior and
mRNA expression of B1R, TRPV1, TNF-α, and IL-1β. Localization on primary sensory fibers, astrocytes, and microglia was determined by immunofluorescence in the lumbar spinal cord and dorsal root ganglion (DRG). Both antagonists suppressed PSNL-induced
thermal hyperalgesia, but only
SB366791 blunted mechanical and cold
allodynia.
SSR240612 reversed PSNL-induced enhanced
protein and
mRNA expression of B1R and TRPV1
mRNA levels in spinal cord while
SB366791 further increased B1R
mRNA/
protein expression. B1R and TRPV1 were found in non-
peptide sensory fibers and astrocytes, and colocalized in the spinal dorsal horn and DRG, notably with IL-1β on astrocytes. IL-1β
mRNA further increased under B1R or TRPV1 antagonism. Data suggest that B1R and TRPV1 contribute to
thermal hyperalgesia and play a distinctive role in
allodynia associated with NP. Close interaction and reciprocal regulatory mechanism are suggested between B1R and TRPV1 on astrocytes and nociceptors in NP.