Original Articles

Effects of complete Freund's adjuvant on immunohistochemical distribution of IL-1β and IL-1R I in neurons and glia cells of dorsal root ganglion

Man LI, Jing SHI, Jun-rui TANG, Di CHEN, Bo AI, Jun CHEN, Li-na WANG, Fu-yuan CAO, Ling-li LI, Chuan-you LIN, Xin-min GUAN


Aim: To investigate the effects of complete Freund’s adjuvant (CFA) on inflammatory
hyperalgesia and morphological change of the coexsistence of interleukin-1
beta (IL-1β) and type I IL-1 receptor (IL-1RI) in neurons and glia cells of rat dorsal
root ganglion (DRG). Methods: The pain-related parameters and the expression of
IL-1RI and IL-1β positive neurons and glia cells of DRG in normal saline (NS) and
adjuvant-induced arthritic (AA) group were examined with pain behavior assessment
methods and immunohistochemical assay, respectively. Results: Five hours,
1 d, and 2 d after intra-articular injection of 50 μL CFA, tactile hyperalgesia induced
by CFA was observed in the foot flexion and extension scores of the ipsilateral
hindpaw of AA group. Three days after injection, the distribution of IL-1RI/
IL-1β double-stained coexisted neurons and glia cells were observed in ipsilateral
DRG of both groups. The number of IL-1β positive neurons, IL-1RI positive
neurons, IL-1β/IL-1RI double-stained neurons, and IL-1RI positive glia cells in
ipsilateral DRG of the AA group were higher than that of NS group (P<0.05 or P<
0.01). Conclusion: The coexsistence of IL-1β and IL-1RI in neurons and nonneuronal
cells suggests an as yet unknown autocrine and/or paracrine function of IL-1β in
the DRG. The function was enhanced in articular arthritis induced by CFA and
could play an important role in hyperalgesia under inflammatory conditions.