Effects of naloxone hydrochloride on the expressions of CD11b/c and GFAP in the rat model of neuropathic pain

Objective To investigate the effects of naloxone hydrochloride on the expressions of CD11b/c and glial fibrillary acidic protein (GFAP) in the rat model of neuropathic pain, and analysis the possible mechanism of naloxone hydrochloride in the treatment of neuropathic pain. Methods A total of 60 SD rats were selected and divided into sham operation group (group S, n=12) and model group (n=48). Then the rats in the model group were randomly divided into 4 groups, namely, CCI group and naloxone hydrochloride P1, P2 and P3 groups, 12 cases in each group. While the sciatic nerve was exposed only in group S. Group P1, group P2 and group P3 received subcutaneous injection of naloxone 1 mg·kg-1, 10 mg·kg-1, 100 mg·kg-1 respectively, 1 time/d, continuous 7 d. Group S and group CCI were given equal volume of normal saline. The behavior of rats in each group was observed, and the mechanical pain threshold (MWT) and thermal pain threshold (PWTL) of rats before and 1, 3, 5 and 7 d after administration were measured. Immunohistochemistry was used to detect the changes of CD11b/c and GFAP in the spinal dorsal horn of L4~5. Results Compared with group S, MWT and PWTL were significantly decreased in CCI group (P<0.05). Compared with CCI group, MWT, PWTL were significantly increased with time-dependently and dose-dependently of rats in group P1(P<0.05), which was began to obviously increase in group P1 at the third day, P2 and P3 at the first day after administration respectively (P<0.05). After administration of the 7th day, compared with group S, the average optical density of CD11b/c and GFAP in group CCI was significantly increased (P<0.05). Compared with group CCI, the average optical density of CD11b/c and GFAP was decreased significantly with a dose-dependent manner in group P1, P2 and P3 (P<0.05). Conclusion Naloxone hydrochloride can alleviate neuropathic pain in CCI rats, suggesting that the mechanism may be to inhibit the expression of CD11b/c and GFAP in the spinal dorsal horn. Key words: Naloxone; CD11b/c; Glial fibrillary acidic protein; Neuropathic pain