Effects Of Different Level Of Cervical Sympathetic Block On Serum TNF-α, IL-1β And IL-8 Concentration In Formalin Test In Rabbit

Objective:The present study has investigated the role of stellate ganglion block(SGB) and cervical sympathetic block(CSB) in the local inflammatory pain induced by subcutaneous injection of formalin in rabbit's forelimbs and its mechanism.Methods: Thirty-six male rabbits were randomly divided into six groups: Ss group, Ts group, Cs group, Sc group, Tc group, Cc group. SGB and CSB were used to treat the local inflammatory pain induced by subcutaneous injection of formalin in rabbit's forelimbs. Ipsilateral eyelid droop (ptosis) and cervical sympathetic nerve stained with methylene blue at the autopsy were observed in all animals. Nociceptive behavior was observed for one hour using weighted pain score. The concentrations of serum TNF-α,IL-1βand IL-8 were detected at 10 min before the formalin/saline injection, 10, 60 and 120 min after the injection using Enzyme-Linked Immunosorbent Assay (ELISA).Results: (1) Ipsilateral eyelid droop was observed in the animals of Ts group, Tc group. The range stained with methylene blue was not significantly different in all animals. (2) The nociceptive responses to formalin in rabbits were biphasic. The early phase of nociceptive responses was not affected significantly in the animals of Ts group, Tc group. In contrast, the late phase of nociceptive responses was in part reduced in the animals of Ts group, Tc group. However, Ts group did not differ significantly from Tc group in the reductions of the late phase of nociceptive responses. (3) The concentrations of serum TNF-α,IL-1βand IL-8 increased significantly in formalin injection compared to saline injection. The concentrations of the above three cytokines were significantly reduced in the animals of Ts group, Tc group. However, Ts group did not differ significantly from Tc group in the reductions of the above three cytokines concentrations.Conclusions: The present study suggests that there is an antinociceptive effect of both SGB and CSB in formalin test. The antinociceptive effect seems to be associated with a reduction of the concentrations of serum pro-inflammatory cytokines.