Early Systemic Administration of IL-10 Inhibits Neuropathic Pain in Adult Rats with Tibial Nerve Injury

Objective To determine the effect of early systemic administration of IL-10 on peripheral neuropathic pain induced by tibial nerve permanent transection 〔modified spared nerve injury (mSNI)〕 in adult rats. Methods Male adult Sprague-Dawley (SD) rats (ten-week old, 250-300 g) with mSNI were randomly divided into mSNI, sham-operated, IL-10 intervention (intraperitoneal injection), PBS intervention (intraperitoneal injection) groups, each containing six rats. Intraperitoneally injections (IL-10 or PBS) were given immediately after surgeries for a single regime with a dosage of 500 μL (0.1 mg/mL). Plantar test, von Frey hairs test, pinprick test and acetone test were performed before and after tibial nerve injuries (0 d, 4/5 d, 7/8 d, 14/15 d) to evaluate region-specific pain responses of the rats on the plantar sural and saphenous skin territories of ipsilateral and contralateral hindpaws. The hindpaw position (on 8 d) of six additional rats with standard SNI was compared with those with mSNI. Results The rats with standard SNI showed an eversion posture of hindpaws, more prominent than those with mSNI. Region-specific pathological pain evoked by mechanical and thermal stimuli on the sural and saphenous skin territories of the plantar surfaces of rat hindpaws was demonstrated on the ipsilateral rather than contralateral hindpaws. This effect was shown in the rats with mSNI but not in those with sham operations. Compared with PBS, early intraperitoneal injection of IL-10 significantly and persistently attenuated either allodynia or hyperalgesia in the rats with mSNI. Conclusion Tibial nerve permanent transection models of adult rats can be used as a simple but useful rodent model of peripheral neuropathic pain. Early systemic administration of IL-10 impairs the pathogenesis of neuropathic pain induced by tibial nerve injuries.