The Effects Of Hyperbaric Oxygen And Shen-Fu Injection On Neuropathic Pain In Rats

Partâ… The effects of hyperbaric oxygen on neuropathic pain in ratsExperiment 1 The effects of early HBO treatment on the development of neuropathic pain in CCI ratsBackground Neuropathic pain affects approximately 0.6% to 1.5 % of the total US population. However, the current available therapies offer substantial pain relief to less than half of the affected patients. Hyperbaric oxygen (HBO) has been suggested to be beneficial in various diseases including neuronal ischemic injury and also improves the nerve regeneration. Objective The current study was designed to investigate whether early HBO treatment could prevent the development of neuropathic pain in CCI rats. Methods Eighty-four male SD rats were divided into 7 groups randomly as follows (n =12 in each group): CCI group in which the rats underwent the CCI (the sciatic nerve chronic constriction injury) procedure; HBA group in which the rats were exposed to Hyperbaric air (HBA) with 21% oxygen at 3.0 atmosphere absolute once daily for 7 consecutive days at 4 hours after the CCI procedure; O2 group in which the rats were exposed to normal-baric oxygen with 100% oxygen at 1.0 atmosphere absolute (ATA) once daily for 7 consecutive days at 4 hours after the CCI procedure; HBOA ,HBOB and HBOC groups in which the rats were exposed to HBO with 100% oxygen at 1.5 , 2.0 and 3.0 ATA respectively once daily for 7 consecutive days at 4 hours after the CCI procedure; and Sham group in which the rats underwent the same procedure as HBOC group but without ligature of the sciatic nerve. At 2, 3, 7, 10, 14, 21, 28, 35, 42, 49 and 56 days after the surgery, the time course of hyperalgesia including thermal paw withdrawal latency and Von Frey withdrawal threshold were examined. Resultsâ‘ There were significant changes in the mechanical withdrawal thresholds and thermal paw withdrawal latencies of the feet ipsilateral to injury between sham group, CCI group and HBOC group (RM ANOVA by post hoc LSD,P<0.01). The mechanical withdrawal thresholds of HBOC group were significantly lower than those in sham group on all postoperative days, but significantly higher than those in CCI group (RM ANOVA by post hoc LSD,P<0.01). On the other hand, the thermal paw withdrawal latencies of HBOC group were significantly higher than those in CCI group on all postoperative days (RM ANOVA by post hoc LSD,P<0.01). Compared with sham group, the thermal withdrawal latencies of HBOC group decreased significantly on 3^rd, 7^th, 10^th, and 14^th postoperative days (One-way ANOVA,P<0.01), but there were no significance changes since 21th postoperative day.â‘¡There were significant changes in the mechanical withdrawal thresholds and thermal paw withdrawal latencies between HBA group, O2 group and HBOC group (RM ANOVA by post hoc LSD,P<0.01). The mechanical withdrawal thresholds and thermal paw withdrawal latencies of HBOC group were significantly higher than those in HBA group and O2 group on all postoperative days.â‘¢There were significant changes in the mechanical withdrawal thresholds and thermal paw withdrawal latencies between HBOA group, HBOB group and HBOC group (RM ANOVA by post hoc LSD,P<0.01). The mechanical withdrawal thresholds and thermal paw withdrawal latencies of HBOC group were significantly higher than those in HBOA group and HBOB group on all postoperative days. Conclusions Early HBO treatment (100% oxygen at 3.0 ATA but not 1.5 or 2.0ATA)once daily for 7 consecutive days at 4 hours after the CCI surgery prevents the development of thermal hyperalgesia and significantly attenuates the mechanical allodynia in CCI rats. Both hyperbaric and hyper-oxygen element contributed to the analgesia effects of early HBO treatment. Single use of either hyperbaric or hyper-oxygen element had little effect on neuropathic pain in CCI rats. HBO treatment with 100% oxygen at 3.0 atmospheres absolute is the optimal protocol for the treatment of neuropathic pain.Experiment 2 The effects of delayed HBO treatment on the maintenance of neuropathic pain in CCI ratsObjective The present study was designed to examine the effects of delayed HBO treatment on the maintenance of neuropathic pain in CCI rats. Methods The neuropathic pain rats induced by CCI were randomly divided into two groups as follows: CCI group (n =9) in which the rats underwent the CCI procedure; HBO group (n =10) in which the rats were exposed to HBO with 100% oxygen at 3.0 ATA once daily for 3 consecutive days at 14 days after the surgery. At 2, 7, 14, 17, 21, 24 and 28 days after the surgery, the time course of hyperalgesia were examined. Results There were significant changes in the mechanical withdrawal thresholds and thermal paw withdrawal latencies of the feet ipsilateral to injury between CCI group and HBOT group (RM ANOVA by post hoc LSD,P<0.01). At 17, 21 and 24 days after the surgery, the scores of thermal paw withdrawal latency and mechanical withdrawal threshold in HBOT group were significantly higher than those in CCI group (One-way ANOVA, P<0.01). Conclusion Delayed HBO treatment (100% oxygen at 3.0 ATA) once daily for 3 consecutive days started at 14 days after the CCI surgery significantly reduced thermal and mechanical hyperalgesia in the neuropathic pain rats induced by CCI surgery. Moreover, the inhibitory effect can last for 7 days after termination of the HBO treatment.Experiment 3 The effects of HBO preconditioning on the development of neuropathic pain in CCI ratsObjective To investigate whether HBO preconditioning could postpone the development of neuropathic pain in CCI rats. Methods Twenty-four SD rats were divided into three groups randomly as follows (n =8 in each group) :â‘ CCI group in which the rats underwent the CCI procedure;â‘¡HBOp group in which the rats were exposed to HBO with 100% oxygen at 3.0 ATA once daily for 7 consecutive days. At 24h after last precondition, the rats were subjected to CCI surgery.â‘¢Sham group in which the rats were underwent the same procedure as HBOp group but without ligature of the sciatic nerve. At -8, -1, 3, 7, 10 and 14days after the surgery, the time course of thermal paw withdrawal latency were examined. Results There were significant changes in thermal paw withdrawal latencies of the feet ipsilateral to injury between sham group, CCI group and HBOp group (RM ANOVA by post hoc LSD, P<0.01). At 3, 7, 10 and 14 days after the surgery, the scores of thermal paw withdrawal latency in HBOp group were significantly lower than those in sham group, however, the scores of thermal paw withdrawal latency in HBOp group were significantly higher than those in CCI group at 3rd and 7th postoperative days(One-way ANOVA, P < 0.01 ) . Conclusion HBO preconditioning postpones the development of thermal hyperalgesia in CCI rats.Partâ…¡The effects of Shen-Fu injection on the development of neuropathic pain in CCI ratsObjective To investigate whether Shen-Fu injection, an intravenous drug made from traditional Chinese medicinal herbs, could postpone the development of neuropathic pain in CCI rats. Methods Thirty-two SD rats were divided into four groups randomly as follows(n =8 in each group):â‘ CCI group in which the rats underwent the CCI (the sciatic nerve Chronic constriction injury) procedure;â‘¡CCI+ saline group in which the rats were injected with saline(25ML/kg) once daily for 7 consecutive days immediately after the CCI procedure;â‘¢CCI+ ShenFu group in which the rats were injected with ShenFu injection(25ML/kg) once daily for 7 consecutive days immediately after the CCI procedure; andâ‘£Sham group in which the rats underwent the same procedure as CCI group but without ligature of the sciatic nerve. At -2, 1, 3, 7, 10 and 14 days after the surgery, the time course of hyperalgesia including thermal paw withdrawal latency and mechanical withdrawal threshold were examined. Results Compared with Sham group, the scores of thermal paw withdrawal latency and mechanical threshold in the CCI group and CCI+saline group decreased significantly after the surgery (P< 0.01). The scores of mechanical withdrawal threshold in these two groups declined from the first day, and eventually reached the bottom at the 7th day after the surgery. The scores of thermal paw withdrawal latencie in these two groups were significantly lower than the scores in Sham group from the first day after the surgery, and reached the bottom at 3rd day after the surgery. There was no significant difference in thermal paw withdrawal latencies and mechanical withdrawal thresholds between CCI group and CCI+saline group. At 1,3, 7 days after the surgery, the scores of mechanical withdrawal threshold in CCI+Shenfu group were significantly higher than those in CCI and CCI+saline group (P<0.05). However, there was no significant difference in thermal paw withdrawal latencies and mechanical withdrawal thresholds since the 10th after the surgery. Compared with CCI and CCI+saline group, the scores of thermal paw withdrawal latency in CCI+Shenfu group were only higher than those in CCI and CCI+saline group on the 1st after CCI surgery (P<0.05), significantly. Conclusion Early Shen-Fu injection treatment once daily for 7 consecutive days immediately after the CCI surgery could mildly postpone the development of mechanical hyperalgesia induced by CCI surgery, but only reduced thermal hyperalgesia at the 1st day after the surgery.Summary:1. Early HBO treatment (100% oxygen at 3.0 ATA but not 1.5 or 2.0ATA)once daily for 7 consecutive days at 4 hours after the CCI surgery prevents the development of thermal hyperalgesia and significantly attenuates the mechanical allodynia in CCI rats. Both hyperbaric and hyper-oxygen element contributed to the analgesia effects of early HBO treatment. Single use of either hyperbaric or hyper-oxygen element had little effect on neuropathic pain in CCI rats. HBO treatment with 100% oxygen at 3.0 atmospheres absolute is the optimal protocol for the treatment of neuropathic pain.2. Delayed HBO treatment (100% oxygen at 3.0 ATA) once daily for 3 consecutive days at 14 days after the CCI surgery could reduced thermal and mechanical hyperalgesia in the neuropathic pain rats induced by CCI surgery significantly. Moreover, the inhibitory effect can last for 7 days after termination of the HBO treatment.3. HBO preconditioning postpones the development of thermal hyperalgesia in CCI rats.4. Early Shen-Fu injection treatment once daily for 7 consecutive days immediately after the CCI surgery could mildly postpone the development of mechanical hyperalgesia induced by CCI surgery, but only reduced thermal hyperalgesia at the 1st day after the surgery.