脂质体包裹对布比卡因致大鼠脊髓神经毒性的影响

Effect of encapsulation in liposomes on toxic effect of bupivacaine on spinal cord in rats

目的评价脂质体包裹对布比卡因致大鼠脊髓神经毒性的影响。方法取鞘内置管成功的sD大鼠108只，体重200—225g，采用随机数字表法，将其随机分为6组（n=18）：对照组（c组）、脂质体组（L组）、0．5％布比卡因组（B1组）、1％布比卡因组（B2组）、0．5％脂质体布比卡因组（LB1组）和1％脂质体布比卡因组（LB2组）。从鞘内置管成功第4天开始，L组、B，组、B2组、LB1组和LB2组每天分别鞘内注射脂质体、0．5％布比卡因、1％布比卡因、0．5％脂质体布比卡因和1％脂质体布比卡因各20μl，连续7d。给药结束后观察大鼠后肢形态和行走状况。采用痛敏仪测定大鼠后爪机械痛阈。痛阈测定结束后每组随机处死8只大鼠，取腰膨大处脊髓组织，采用免疫组化法计数Fos蛋白阳性细胞。痛阚测定结束后每组随机处死8只大鼠，取注射节段脊髓组织，采用流式细胞仪测定细胞凋亡情况，计算细胞凋亡率。痛阈测定结束后每组随机取2只大鼠，取L3-4节段脊髓组织，观察神经元超微结构。结果与c组比较，L组机械痛阈、Fos蛋白阳性细胞计数和细胞凋亡率差异无统计学意义（P〉0．05），B1组和LB1组Fos蛋白阳性细胞计数升高（P〈0．01），机械痛阈和细胞凋亡率差异无统计学意义（P〉0．05），B2组机械痛阈、Fos蛋白阳性细胞计数和细胞凋亡率升高，LB2组Fos蛋白阳性细胞计数和细胞凋亡率升高（P〈0．01），机械痛阈差异无统计学意义（P〉0．05）；与B1组比较，LB2组机械痛阈和细胞凋亡率差异无统计学意义（P〉0．05），Fos蛋白阳性细胞计数降低，B：组机械痛阈、Fos蛋白阳性细胞计数和细胞凋亡率升高（P〈0．01）；与B2组比较，LB2组机械痛阈、Fos蛋白阳性细胞计数和细胞凋亡率降低（P〈0．01）；与LB1组比较，LB2组机械痛阈差异无统计学意义（P〉O．05），Fos蛋白阳性细胞计数和细胞凋亡率升高（P〈0．01）。结论脂质体包裹可减轻鞘内注射1％布比卡因对大鼠脊髓的神经毒性。

Objective To study the toxic effect of bupivacaine encapsulated in liposomes on spinal cord in rats. Methods One hundred and eight SD rats （200-225 g） in which intrathecal （IT） catheter was successfully implanted without complications were randomly divided into 6 groups （ n = 18 each） ： control group （group C） ; liposome group （group L） ; 0.5% and 1.0% bupivacaine groups （groups B1 and B2 ） and 0.5% and 1.0% bupivacaine encapsulated in liposomes groups （groups LBl and LB2 ）. In groups L, BI , B2, LB1 and LB2, liposome, 0.5 % bupivacaine, 1.0 % bupivacaine,0.5 % liposomal bypivacaine and 1.0 % liposomal bupivacaine 20 tzl were injected IT respectively once a day for 7 consecutive days, while in group C nothing was injected IT. Pain thresh- old was measured by mechanical stimulation of the plantar surface of hindpaw. Motor function of the hindlimbs was also assessed. The animals were sacrificed at 8 day after IT injection. The lumbar segment of the spinal cord was removed for microscopic examination, detection of neuronal apoptosis （by flow cytometry） and Fos protein expres- sion （by immuno-histochemistry）. Results 1.0 % bupivacaine IT significantly increased the percentage of apoptot- ic neurons in group Bz as compared with control group. 0.5 % and 1.0 % bupivacaine IT significantly increased the number Fos protein positive ceils in group Bl and B2 as compared with group C. 1.0% bupivacaine IT induced se- vere histologic damage including shrinkage of nucleus and vacuole formation in mitochondria. Encapsulation of bupivacaine in liposomes significantly attenuated bupivacaine-induced increase in apoptosis and Fos protein expression and histologic damage in group LB2 as compared with group B2 . Conclusion The encapsulation in liposomes can decrease the neurotoxicity of 1.0 % bupivacaine administered IT in rats.