Neurotoxic effects of intrathecal ropivacaine on spinal cord in rats

Abstract

Objective To evaluate the neurotoxic effects of intrathecal (IT) ropivacaine on the spinal cord in rats.Methods Sixty healthy male SD rats weighing 180-220 g in which IT catheters were successfully placed according to Yaksh TL were randomly divided into 6 groups (n = 10 each). The animals received 0.75% bupivacaine 17 μl (group A1); 0.75% ropivacaine 20 μl (group A2)and 1% ropivacaine 15 HI (group A3 ) IT respectively. The volumes of IT bupivacaine/ropivacaine were doubled in group B : 075 % bupivacaine 34 μl(group B1); 0.75% ropivacaine 40 μl (group B2) and 1% ropivecaine 30 μl (group B3). The onset time of bilateral hindlimb paralysis and recovery time were recorded. The animals were killed at 6 h after IT bupivecaine/ropivacaine injection. The lumbar segment of the spinal cord was removed for microscopic examination with electron microscope and determination of expression of c-los mRNA (by RT-PCR) and protein (by immuno-histochemistry) .Results The onset time of hindlimb paralysis was shorter in group A3 and B1 and the number of los-protein positive cells and the expression of los-protein were significantly higher in. group B1 than in group A1.The onset time of hindlimb paralysis was shorter in group A3 and B2 and the number of los-protein positive cells and the expression of fos-protein were significantly higher in group B2 than in group A2. The onset time of paralysis was shorter, the rate of recovery of motor function of bilateral hindlimbs was lower, the number of fos-protein positive cells and expression of los-protein and mRNA were significantly higher and spinal cord injury was severer in group B2 than in group A3, B1 and B2. Conclusion 0.75 % and small dose of 1% ropivacaine administered 1T do not produce neurotoxicity to the spinal cord while large dose of 1% ropivecaine can produce neurotoxicity which is less severe than that produced by large dose of 0.75 % bupivacaine. Key words: Amides; Drug toxicity; Injections,spinal