Study On The Changes Of Motor Neurons In Ventral Horn And Axons In Spinal Cord After Radiation Induced Brachial Plexus Injury Of Rats

Radiation therapy is one of the most important methods to safely andeffectively treat various cancers. As a component of peripheral nerves, brachialplexus injury is a common complication during radiation therapy. With thedevelopment of treatment methods, the survival period of patients wassignificantly longer. The radiation induced brachial plexus injury (RIBPI) hasbeen paid more and more attention.Objective:In the present study, SD rats were radiated with divided-dose of radiation,which simulated the therapy protocol for breast cancer, to observe the changes ofmorphology and the changes of motor neurons in ventral horn in spinal cord,which were induced by radiation. Our experiments want to discover the rule ofradiation-induced injury of brachial plexus, and also if there exits the reversibleconversion in neurons.Methods:We established RIBPI animal models by divided-dose of radiation. The ratswere divided randomly into brachial plexus injury groups (experiment groups)and control group. Using 2 Gy/time, 5 times/week with a total administered doseof 30 Gy reached in 3 weeks, experiment groups were divided into different-timegroups after radiation as 3-week, 5-week, 7-week and 9-week group. There are 4rats in each time group and control group. In each time group, the left is theradiation side, the right is the control side. We draw the material in the differenttime after the last time radiation。Sample from the wet biceps brachii muscle of each arm were weighed andSamples off muscle were subsequently embed for immunohistochemistry (IHC)detection. The wet weights of biceps brachii muscle and upper-limbcircumference were evaluated as described previously. An compound actionpotential and its latent period were also evaluated。Using H-E staining, argentumsstaining and toluidine blue staining methods, we observed the pathologicalchanges of biceps brachii muscle, the morphological changes and counts of themotor neurons in ventral horn and axons of bilateral spinal cord. Meantime, theexpression of c-fos gene has been detected in motor neurons in ventral horn byICH methods.Results3 weeks after radiation, animals of experiment group begin to appearlameness on the side of radiation and a "claw hand".The wet weights of biceps brachii muscle and upper-limb circumference weresignificantly reduced (P <0.01or P <0.05) after radiation 3-week, 5-week, 7-weekand 9-week group. Compared with control side, biceps brachii muscle atrophy orasymmetry was seen in the radiation side of upper extremities with hematoxylinand eosin (HE) staining. Meanwhile, the compound action potential significantlydecreased, and its latent period was also significantly prolonged (P <0.01 or P<0.05). The compound action potential showed the lowest point, and its latentperiod was also the longest one 3 weeks after the last radiation administered, afterthat, all of them are recovered in some sort. The account of motor neurons inventral horn was significantly decreased in the radiation side with time extending(P <0.01), we also can observed the sign of cell death, such as, the neuronscrimple, and karyolysis. There was rapidly decrease of motor neurons in ventral...