Association of myelinated primary afferents impairment with mechanical allodynia in diabetic peripheral neuropathy: an experimental study in rats

// Chenlong Liao 1 , Min Yang 1 , Wenxiang Zhong 1 , Pengfei Liu 1 and Wenchuan Zhang 1 1 Department of Neurosurgery, Xinhua Hospital Affiliated to Shanghai JiaoTong University School of Medicine, Shanghai, P. R. China Correspondence to: Wenchuan Zhang, email: zhangwenchuan@xinhuamed.com.cn Keywords: diabetic peripheral neuropathy, nerve decompression, mechanical allodynia, neuropathic pain Abbreviations: DPN: diabetic peripheral neuropathy; MA: mechanical allodynia; PWL: paw withdrawal latency; PWT: paw withdrawal threshold; STZ: streptozotocin Received: April 05, 2017 Accepted: June 16, 2017 Published: July 18, 2017 ABSTRACT To investigate the mechanisms underlying the efficacy of surgical treatment for painful diabetic peripheral neuropathy. Rats were initially divided into 3 groups (I, control rats, II, streptozotocin-induced diabetic rats, III, streptozotocin-induced diabetic rats with latex tube encircling the sciatic nerve without compression). When mechanical allodynia (MA) became stable in the third week, one third of group III rats were sacrificed and the remainder were further divided into subgroups depending on whether the latex tube was removed. Except for some rats in group III, all rats were sacrificed in the fifth week. Morphometric analysis of nerve fibers was performed. Expression level of GABA B receptor protein in spinal dorsal horn was determined. Changes of GABA B receptor within areas of primary afferents central terminal were identified. Chronic nerve compression caused by the interaction of diabetic nerves swelling and the encircling latex tube increased the incidence of MA in diabetic rats, and nerve decompression could ameliorate MA. In diabetic rats with MA, demyelination of myelinated fibers was noted and reduction of GABA B receptor was mainly detected in the area of myelinated afferent central terminals. MA in DPN should be partially attributed to compression impairment of myelinated afferents, supporting the rationale for surgical decompression.