Tanabe Mitsuo, Shimizu Shinobu, Takabayashi Katsuya, Honda Motoko, Ono Hideki
Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan.
Neurosci Lett. 2005 Dec 9;389(3):152-6. doi: 10.1016/j.neulet.2005.07.039.
Diabetes is frequently accompanied by painful polyneuropathies that are mediated by enhanced neuronal excitability in the spinal cord, partly because of decrease in spinal intrinsic inhibitory influences. Changes in spinal excitatory-inhibitory balance may alter spinal segmental motor output. In the study presented here, the mono- and disynaptic (the fastest polysynaptic) reflexes (MSR and DSR, respectively) were recorded from L5 ventral roots in response to stimulation of the ipsilateral L5 dorsal root in spinalized streptozotocin (STZ)-induced diabetic rats with a reduced withdrawal threshold to mechanical stimuli. The diabetic rats generally exhibited larger spinal reflex amplitudes, the DSR being influenced in particular. We addressed whether recurrent and presynaptic inhibition of the spinal reflexes were altered in STZ-treated animals. The recurrent inhibition of the MSR and DSR elicited by preceding antidromic conditioning stimulation delivered to the recorded L5 ventral root was markedly suppressed in diabetic rats. By contrast, the presynaptic inhibition of the MSR and DSR elicited by preceding conditioning stimulation to the ipsilateral L4 dorsal root was not impaired. Thus, in diabetic painful neuropathy, reduced spinal intrinsic inhibition in the ventral horn contributes to an enhanced spinal segmental motor output.
糖尿病常伴有疼痛性多发性神经病变，其部分原因是脊髓中神经元兴奋性增强，这是由于脊髓内在抑制作用减弱所致。脊髓兴奋性 - 抑制平衡的改变可能会改变脊髓节段性运动输出。在本研究中，在脊髓横断的链脲佐菌素（STZ）诱导的糖尿病大鼠中，记录L5腹根对同侧L5背根刺激的单突触和双突触（最快的多突触）反射（分别为MSR和DSR），这些大鼠对机械刺激的撤腿阈值降低。糖尿病大鼠通常表现出更大的脊髓反射幅度，尤其是DSR受到影响。我们研究了STZ处理的动物中脊髓反射的回返性抑制和突触前抑制是否发生改变。在糖尿病大鼠中，通过向记录的L5腹根传递先前的逆向条件刺激所引发的MSR和DSR的回返性抑制明显受到抑制。相比之下，通过对同侧L4背根进行先前的条件刺激所引发的MSR和DSR的突触前抑制并未受损。因此，在糖尿病性疼痛性神经病变中，腹角脊髓内在抑制的降低导致脊髓节段性运动输出增强。
