RESUMEN
Peripheral nerve injury can cause changes in microglial cells on the spinal dorsal and ventral horns. This region-specific response implies that central microglial cells could be activated through both sensory and motor pathways. In order to further determine how peripheral nerve injury activates central microglial cells through neural pathways, the sciatic nerve was selected as the target for neural tract tracing and demyelination. Firstly, we used cholera toxin subunit B (CTB) to map the central sensory and motor territories of the sciatic nerve. Secondly, we applied lysophosphatidylcholine to establish the model of sciatic nerve demyelination and examined the distribution of activated microglial cells via immunofluorescence with ionized calcium-binding adapter molecule 1. It was shown that CTB labeling included the transganglionically labeled sensory afferents and retrogradely labeled somata of motor neurons along the sensory and motor pathways of the sciatic nerve ipsilateral to the injection, in which sensory afferents terminated on the gracile nucleus, Clarke's nucleus, and spinal dorsal horn, while motor neurons located on the spinal ventral horn. Consistently, after sciatic axon demyelination, the activated microglial cells were observed in the same territories as CTB-labeling, showing shortened processes and enlarged cell bodies. These results support the idea that central microglia might be activated by signals from the demyelinated sciatic nerve through both sensory and motor pathways.
RESUMEN
OBJECTIVE: To observe the effect of electroacupuncture(EA) on the pain behavior and prostaglandin E2 (PGE2), calcitonin gene-related peptide (CGRP) and substance P (SP) in the spinal cord dorsal horn and dorsal root ganglia (DRG) of rats with knee osteoarthritis (KOA), so as to explore the mechanisms of EA underlying improvement of chronic pain in KOA rats. METHODS: Thirty-two female SD rats were randomly divided into blank group, control group, model group and EA group, with 8 rats in each group. Rats in the control group were injected with 50 µL of 0.9% sodium chloride solution into the left knee joint cavity, and rats in the model and EA groups were injected with 50 µL of Monosodium iodoacetate in the left knee joint. EA(2 Hz/100 Hz, ï¼2 mA) was applied to left "Yanglingquan"(GB34) and "Neixiyan" (EX-LE4) for 15 min, once daily, 5 days a course with a total of 2 courses. Paw withdrawal latency (PWL) and mechanical pain threshold (PWT) were tested by Plantar Test and Von Frey, separately. After the last pain test, the contents of PGE2, CGRP and SP in the left lumbar (L) 3-L5 DRG and L3-L5 spinal dorsal horn were detected by ELISA. RESULTS: Compared with the blank group, the PWL and PWT of the rats in the model group were significantly decreased (P<0.01), and the contents of PGE2, CGRP and SP in the DRG and spinal dorsal horn were significantly increased (P<0.01, P<0.05). There were no statistically significant differences in PWL, PWT, contents of PGE2, CGRP and SP in DRG and spinal dorsal horn between the blank group and the control group (P>0.05). Compared with the model group, the PWL and PWT of rats in the EA group were significantly increased (P<0.01), and the contents of PGE2, CGRP and SP in the DRG and spinal dorsal horn were significantly decreased (P<0.01, P<0.05). CONCLUSION: EA of GB34 and EX-LE4 can reduce the levels of pain-related factors PGE2, CGRP and SP in the DRG and spinal dorsal horn, thereby relieving spinal hyperalgesia in rats with KOA.
