| Objective To establish a compressing model of rat dorsal root ganglion neurons in vitro and observe the changes in appearance and activity in cultured rat dorsal root ganglion (DRG) neurons under constant pressure(80mmHg)and different time intervals, then made modest evaluation about the advantages and disadvantages of the neuron culture model.Methods According to the pressure exerting time, the cultured DRG cells was assigned to three groups: 24h group, 48h group and normal control group, the changes of appearance and activity were demonstrated by fluorescent microscope,transmission electron microscopy and MTT assay.Results There was no significant difference among groups under fluorescent microscope. In the 24h group and 48h group, compared with control group, the electron microscopy results of ultra-structure suggested that being cultured in the high-pressure environment would influence the metabolism of neurons: the number of the rough endoplasmic reticulum decreased, and its length was shorten, mitochondrion swelled and some nucleolus concentrated, electron microscope also showed the increment of free ribosome et al. No significant activity changes was detected by MTT method among groups (P>0.05).Conclusion The novel compressing model of DRG neuron could avoid the defect of models in vivo, we have the convenience to observe the function of single pressure factor exactly, the model would provide an effective tool for the studies of the effect of mechanical compression towards DRG neurons. Objective To investigate the changes of neuroethology and morphology of the dorsal root ganglion (DRG) after chronic compression. Then the expression of TRPV4 in the chronically compressed dorsal root ganglion was studied among different groups, to explore the function of TRPV4 channel in the process of chronic compression toward DRG.Methods 63 adult, male Wistar rats were randomly classified into seven groups, of which 9 were unoperated control group, 27 were experiment model group and the rest 27 were sham-operation group. In the experiment model group, a U shape stainless rod was inserted into the right intervertebral foramina of the lumber 4 and 5. The sham-operation group's surgical procedure was identical to that of the experiment model group but without injury to the dorsal root ganglion, and no operation was performed to the unoperated control group. First, the motor function and mechanostimulation pain threshold in the affected hind limb of the rats were studied on 1st, 3rd, 7th, 9th, 11th, 13th, 15th, 17th, 19th, 21th, 23th, 25th and 27th after injury. Next, we observed the dorsal root ganglions under optical microscope after 7d, 14d and 28d respectively. Finally, the expression alteration of the TRPV4 protein in dorsal root ganglions was analyzed by Western-Blotting.Results The experiment model group presented significant hyperalgesia behavior after injury, as compared with those in the sham-operation group. On post-injury 7 days and 14 days groups, there were obvious hyperemia,edema and inflammation in the dorsal root ganglions. On post-injury 28 days group, the degree of hyperemia and edema decreased, but the proliferation of fibrocyte in the epineurium and endoneurium was observed. None of the phenomena was observed in the unoperated control group and sham-operation group. Compared with the unoperated control group and sham-operation group, the expression level of TRPV4 in the experiment model group was significantly increased at 7 days, 14 days and 28 days.Conclusion There were marked hyperalgesia behaviors in rats after chronic compression on the dorsal root ganglions. Pathological changes of neuron and nerve such as hyperemia,edema,inflammation and the proliferation of fibrocyte of neuron and nerve could be observed in the model group. At the same time, the expression of TRPV4 channel was increased correspondingly. These data suggests that TRPV4 channel may play an important role in the development of pain during the chronic compression of DRG.
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