ABSTRACT
Objective To evaluate the effects of regional seawater immersion on the pain behavior and its secondary neuropathological change in the rats model of skin/muscle incision and retraction (SMIR). Methods Forty-eight male SD rats were randomly assigned into 3 groups (16 each): the model control group (only to set up SMIR model, Group MC), normal saline immersion group (to set up SMIR model and the incision immersed with normal saline, Group NS), seawater immersion group (to set up SMIR model and the incision immersed with seawater, Group SW). Mechanical paw withdrawal threshold (MWT) was measured 1d before and 1d, 3d, 5d, 7d, 14d, 21d and 28d after operation, respectively. At 3d and 28d after the operation, 8 rats were randomly selected from each group, ipsilateral saphenous nerves were taken from 4 rats for HE staining, and dorsal root ganglion of ipsilateral L3/L4 were taken from another 4 rats for ultrastructural observation by electron microscopy. Results Compared with the other two groups, MWT values in Group SW significantly reduced at every observation time and remained significantly lower than the basic level at 28d. There were no differences in MWT values between Group MC and Group NS, and the MWT values of the two groups at 28d were comparable with preoperative basic level. The HE staining of Group SW showed saphenous nerves were injured, while of Group MC and Group NS were normal. A large number of vacuolar mitochondrion and autophagosomes were observed in dorsal root ganglion of Group SW and few swelling mitochondrion was found in the other two groups. Conclusions Regional seawater immersion can aggravate the pain evoked by SMIR and may result in chronic pain. Peripheral nerve injury, ultrastructure changes of dorsal root ganglion neurons in rats caused by regional seawater immersion may be involved in the mechanism of the change of pain behavior.
ABSTRACT
Objective: To observe the effect of preemptive local injection of ropivocaine with dexmedetomidine on activation of glial cells and on the mirror pain in rats and its mechanism. Methods: A total of 48 adult male Sprague-Dawley rats (weighing 180 g-220 g) were included in the study and randomized into 3 groups, Group S, Group R, and Group RD
ABSTRACT
OBJECTIVE@#To observe the effect of preemptive local injection of ropivocaine with dexmedetomidine on activation of glial cells and on the mirror pain in rats and its mechanism.@*METHODS@#A total of 48 adult male Sprague-Dawley rats (weighing 180 g-220 g) were included in the study and randomized into 3 groups, Group S, Group R, and Group RD1. A rat model of persistent postoperative pain evoked by skin/muscle incision and retraction was established in the three groups. Before procedures and nerve extraction, Group S (n = 16) was injected 0.9% saline locally; Group R (n = 16) was injected 0.5% ropivocaine locally, and Group RD1 (n = 16) was injected 0.5% ropivocaine in combined with 1 μg dexmedetomidine locally. After the model being established in the three groups, 8 rats were used for behavior test until 28 d, and dorsal root ganglions (DRGs) of the other 8 rats were harvested on the 3rd day after surgery. Immunofluorescent and transmission electron microscopy were used to observe the activation of glial cells in DRG, and the behavior test results in the three groups were compared.@*RESULTS@#The results showed that mechanical pain threshold in ipsilateral hind-paws of the Group S, Group R, Group RD1 animals dropped to (3.640 ± 1.963) g, (5.827 ± 1.204) g, (7.482) ± 1.412 g at 3 d respectively; while in contralateral paws dropped to (7.100 ± 1.789) g, (17.687 ± 1.112) g, (16.213 ± 1.345) g on the 3 d respectively. Immunofluorescent showed that the glial cells were activated in bilateral side DRG after surgery in 3 groups, but ipsilateral paws expressed more active glial cells than contralateral paws. Transmission electron microscopy showed that mitochondria swelling/vacuolization and lysosomes were more obvious in ipsilateral paws than contralateral paws, but Group RD1 formula could reduce glial cells activity, mitochondria swelling/vacuolization and the amount of lysosomes.@*CONCLUSIONS@#Local injection of ropivocaine and/or dexmedetomidine can effectively inhibit the activation of glial cells in DRG, mitigate the pathological changes of neuron in DRG and reduce mirror image pain.