Pain mechanismThe effect of site and type of nerve injury on the expression of brain-derived neurotrophic factor in the dorsal root ganglion and on neuropathic pain behavior
Section snippets
Animals
A total of 40 male Sprague–Dawley rats weighing 200–250g were used. All animal experimental procedures were approved by the Hyogo College of Medicine Committee on Animal Research and were carried out in accordance with the guidelines of the National Institutes of Health on animal care. Every effort was undertaken to minimize the number of animals used and their discomfort.
Surgical procedures
All experimental procedures were performed on rats that were deeply anesthetized with sodium pentobarbital (50mg/kg body
Neuropathic pain behavior
The time course of mechanical allodynia and heat hyperalgesia in the sham, DR, DR+VR, VR and SNT groups of rats is shown in Fig. 2 (n=8 in each group). Before surgery, rats rarely withdrew their paws from the innocuous mechanical stimuli applied to the plantar surface of the hind paw. Rats in the sham, DR and DR+VR groups did not show a significant change in response frequency (Fig. 2A, C and E, respectively). In contrast, most rats in the VR and SNT groups developed mechanical allodynia to
Discussion
The present study demonstrated the following new findings: (1) Rats in the L5 DR and DR+VR groups did not show both pain behaviors at 7 days after surgery, despite BDNF upregulation in medium- and large-size neurons in the L5 DRG. (2) L5 SNT, but not DR, DR+VR or VR, increased the expression of BDNF in the L4 DRG at 7 days after surgery.
Acknowledgments
This work was supported in part by grants-in-aid for scientific research and a grant from the Open Research Center, Hyogo College of Medicine, from the Japanese Ministry of Education, Science, and Culture. This work was also supported by grant-in-aid for Researchers, Hyogo College of Medicine. We thank Yuki Obata and Nobumasa Ushio for technical assistance. We thank Dr. D. A. Thomas for correcting the English usage.
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