• Yasuhito Motojima, Takanori Matsuura, Mitsuhiro Yoshimura, Hirofumi Hashimoto, Reiko Saito, Hiromichi Ueno, Takashi Maruyama, Satomi Sonoda, Hitoshi Suzuki, Makoto Kawasaki, Hideo Ohnishi, Akinori Sakai, and Yoichi Ueta.
• Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan; Department of Orthopaedic Surgery, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
• Neuroscience. 2017 Jul 25; 356: 64-77.

AbstractWe evaluated whether a c-fos-enhanced green fluorescent protein (eGFP) transgenic rat line, which expresses the c-fos and eGFP fusion gene, can be useful for the study of nociceptive pathways and processing. Capsaicin solution (15%) or formalin (5%) was subcutaneously injected bilaterally into the hind paws (100μL per each paw) of adult male c-fos-eGFP transgenic or wild-type rats. Control rats were injected with ethanol or physiological saline respectively. Transgenic and wild-type rats were perfused at 1.5, 3 and 6h post injection, with some transgenic rats being perfused 24h post injection. A comparison of eGFP in transgenic rats and Fos-like immunoreactivity (LI) in wild-type rats was made in the dorsal spinal cord, paraventricular nucleus (PVN) and supraoptic nucleus (SON). Oxytocin-LI (OXT-LI) was carried out to examine the activation of OXT neurons in the PVN and SON. Following capsaicin or formalin treatment, eGFP was maximally expressed at 6h in the spinal cord and 3h in the PVN and SON, whereas, Fos-LI was maximally expressed at 1.5h in all the regions we analyzed. Induction of eGFP in the OXT neurons was observed after capsaicin or formalin treatment, while Fos-LI in the OXT neurons was observed only after formalin treatment. These results demonstrate that the peak induction of c-fos-eGFP following exposure to acute nociceptive stimuli was delayed by around 1.5-4.5h, but more sensitive than endogenous Fos, suggesting that the c-fos-eGFP rat line can be useful for the study of nociceptive pathways and processing.Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

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