Pain MechanismOcular surface-evoked Fos-like immunoreactivity is enhanced in trigeminal subnucleus caudalis by prior exposure to endotoxin
Section snippets
Experimental procedures
The experimental protocols were approved by the Institutional Animal Care and Use Committee of the University of Minnesota and conformed to the established guidelines set by the National Institutes of Health guide for the care and use of laboratory animals (Publications No. 99–158, revised 2002). All efforts were made to minimize the number of animals used for experiments and their suffering.
General effects of LPS
Naïve rats gained 6.1±1.3% and 21.5±5.4% of initial body weight by 2 and 7 days, respectively, over the course of the experimental period. Rats given systemic LPS had minor weight loss at 2 days (−3.3±1.5%, P>0.05) and a significant gain at 7 days (7.7±2.2%, P<0.01) compared with naïve rats. Rats given ivt injections of LPS also had minor weight loss by 2 days (0.3±0.8%, P>0.05) and gained weight at 7 days (5.3±2.7%, P<0.05) compared with naïve rats. By contrast, rats given i.c.v. LPS rats lost
Discussion
The main finding of this study was that systemic or intraocular administration of LPS enhanced Fos-LI expression in multiple TSNC regions after noxious chemical stimulation of the ocular surface in a time-dependent manner, while intracerebral LPS had only minor effects. Noxious sensory stimulation of the ocular surface by MO significantly increased Fos-LI in the ViVcvl transition and Vc/C1–2 junction regions, responses that were further enhanced by 7 days, but not 2 days, after systemic or
Acknowledgments
This was supported by NIH grant NS26137. The authors wish to thank J. Cioffi for excellent technical assistance.
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2017, Ocular SurfaceCitation Excerpt :Central sensitization can develop in the setting of ongoing afferent nociceptive traffic that occurs with peripheral sensitization [390,391]. Anatomically, corneal nociceptors have their cell bodies in the TG and synapse in two main areas of the TBNC, the ViVc transition and the spinomedullary junction or the Vc/C1-2 region [100,392,393]. Dry-responsive neurons have been identified in the ViVc transition, and a subgroup of these neurons receive additional converging input from corneal afferents sensitive to other stimuli such as acidity, heat and noxious chemicals [100,190].
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