Pain mechanismTransient receptor potential vanilloid 1-immunopositive neurons in the mouse are more prevalent within colon afferents compared to skin and muscle afferents
Section snippets
Animals
Experiments were performed on eight-week old male C57Bl/6 mice (Charles River, Wilmington, MA, USA) housed in the Department of Laboratory Animal Resources at the University of Pittsburgh Medical Center. All research performed conformed to NIH guidelines in accordance with the guidelines specified by the University of Pittsburgh Medical Center Animal Care and Use Protocols. All mice received water and food ad libitum. Special care was taken to minimize the number of mice used for this study and
Results
The retrograde tracers used in this study were chosen based on their ability to label nociceptive afferents with respect to their target tissues. Visceral afferents were retrogradely labeled by injecting Alexa Fluor-conjugated CTB into the subserosal space of the distal colon (n=9). CTB has been shown to retrogradely label visceral afferents more efficiently than either WGA or IB4 (Wang et al., 1998b). Alexa Fluor-conjugated WGA or IB4 was injected directly into the femoral (n=4) or saphenous
Discussion
Since its discovery, the majority of studies involving TRPV1 have focused on its role in transducing thermal stimuli (Caterina et al 1997, Davis et al 2000). However, recent studies have shown that TRPV1 is expressed by a majority of bladder and colonic afferents, which theoretically would not be exposed to noxious temperatures capable of exciting TRPV1 (Robinson et al 2004, Brierley et al 2005, Hwang et al 2005, Christianson et al 2006). Also, data from our laboratories have demonstrated that
Acknowledgments
Supported by NIH grants NS050758 (B.M.D.); NS23725 (H.R.K.); NS051021 (J.A.C.).
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