Abstract
The transient receptor potential cation channel subfamily V member 1 (TRPV1) is known as a thermosensor and integrator of inflammation-induced hyperalgesia. TRPV1 is expressed in a subpopulation of primary afferent neurons that express several different neurotransmitters. The role of the TRPV1 channel in the development of hyperalgesia is established, but the role of the neurotransmitter glutamate, used partially by the same neuronal population and thus probably mediating the response, is still under investigation. We have used a Trpv1-Cre mouse line in which we either ablated Trpv1-Cre expressing neurons or induced vesicular glutamate transporter 2 (Vglut2) deficiency in Trpv1-Cre expressing neurons and investigated specific states of hyperalgesia after persistent inflammation. Furthermore, by pharmacologic inhibition of substance P (SP) or calcitonin gene-related peptide (CGRP) signaling in Vglut2-deficient mice, we also evaluated the contribution of SP or CGRP to inflammation-induced hyperalgesia, with or without the presence of vesicular glutamate transporter 2 (VGLUT2)-mediated glutamatergic transmission in Trpv1-Cre neurons. This examination, together with c-Fos analyses, showed that VGLUT2-mediated glutamatergic transmission in Trpv1-Cre afferents together with SP or CGRP is essential for the development of the heat hyperalgesia associated with persistent inflammation. Additionally, SP-, CGRP-, and VGLUT2-mediated transmission together were found to play a role in the development of mechanical hyperalgesia after persistent inflammation.
Footnotes
- Received September 10, 2013.
- Accepted November 25, 2013.
M.C.L. and K.K. contributed equally to this work.
This work was supported by grants from the Swedish Research Council (medicine); Uppsala University; and the foundations of K. and A. Wallenberg, Å. Wiberg, M. Bergwall, Åhlén, P. & A. Hedlund, T. Nilson, G. & J. Anér, L. Hierta, Jeanssons and the Royal Swedish Academy of Sciences. K.K. is a Royal Swedish Academy of Sciences Research Fellow supported by a grant from the Knut and Alice Wallenberg Foundation.
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- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics
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