This effect was prevented by coadministration of the TRPV1-selective antagonist N-(4-tertiarybutylphenyl)-4-(3-chloropyridin-2-yl) tetrahydropyrazine-1(2H)-carbox-amide (BCTC, Figure 1A). Capsaicin had no effect on mechanical thresholds in TRPV1−/− mice (Figure 1B). Intrathecal capsaicin could act on either postsynaptic TRPV1 expressed in spinal cord neurons or on presynaptic TRPV1 expressed at the primary afferent terminals of sensory neurons. To distinguish between these possibilities, we generated mice in which TRPV1-expressing peripheral neurons are ablated by intraperitoneal injection of the ultrapotent TRPV1 agonist resiniferatoxin

Galunisertib concentration (RTX). RTX treatment eliminated TRPV1 mRNA in dorsal root ganglia without altering mRNA levels in the spinal cord (Figure 1C). RTX treatment appeared to be effective in completely ablating peripheral neurons expressing TRPV1, including their central terminals, because there was complete loss of TRPV1 immunoreactivity in DRG neurons (Figures S1A and S1B available online), nearly complete (98%) loss of capsaicin-induced calcium increases in DRG cell bodies (Figure S1D), and complete loss of capsaicin response of presynaptic terminals (Figure S1C). However, in contrast

to TRPV1−/− mice, intrathecal capsaicin injection was still able to effectively induce mechanical hypersensitivity in RTX-treated mice (Figure 1B), suggesting a site of action on central neurons. High-resolution

electron microscopic selleck compound analysis of the lumbar spinal cord below revealed TRPV1 was localized not only to presynaptic terminals, as expected (Figure 1D), but also to postsynaptic dendrites in the dorsal horn (Figure 1E), and postsynaptic cell soma (Figure 1F). No TRPV1 immunoreactivity was observed in the dorsal horn of TRPV1−/− mice (Figure 1G). We next sought to identify the population of postsynaptic spinal cord neurons that functionally express TRPV1. SG neurons of the spinal dorsal horn are a heterogenous population of interneurons (Maxwell et al., 2007 and Todd and McKenzie, 1989) that receive direct inputs from primary afferent fibers (Yasaka et al., 2007). TRPV1 immunoreactivity was colocalized in postsynaptic dendrites with the GABA synthesizing enzyme glutamic acid decarboxylase 65 (GAD65) (Figure 2A). TRPV1 mRNA was detected in 76.7% of GAD65-enhanced green fluorescent protein (EGFP) positive SG neurons by single-cell RT-PCR (Figure 2B, upper). In contrast, the occurrence of TRPV1 mRNA in GAD65-EGFP negative SG neurons was lower (25%, Figure 2B, lower). To test for functional expression of TRPV1, we applied capsaicin (CAP) to spinal cord slices while recording from SG neurons.