Quantitative Analysis of Mouse Dural Afferent Neurons Expressing TRPM8, VGLUT3, and NF200

Abstract

Objective.-To quantify the abundance of dural afferent neurons expressing transient receptor potential channel melastatin 8 (TRPM8), vesicular glutamate transporter 3 (VGLUT3), and neurofilament 200 (NF200) in adult mice.Background.-With the increasing use of mice as a model system to study headache mechanisms, it is important to understand the composition of dural afferent neurons in mice. In a previous study, we have measured the abundance of mouse dural afferent neurons that express neuropeptide calcitonin gene-related peptide as well as two TRP channels TRPV1 and TRPA1, respectively. Here, we conducted quantitative analysis of three other dural afferent subpopulations in adult mice.Methods.-We used the fluorescent tracer Fluoro-Gold to retrogradely label dural afferent neurons in adult mice expressing enhanced green fluorescent protein in discrete subpopulations of trigeminal ganglion (TG) neurons. Mechanoreceptors with myelinated fibers were identified by NF200 immunoreactivity. We also conducted Ca 21 -imaging experiments to test the overlap between TRPM8 and VGLUT3 expression in mouse primary afferent neurons (PANs).Results.-The abundance of TRPM8-expressing neurons in dural afferent neurons was significantly lower than that in total TG neurons. The percentages of dural afferent neurons expressing VGLUT3 and NF200 were comparable to those of total TG neurons, respectively. TRPM8 agonist menthol evoked Ca 21 influx in less than 7% VGLUT3-expressing PANs in adult mice.Conclusions.-TG neurons expressing TRPM8, VGLUT3, and NF200 all innervate adult mouse dura. TRPM8 and VGLUT3 are expressed in distinct subpopulations of PANs in adult mice. These results provide an anatomical basis to investigate headache mechanisms in mouse models. BACKGROUND AND OBJECTIVE Recent years have seen a rapid increase in the use of mouse as a model system to study the pathophysiology of headache. It is well established that the activation and sensitization of the primary afferent neurons (PANs) innervating the dura and cerebral blood vessels play a crucial role in the onset and maintenance of a headache episode.

Tetrodotoxin-sensitive sodium channels mediate action potential firing and excitability in menthol-sensitive Vglut3-lineage sensory neurons

“…In contrast to this model, Vglut3 -/mice are reported to have normal responses to cold stimuli, indicating that Vglut3 protein is not required for TRPM8-dependent behaviors in mice (Draxler et al, 2014). Furthermore, in sensory neurons innervating the dura and cerebral blood vessels, TRPM8 and Vglut3 protein expression do not overlap in adult mice (Ren et al, 2018). Thus, we speculate that menthol-sensitive neurons express the Slc17A8 locus during development rather than in mature DRG.…”

Tetrodotoxin-Sensitive Sodium Channels Mediate Action Potential Firing and Excitability in Menthol-Sensitive Vglut3-Lineage Sensory Neurons

“…In contrast to this model, Vglut3 Ϫ /Ϫ mice are reported to have normal responses to cold stimuli, indicating that Vglut3 protein is not required for TRPM8-dependent behaviors in mice (Draxler et al, 2014). Furthermore, in sensory neurons innervating the dura and cerebral blood vessels, TRPM8 and Vglut3 protein expression do not overlap in adult mice (Ren et al, 2018). Thus, we speculate that menthol-sensitive neurons express the Slc17a8 locus during development rather than in mature DRG.…”

TRP Channels as Potential Targets for Sex-Related Differences in Migraine Pain

“…Notably, TRPV1 is highly co-expressed with αCGRP (Ichikawa and Sugimoto, 2001 ; Bae et al, 2004 ), as well as with Substance P (SP) and P2X3 purinergic receptors. TRPV1 colocalizes with TRPA1 as well (Story et al, 2003 ; Bautista et al, 2005 ), whereas TRPM8 is expressed in a different subpopulation of nociceptors (Peier et al, 2002 ; Story et al, 2003 ; Okazawa et al, 2004 ; Ren et al, 2018 ).…”