Expression of vesicular glutamate transporters in transient receptor potential ankyrin 1 (TRPA1)-positive neurons in the rat trigeminal ganglion

• Published in: Brain research Vol. 1690; pp. 31 - 39
• Main Authors: Kim, Yun Sook, Kim, Sung Kuk, Lee, Jae Sik, Ko, Sang Jin, Bae, Yong Chul
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-07-2018
• Subjects: Animals; Cold pain; Immunohistochemistry; Inflammation - metabolism; Inflammation - pathology; Male; Neurons - cytology; Neurons - metabolism; Neurons - pathology; Rats, Sprague-Dawley; Trigeminal; Trigeminal Ganglion - cytology; Trigeminal Ganglion - metabolism; Trigeminal Ganglion - pathology; TRPA1; TRPA1 Cation Channel - metabolism; Up-Regulation; Vesicular Glutamate Transport Protein 1 - metabolism; Vesicular Glutamate Transport Protein 2 - metabolism; Vesicular glutamate transporter; Vibrissae; Immunohistochemistry; LM; PV; Vesicular glutamate transporter; GFP; NF200; FITC; VGLUT3; ANOVA; VGLUT2; Cy; VGLUT1; NDS; PBS; SDS; TBS; TRPA1; TRPV1; Trigeminal; PB; TG; DRG; IB4; Cold pain; CGRP; CFA
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2018.04.010

•The majority of TRPA1+ neurons in the trigeminal ganglion (TG) express VGLUT2.•A small fraction of TRPA1+ neurons in the TG coexpress VGLUT1.•Expression of VGLUT2 and TRPA1 in the TG is increased following inflammation.
Transient receptor potential ankyrin 1 (TRPA1), a cold receptor in sensory neurons activated by a variety of stimuli, is implicated in nociception and mechanotransduction. To help understand the vesicular glutamate transporter (VGLUT)-mediated glutamate signaling in TRPA1-immunopositive (+) neurons, we examined the expression of VGLUT1 and VGLUT2 in the TRPA1+ neurons in the male rat trigeminal ganglion (n = 19) under normal conditions and following experimental inflammation in the vibrissal pad by light microscopic immunohistochemistry (n = 11), western blot (n = 8), and quantitative analysis.
One half (50.8%, 250/492) of the TRPA1+ neurons expressed VGLUT2, and a small fraction (8.3%, 57/683) also expressed VGLUT1. The majority of the VGLUT2-expressing TRPA1+ (VGLUT2+/TRPA1+) neurons coexpressed the markers of peptidergic and non-peptidergic neurons, CGRP, IB4, and TRPV1 but not the markers of neurons with myelinated fibers, NF200 and parvalbumin. In contrast, most VGLUT1+/TRPA1+ neurons coexpressed NF200 and parvalbumin but rarely expressed CGRP, IB4, or TRPV1. Following experimental inflammation, the fraction of VGLUT2+ (experimental vs. control: 34.7% vs. 22.3%), TRPA1+ (39.3% vs. 25.3%), and VGLUT2+/TRPA1+ (60.7% vs. 49.7%) neurons and the protein levels for TRPA1 and VGLUT2 increased significantly, compared to control, whereas the fraction of VGLUT1+ and VGLUT1+/TRPA1+ neurons and the protein level for VGLUT1 remained unchanged.
These findings suggest that both VGLUT1 and VGLUT2 are involved in the glutamate signaling in TRPA1+ neurons under normal conditions in the male rats, and raise a possibility that VGLUT2 may play a role in the TRPA1-induced hypersensitivity following inflammation.