VGLUTs in Peripheral Neurons and the Spinal Cord: Time for a Review
Figure 1
Broad VGLUT expression in mouse visceral and nonvisceral DRG neurons. Bright-field ((a)–(c)) and immunofluorescence ((d)–(l)) photomicrographs of DRG sections incubated with VGLUT1, VGLUT2, or VGLUT3 antisense riboprobes ((a), (b), (c), resp.) or VGLUT1 ((d), (g), (j)), VGLUT2 ((e), (h), (i), (k)), or EGFP ((f), (l)) antibodies (EGFP, used as a reporter of VGLUT3 expressing neurons). Colocalizations with CGRP ((d)–(f), (j)–(l)) or IB4 ((g), (h)) are also shown. Colorectum ((j), (l)) or urinary bladder (k) DRG neurons are exposed by presence of the retrograde tracer FB ((j), (k), (l)). ((a)–(c)) VGLUT transcripts are detected in nonvisceral DRGs, VGLUT1 mostly in large and medium-sized NPs (black double arrowheads in (a)), VGLUT2 in many NPs spanning different cell body sizes (black double arrowheads in (b)), and VGLUT3 in a discrete number of usually small and some medium-sized NPs (black double arrowheads in (c)). Many NPs lacking VGLUTs are also detected (white double arrowheads in (a)–(c)). ((d)–(f)) The distribution of VGLUT1- (arrowheads in (d)) VGLUT2- (arrowheads and black double arrowheads in (e)), and EGFP-IR (arrowheads in (f)) nonvisceral DRG NPs correlates with the transcript counterparts shown in (a)–(c). While most CGRP-expressing nonvisceral DRG NPs coexpress with VGLUT2 (black double arrowheads in (e)), VGLUT1-, VGLUT3- (arrowheads in (d), (f)), and CGRP-IR (arrows in (d), (f)) NPs virtually always appear as independent subpopulations. Many VGLUT2-IR DRG NPs lacking CGRP are also detected (arrowheads in (e)). ((g), (h)) IB4 is virtually always present in VGLUT2-IR nonvisceral DRG NPs (black double arrowheads in (h)), while many other VGLUT2-only NPs are also observed (arrowheads in (h)). In contrast, VGLUT1- (arrowheads in (g)) and IB4-expressing (arrows in (g)) DRG NPs always belong to different subpopulations. (i) VGLUT2-membrane staining is detected in a number of nonvisceral DRG NPs (small arrowheads). ((j)–(l)) VGLUT1- (arrowheads and with double arrowhead in (j)), VGLUT2- (arrowheads and black double arrowheads in (k)), and EGFP-IR (arrowheads and white double arrowheads in (l)) are detected in visceral DRG NPs, with a similar cell soma distribution as observed for nonvisceral DRGs. CGRP-IR visceral DRG NPs are virtually always VGLUT2-IR (black double arrowheads in (k)), while NPs expressing the peptide (arrows in (j), (l)) and VGLUT1 (arrowheads and double arrowheads in (j)) or EGFP-IR NPs (arrowheads and double arrowheads in (l)) belong to different subpopulations. Scale bars: 50 μm ((c) = (a), (b); (h) = (d)–(g); (k) = (j); (l)); 20 μm (i). Data in figures (f) and (l) is previously unpublished, and the tissue has been processed according to the immunohistochemical procedures described in [54, 60–62].
