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. 2018 Sep 4;9:1000. doi: 10.3389/fphar.2018.01000

Table 1.

Characteristics of DRG neurons.

Small neurons (diameter ≤ 30 μm)
 Large neurons (diameter > 30 μm)
Unmyelinated C fibers or thinly myelinated Aδ-fibers Thickly-myelinated Aα/Aβ fibers
Isolectin-IB4 labeling YES (non-peptidergic) NO (peptidergic) NO
Distribution 33% 33% 33%
Transcription factors (during neurons development) Neurogenin 1 (determines neuron formation) Neurogenin 2 (regulates neuron formation)
RUNX1 (maintained by NGF signaling, inhibits neuropeptide expression) Reduction of RUNX1 and Mrgpr (due to NGF signaling decrease) RUNX3 (inhibits TrkB expression and contributes to specification of TrkC-positive neurons)
Growth factor receptors (adult neurons) GDNF and c-Ret co-receptors
GDNF family receptor α-2 GDNF family receptor α-3
P2X3 (absence of TrkA receptors) TrkA receptors TrkB receptors TrkC receptors
Main
Neuropeptides
  • simple –

    Substance P, NKA

  • simple –

    CGRP, Somatostatin

  • simple –

    VIP, PACAP-27 and 28 (upregulated after nerve injury)

  • simple –

    Galanin

  • simple –

    Cholescystokinin (upregulated after nerve injury)
  • simple –

    Substance P (upregulated after nerve injury)

  • simple –

    CGRP

  • simple –

    Neuropeptide Y (upregulated after nerve injury)
Neuronal cytoskeleton Peripherin NF200
Cell adhesion molecules Necl-1 Necl-1 Necl-1

The table illustrates the characteristics of DRG neurons regarding isolectin IB4-labeling, growth factor receptors, transcription factors, main neuropeptides, neuronal cytoskeleton composition, and cell adhesion molecules. GDNF, glial cell line-derivated neurotrophic factor; Trk, Tropomyosin receptor-kinase; P2X3, P2X purinergic receptor subunit 3; RUNX, Runt-related transcription factor; NGF, Nerve Growth Factor; Mrgpr, Mas-related G- protein coupled receptor; NKA, neurokinin A; CGRP, Calcitonin Gene-Related Peptide; VIP, Vasoactive Intestine Peptide; PACAP, Pituitary Adenylate Cyclase-Activating Polypeptide; NF, Neurofilament; Necl, Nectin-like molecule. The increased gradient of Necl-1expression between small non-peptidergic, small peptidergic and large neurons are represented by an increasing size of letters.