Roles of isolectin B4-binding afferents in colorectal mechanical nociception

Area of Science:

• Neuroscience
• Visceral Pain Research
• Sensory Neuron Biology

Background:

• Isolectin B4-binding (IB4+) dorsal root ganglion (DRG) neurons differ from peptidergic DRG neurons in spinal cord localization and nociception roles.
• The proportion of IB4+ neurons in colonic DRG (c-DRG) and their function in colorectal mechanonociception remain unclear.

Purpose of the Study:

• To quantify the IB4+ population in mouse c-DRG neurons.
• To investigate the role of IB4+ c-DRG neurons in colorectal mechanonociception.

Main Methods:

• Labeling c-DRG neurons with Fast Blue in C57BL/6J mice.
• Quantifying IB4+ binding in L6 DRG neurons.
• Selective ablation of IB4+ c-DRG neurons using IB4-conjugated saporin.
• Assessing nociceptive behaviors following colorectal distension.
• Characterizing colorectal afferent classes via single-fiber recordings.

Main Results:

• 61% of L6 c-DRG neurons were IB4+, with 95% of these being peptidergic.
• Ablation with IB4-saporin reduced IB4+ c-DRG neurons to 37%, primarily affecting those with strong to medium IB4+ intensity.
• No significant changes in nociceptive behaviors or afferent proportions were observed after ablation.

Conclusions:

• More than half of viscerosensory L6 c-DRG neurons in C57BL/6J mice are IB4+.
• Contrary to findings in cutaneous pathways, IB4+ c-DRG neurons with strong-to-medium intensity do not significantly contribute to colorectal mechanonociception.