CNS myeloid cells critically regulate heat hyperalgesia

Authors
S Kalin, KR Miller, RE. Kalin, M Jendrach, C Witzel, FL Heppner

Lab
Department of Neuropathology, Charite_platz, Berlin, Germany

Journal
The Journal of Clinical Investigation

Abstract
Activation of non-neuronal microglia is thought to play a causal role in spinal processing of neuropathic pain. To specifically investigate microglia-mediated effects in a model of neuropathic pain and overcome the methodological limitationsof previous approaches exploring microglia function upon nerve injury, we selectively ablated resident microglia by intracerebroventricular ganciclovir infusion into male CD11b-HSVTK–transgenic mice, which was followed by a rapid, complete, and persistent (23 weeks) repopulation of the CNS by peripheral myeloid cells. In repopulated mice that underwent sciatic nerve injury, we observed a normal response to mechanical stimuli, but an absence of thermal hypersensitivity ipsilateralto the injured nerve. Furthermore, we found that neuronal expression of calcitonin gene–related peptide (CGRP), which isa marker of neurons essential for heat responses, was diminished in the dorsal horn of the spinal cord in repopulated mice. These findings identify distinct mechanisms for heat and mechanical hypersensitivity and highlight a crucial contribution of CNS myeloid cells in the facilitation of noxious heat.

BIOSEB Instruments Used:
Von Frey Filaments (Bio-VF-M)