In vivo calcium imaging shows that satellite glial cells have increased activity in painful states

Abstract

Satellite glial cells (SGCs) are important for proper neuronal function of primary sensory neurons to whom they provide homeostatic support. Most research of SGC function has been performed with in vitro studies, but recent advances in calcium imaging and transgenic mouse models have enabled this first in vivo study of single cell SGC function in mouse models of inflammation and neuropathic pain. We found that in naive condition SGCs do not respond in a time-locked fashion to neuronal firing. In painful inflammatory and neuropathic states we detected time-locked signals in a subset of SGCs, but only with suprathreshold stimulation of the sciatic nerve. Surprisingly therefore, we conclude that most calcium signals in SGCs seem to develop at arbitrary intervals not directly linked to neuronal activity patterns. More in line with expectations, our experiments also revealed that the number of active SGCs was increased under conditions of inflammation or nerve injury. This could reflect the increased requirement for homeostatic support across dorsal root ganglion neuron populations, which are more active during such painful states.