Astrocytic Ca2+ responses in the spinal dorsal horn by noxious stimuli to the skin.

The role of astrocytes in the spinal dorsal horn (SDH) for sensory information processing under normal conditions is poorly understood. In this study, we investigated whether SDH astrocytes respond to noxious and innocuous stimuli to the skin of normal mice using in vivo two-photon Ca2+ imaging under anesthesia. We found that noxious stimulation evoked by intraplantar formalin injection provoked an elevation in intracellular Ca2+ levels in SDH astrocytes. By contrast, neither instantaneous noxious pinching nor innocuous stimuli (cooling or brushing) to the hindpaw elicited astrocytic Ca2+ responses. Thus, SDH astrocytes could respond preferentially to a strong and/or sustained noxious stimulus.