Astrocytes have become increasingly recognized as critical elements for regulating neuronal development and function in the central nervous system. Recently, we have identified a population of astrocytes (genetically defined by the transcription factor Hes5) in the spinal dorsal horn (SDH) and shown that these astrocytes respond to intraplantar injection of capsaicin (a noxious stimulus) via α_1A-adrenoceptors (α_1A-ARs) activated by locus coeruleus descending noradrenergic (LC-NAergic) signals (Nat. Neurosci., 2020). In this study, to determine whether the activation of SDH astrocytes through α_1A-AR-mediated descending LC-NAergic signals is commonly observed by other noxious stimuli, we examined astrocytic Ca²⁺ responses in the SDH after intraplantar injection of formalin using two-photon microscopy. We found that intraplantar formalin induced Ca²⁺ responses in SDH astrocytes and that the astrocytic Ca²⁺ responses were suppressed by intrathecal pretreatment with an α_1A-AR antagonist. Furthermore, mice lacking α_1A-ARs in Hes5⁺ astrocytes failed to induce astrocytic Ca²⁺ responses in the SDH. Therefore, our findings suggest that activation of SDH astrocytes by noxious stimuli is commonly mediated by activation of α_1A-AR through descending LC-NAergic signals.