A norepinephrine‐dependent glial calcium wave travels in the spinal cord upon acoustovestibular stimuli

Abstract

Although calcium waves have been widely observed in glial cells, their occurrence in vivo during behavior remains less understood. Here, we investigated the recruitment of glial cells in the hindbrain and spinal cord after acousto-vestibular (AV) stimuli triggering escape responses using in vivo population calcium imaging in larval zebrafish. We observed that gap-junction-coupled spinal glial network exhibits large and homogenous calcium increases that rose in the rostral spinal cord and propagated bi-directionally toward the spinal cord and toward the hindbrain. Spinal glial calcium waves were driven by the recruitment of neurons and in particular, of noradrenergic signaling acting through α-adrenergic receptors. Noradrenergic neurons of the medulla-oblongata (NE-MO) were revealed in the vicinity of where the calcium wave started. NE-MO were recruited upon AV stimulation and sent dense axonal projections in the rostro-lateral spinal cord, suggesting these cells could trigger the glial wave to propagate down the spinal cord. Altogether, our results revealed that a simple AV stimulation is sufficient to recruit noradrenergic neurons in the brainstem that trigger in the rostral spinal cord two massive glial calcium waves, one traveling caudally in the spinal cord and another rostrally into the hindbrain.

Radial astrocyte synchronization modulates the visual system during behavioral-state transitions

“…In mammals 21 , 32 and zebrafish, 27 , 33 NE induces Ca 2+ transients in astrocytes and RAs. Therefore, we tested whether the RAs in the OT sense the release of NE.…”

“… 29 In the rostral spinal cord, acousto-vestibular stimuli induce RA Ca 2+ waves traveling bi-directionally to the hindbrain and the caudal spinal cord. 33 In the hindbrain, RAs integrate errors in visual feedback during visuo-motor behaviors to trigger futility. In contrast to our results, the latter phenomenon is not mediated by the LC but rather triggered by the noradrenergic cluster of the medulla oblongata (NE-MO).…”

Trans-segmental imaging in the spinal cord of behaving mice

“…Notably, the significantly larger FOV allowed us to reveal that even focally delivered sensory stimuli could evoke remarkably widespread, trans-segmental calcium excitation in dorsal horn astrocytes, while isolated running bouts did not. Future studies will need to determine the full extent (in rostrocaudal and dorsoventral directions), underlying mechanisms (e.g., descending noradrenergic, local glutamatergic signaling, gap junction involvement), behavioral dependencies (e.g., motor activity), and modulatory effects of this widespread astrocyte activity on spinal neural circuits and behavior (e.g., trans-segmental sensitization) [14][15][16] . Innocuous pinch evoked only sparse activity in isolated ROI clusters (Fig.…”