Sodium-Calcium Exchanger Mediates Sensory-Evoked Glial Calcium Transients in the Developing Retinotectal System

Abstract

Various types of sensory stimuli have been shown to induce calcium elevations in glia. However, a mechanistic understanding of the signalling pathways mediating sensory-evoked activity in glia in intact animals is still emerging. Here we demonstrate that during early development of the Xenopus laevis visual system, radial astrocytes in the optic tectum are highly responsive to sensory stimulation. Calcium transients occur spontaneously in radial astrocytes at rest and are abolished by silencing neuronal activity with tetrodotoxin. Visual stimulation drives temporally correlated increases in the activity patterns of neighbouring radial astrocytes. Following blockade of all glutamate receptors, visually-evoked calcium activity in radial astrocytes is enhanced, rather than suppressed, while the additional blockade of either glutamate transporters or sodium-calcium exchangers (NCX) fully prevents visually-evoked responses. Additionally, we demonstrate that blockade of NCX alone is sufficient to prevent visually-evoked responses in radial astrocytes, highlighting a pivotal role for NCX in glia during development.