The ability to switch behavioral states is essential for animals to adapt and survive. Here, we demonstrate how norepinephrine (NE) activation of radial astrocytes alters visual processing in the optic tectum (OT) of developing Xenopus laevis. NE activates calcium transients in radial astrocytes through α1-adrenergic receptors. NE and radial astrocyte activation shift OT response selectivity to preferentially respond to looming stimuli, associated with predation threat. NE-mediated astrocytic release of ATP/adenosine reduces excitatory transmission by retinal ganglion cell axons, without affecting inhibitory transmission in the OT. Blockade of adenosine receptors prevents both decreased neurotransmission and the selectivity shift. Chemogenetic activation of tectal radial astrocytes mimics NE's effects and enhances behavioral detection of looming stimuli in freely swimming animals, whereas chelating calcium in astrocytes to block transients prevents the selectivity shift. NE signaling via radial astrocytes improves network signal-to-noise for detecting threatening stimuli, with important implications for sensory processing and behavior.
Benfey et al. (Wed,) studied this question.