Noradrenaline Drives Structural Changes in Astrocytes and Brain Extracellular Space

Abstract Locus coeruleus neurons innervate multiple brain regions. These neurons release noradrenaline through their axonal varicosities into the extracellular space through synaptic and volume transmission during states of arousal. The extracellular space is a channel that surrounds brain cells, facilitating diffusion-mediated transport of signaling molecules, ions, and drugs. Distal astrocytic processes expressing β-adrenergic receptors are targets of noradrenaline. In this review, we discuss work in cortical tissue indicating that β-adrenergic agonist, isoproterenol, expands astrocytic processes. Isoproterenol-driven increase in volume of astrocytic processes contributes partially to decrease in the extracellular space volume from 22% to 18%. Decrease in the extracellular space volume suggests increased concentration of ions, neurotransmitters, and neuromodulators diffusing in the extracellular space, which, in turn, facilitates neuronal signaling during noradrenaline release in cortex.