RESUMO
Various types of sensory stimuli have been shown to induce Ca2+ elevations in glia. However, a mechanistic understanding of the signaling pathways mediating sensory-evoked activity in glia in intact animals is still emerging. During early development of the Xenopus laevis visual system, radial astrocytes in the optic tectum are highly responsive to sensory stimulation. Ca2+ 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 neighboring radial astrocytes. Following blockade of all glutamate receptors (gluRs), visually evoked Ca2+ activity in radial astrocytes persists, while neuronal activity is suppressed. The additional blockade of either glu transporters or sodium-calcium exchangers (NCX) abolishes visually evoked responses in glia. Finally, 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.
Assuntos
Cálcio/metabolismo , Neuroglia/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Colículos Superiores/metabolismo , Proteínas de Xenopus/metabolismo , Animais , Animais Geneticamente Modificados/metabolismo , Astrócitos/citologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Neuroglia/citologia , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Estimulação Luminosa , Receptores de Glutamato/química , Receptores de Glutamato/metabolismo , Trocador de Sódio e Cálcio/antagonistas & inibidores , Colículos Superiores/crescimento & desenvolvimento , Tioureia/análogos & derivados , Tioureia/farmacologia , Xenopus laevis/crescimento & desenvolvimento , Xenopus laevis/metabolismo , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/farmacologiaRESUMO
Astrocytes are known to play many important roles in brain function. However, research underscoring the extent to which astrocytes modulate neuronal activity is still underway. Here we review the latest evidence regarding the contribution of astrocytes to neuronal oscillations across the brain, with a specific focus on how astrocytes respond to changes in brain state (e.g., sleep, arousal, stress). We then discuss the general mechanisms by which astrocytes signal to neurons to modulate neuronal activity, ultimately driving changes in behavior, followed by a discussion of how astrocytes contribute to respiratory rhythms in the medulla. Finally, we contemplate the possibility that brain stem astrocytes could modulate brainwide oscillations by communicating the status of oxygenation to higher cortical areas.
