RESUMO
Consciousness is lost within seconds upon cessation of cerebral blood flow. The brain cannot store oxygen, and interruption of oxidative phosphorylation is fatal within minutes. Yet only rudimentary knowledge exists regarding cortical partial oxygen tension (Po2) dynamics under physiological conditions. Here we introduce Green enhanced Nano-lantern (GeNL), a genetically encoded bioluminescent oxygen indicator for Po2 imaging. In awake behaving mice, we uncover the existence of spontaneous, spatially defined "hypoxic pockets" and demonstrate their linkage to the abrogation of local capillary flow. Exercise reduced the burden of hypoxic pockets by 52% compared with rest. The study provides insight into cortical oxygen dynamics in awake behaving animals and concurrently establishes a tool to delineate the importance of oxygen tension in physiological processes and neurological diseases.
Assuntos
Córtex Cerebral , Circulação Cerebrovascular , Hipóxia Encefálica , Medições Luminescentes , Saturação de Oxigênio , Oxigênio , Animais , Camundongos , Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/diagnóstico por imagem , Córtex Cerebral/metabolismo , Oxigênio/sangue , Oxigênio/metabolismo , Pressão Parcial , Hipóxia Encefálica/sangue , Hipóxia Encefálica/diagnóstico por imagem , Hipóxia Encefálica/metabolismo , Vasodilatação , Medições Luminescentes/métodos , Luciferases/genética , Luciferases/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Hipercapnia/sangue , Hipercapnia/diagnóstico por imagem , Hipercapnia/metabolismoRESUMO
Information transfer within neuronal circuits depends on the balance and recurrent activity of excitatory and inhibitory neurotransmission. Chloride (Cl-) is the major central nervous system (CNS) anion mediating inhibitory neurotransmission. Astrocytes are key homoeostatic glial cells populating the CNS, although the role of these cells in regulating excitatory-inhibitory balance remains unexplored. Here we show that astrocytes act as a dynamic Cl- reservoir regulating Cl- homoeostasis in the CNS. We found that intracellular chloride concentration ([Cl-]i) in astrocytes is high and stable during sleep. In awake mice astrocytic [Cl-]i is lower and exhibits large fluctuation in response to both sensory input and motor activity. Optogenetic manipulation of astrocytic [Cl-]i directly modulates neuronal activity during locomotion or whisker stimulation. Astrocytes thus serve as a dynamic source of extracellular Cl- available for GABAergic transmission in awake mice, which represents a mechanism for modulation of the inhibitory tone during sustained neuronal activity.