Shapes of astrocyte networks in the juvenile brain

Houades, Vanessa; Rouach, Nathalie; Ezan, Pascal; Kirchhoff, Frank; Koulakoff, Annette; Giaume, Christian

doi:10.1017/s1740925x06000081

Cited by 87 publications

(86 citation statements)

References 58 publications

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“…The number of biocytin staining cells in 14 syncytia varied from 26 to 131 with an average of 79 6 35 cells (6standard deviation [SD]). Both the average coupling and its associated SD are consistent with two previous reports on this brain region, i.e., D 'Ambrosio et al (1998) reported a coupling that varied from 20 to up to more than 100 cells, and Houades et al (2006) reported an average coupling of 83 6 32 (n 5 13).…”

Section: Distances Between Directly Coupled Astrocytes Insupporting

confidence: 90%

Electrical coupling of astrocytes in rat hippocampal slices under physiological and simulated ischemic conditions

Wang

Kimelberg

et al. 2009

Glia

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Mammalian protoplasmic astrocytes are extensively coupled through gap junction channels but the biophysical properties of these channels under physiological and ischemic conditions in situ are not well defined. Using confocal morphometric analysis of biocytin-filled astrocytic syncytia in rat hippocampal CA1 stratum radiatum we found that each astrocyte directly couples, on average, to 11 other astrocytes with a mean interastrocytic distance of 45 microm. Voltage-independent and bidirectional transjunctional currents were always measured between directly coupled astrocyte pairs in dual voltage-clamp recordings, but never from astrocyte-NG2 glia or astrocyte-interneuron pairs. The electrical coupling ratio varied considerably among astrocytes in developing postnatal day 14 rats (P14, 0.5-12.4%, mean = 3.6%), but became more constant in young adult P21 rats (0.18-3.9%, mean = 1.6%), and the coupling ratio declined exponentially with increasing pair distance. Electrical coupling was not affected by short-term oxygen-glucose deprivation (OGD) treatment, but showed delayed inhibition in an acidic extracellular pH of 6.4. Combination of acidic pH (6.4) and OGD, a condition that better represents cerebral ischemia in vivo, accelerated the inhibition of electrical coupling. Our results show that, under physiological conditions, 20.7-24.2% of K(+) induced currents can travel from any astrocytic soma in CA1 stratum radiatum to the gap junctions of the nearest neighbor astrocytes, but this should be severely inhibited as a consequence of the OGD and acidosis seen in the ischemic brain.

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Section: Distances Between Directly Coupled Astrocytes Insupporting

confidence: 90%

Electrical coupling of astrocytes in rat hippocampal slices under physiological and simulated ischemic conditions

Wang

Kimelberg

et al. 2009

Glia

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“…1D) and to the coupling confinement within OG. This phenomenon has already been observed in the hippocampus at the level of the pyramidal cell layer (26). Together, these properties indicate a certain degree of independence of each OG in terms of astroglial GJC that could restrain transfer of information between OGs and contribute to the accuracy of the glomerular map.…”

Section: Discussionsupporting

confidence: 58%

Plasticity of astroglial networks in olfactory glomeruli

Roux

Benchenane

Rothstein

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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119

118

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Several recent findings have shown that neurons as well as astrocytes are organized into networks. Indeed, astrocytes are interconnected through connexin-formed gap junction channels allowing exchanges of ions and signaling molecules. The aim of this study is to characterize astrocyte network properties in mouse olfactory glomeruli where neuronal connectivity is highly ordered. Dyecoupling experiments performed in olfactory bulb acute slices (P16-P22) highlight a preferential communication between astrocytes within glomeruli and not between astrocytes in adjacent glomeruli. Such organization relies on the oriented morphology of glomerular astrocytes to the glomerulus center and the enriched expression of two astroglial connexins (Cx43 and Cx30) within the glomeruli. Glomerular astrocytes detect neuronal activity showing membrane potential fluctuations correlated with glomerular local field potentials. Accordingly, gap junctional coupling of glomerular networks is reduced when neuronal activity is silenced by TTX treatment or after early sensory deprivation. Such modulation is lost in Cx30 but not in Cx43 KO mice, indicating that Cx30-formed channels are the molecular targets of this activity-dependent modulation. Extracellular potassium is a key player in this neuroglial interaction, because (i) the inhibition of dye coupling observed in the presence of TTX or after sensory deprivation is restored by increasing [K + ] e and (ii) treatment with a K ir channel blocker inhibits dye spread between glomerular astrocytes. Together, these results demonstrate that extracellular potassium generated by neuronal activity modulates Cx30-mediated gap junctional communication between glomerular astrocytes, indicating that strong neuroglial interactions take place at this first relay of olfactory information processing.O lfactory glomeruli (OG) represent functional units where olfactory signals are first processed (1, 2). The combination of the anatomical organization and the functional activity results in a highly ordered spatial map of glomerular activation associated with each odor (3, 4). However, this well-described organization refers only to neuronal circuits, and information concerning astroglial connectivity is lacking. In the brain, astrocytes express the highest rate of connexins (Cxs), the protein constituents of gap junction channels that provide the molecular basis for direct cellto-cell communication. Though astrocytes were initially thought to form a glial syncitium, there is now evidence for a more specialized network organization (5). As increasing evidence argues for dynamic interactions between neurons and astrocytes (6), a coordinated population of astrocytes working in concert with neurons could contribute to sensory integration occurring in OG. The goal of this study is to determine how Cx-mediated intercellular communication in astrocytes is organized and modulated in this brain structure characterized by functional units. Features of OG astrocytes studied so far include their morphology (7,8), membrane...

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“…It is shown that astrocytes exhibit regional specificity in gap-junction coupling. Heterogeneous morphologies are observed in the gap junction between astrocytes in different regions of brain, such as cortex, hippocampus, corpus callosum and olfactory bulb (Houades et al 2006). By comparing the astroglial gap junction in six CNS regions (spinal cord, cortex, hypothalamus, cerebellum, optic nerve, hippocampus), the gap junction density and sensitivity also display the regional heterogeneity (Lee et al 1994).…”

Section: Crosstalk Between the Astrocytesmentioning

confidence: 99%