Light-evoked expansion of subretinal space volume in the retina of the frog

Huang, Bo; Karwoski, Chester J.

doi:10.1523/jneurosci.12-11-04243.1992

Cited by 87 publications

(82 citation statements)

References 26 publications

(41 reference statements)

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“…Consistent with the [K+]-induced changes in RPE cell volume , Huang & Karwoski (1992) showed in a frog eyecup preparation that light caused a decrease in 'probe' ion concentration in the subretinal space, suggesting a volume increase of 5-9 %. They hypothesized that the subretinal space volume increase was caused by a decrease in the volume of the RPE, perhaps due to the exit of K+ and Cl-through the apical and basolateral membranes, respectively.…”

Section: Solute-induced Volume Changessupporting

confidence: 58%

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K+ and Cl‐ transport mechanisms in bovine pigment epithelium that could modulate subretinal space volume and composition.

Bialek

Miller

1994

The Journal of Physiology

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1. Conventional and ion-selective double-barrelled microelectrodes were used in an in vitro bovine retinal pigment epithelium (RPE)-choroid preparation to measure the changes in membrane voltage, resistance and intracellular K+ and Cl-activities produced by small, physiological changes in extracellular potassium ([K+]0).2. In the intact eye, light-induced changes in [K+]. occur in the extracellular (or subretinal) space that separates the neural retina and the RPE apical membrane. These [K+1 changes can be approximated in vitro by decreasing apical bath [K+]. from 5 to 2 mM.3. This in vitro change in [K+1 simultaneously decreased intracellular Cl-and K+ activities (a4 and ak) by 25 + 6 mM (n = 8) and 19 + 7 mM (n = 4) (mean + S.D.), respectively.In control Ringer solution (5 mm [K+]0) a', and a' were 65+10 mm (n = 28) and 65 + 8 mM (n = 6), respectively. The [K+]t-induced decreases in a', and a' were both significantly inhibited, either by blocking the apical membrane K+ conductance with Ba2+ or the basolateral membrane Cl-conductance with DIDS (4,4'-diisothiocyano-stilbene-2,2'-disulphonic acid). 5. Transepithelial current pulses were used to determine the relative basolateral membrane Cl-conductance, T5s, was -0-6 (n = 3), and the relative apical membrane K+ conductance, TK, was -0'7 (n = 2).Step changes in basal bath [Kt]o were used to estimate the relative basolateral membrane K+ conductance, TBAS, was -0 34 (n = 3). 6. These data show that the apical membrane K+ conductance and the basolateral membrane Cl-conductance are electrically coupled. In vivo, this coupling could have significant functional importance by modulating the relative hydration of the subretinal space, regulating RPE cell volume, and subretinal space.In the posterior portion of the vertebrate eye the apical membrane of the retinal pigment epithelium (RPE) and the photoreceptors communicate across a small extracellular or subretinal space. The basolateral membrane faces a different extracellular environment which is produced by the choroidal blood supply. The flow of metabolites, ions and fluid between these extracellular spaces is mediated by a variety of apical and basolateral membrane transport

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Section: Solute-induced Volume Changessupporting

confidence: 58%

“…Light-induced changes in retinal volume have been observed in several preparations from frog, chick and cat (Huang & Karwoski, 1992;Li et al 1992;R. Steinberg, personal communication).…”

Section: Solute-induced Volume Changesmentioning

confidence: 99%

K+ and Cl‐ transport mechanisms in bovine pigment epithelium that could modulate subretinal space volume and composition.

Bialek

Miller

1994

The Journal of Physiology

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“…Ion-selective microelectrodes (ISM Es) were prepared with a liquid potassium ion exchanger (I E 190, W PI) and calibrated in conventional fashion. In addition to its selectivity for potassium ions, the ion exchanger is highly selective for quaternary ammonium ions (Hansen and Olsen, 1980;Huang and Karwoski, 1992). Changes in extracellular space (EC S) volume can be detected by adding 10 mM TM A-C l to extracellular fluid (Ransom et al, 1985;Huang and Karwoski, 1992).…”

Section: Animalsmentioning

confidence: 99%

A Novel Role of Vasopressin in the Brain: Modulation of Activity-Dependent Water Flux in the Neocortex

et al. 2001

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The brain contains an intrinsic vasopressin fiber system the function of which is unknown. It has been demonstrated recently that astrocytes express high levels of a water channel, aquaporin-4 (AQP4). Because vasopressin is known to regulate aquaporin expression and translocation in kidney collecting ducts and thereby control water reabsorption, we hypothesized that vasopressin might serve a similar function in the brain. By recording intrinsic optical signals in an acute cortical slice preparation we showed that evoked neuronal activity generates a radial water flux in the neocortex. The rapid onset and high capacity of this flux suggest that it is mediated through the AQP4-containing astrocytic syncytium that spans the entire thickness of the neocortical mantle. Vasopressin and vasopressin receptor V1a agonists were found to facilitate this flux. V1a antagonists blocked the facilitatory effect of vasopressin and reduced the water flux even in the absence of any exogenous agonist. V2 agonists or antagonists had no effect. These data suggest that vasopressin and V1a receptors play a crucial role in the regulation of brain water and ion homeostasis, most probably by modulating aquaporin-mediated water flux through astrocyte plasma membranes.

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“…ISMEs were prepared with a liquid potassium ion exchanger (Corning 477317) and calibrated in conventional fashion. In addition to its selectivity for potassium ions, the ion exchanger is highly selective for quaternary ammonium ions (Hansen and Olsen 1980, Huang and Karwoski 1992a, Huang and Karwoski 1992b. For detection of changes in extracellular space volume, 10mM tetramethylammoniumchloride (TMACl) were added to the extracellular fluid (Ransom et al 1985, Huang andKarwoski 1992b).…”

Section: Ion-selective Microelectrodesmentioning

confidence: 99%

“…Changes in extracellular TMA-concentration can be interpreted as alterations in ECS volume. Relative alterations of ECS volume were calculated using the following expression (Dietzel et al 1980 In the presence of quaternary ammonium ions, the used ISMEs are virtually blind to potassium ions (Huang and Karwoski 1992b). Fig.…”

Section: Ion-selective Microelectrodesmentioning

confidence: 99%

Cell swelling and ion redistribution assessed with intrinsic optical signals

Witte

Niermann

Holthoff

2001

An. Acad. Bras. Ciênc.

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Cell volume changes are associated with alterations of intrinsic optical signals (IOS). In submerged brain slices in vitro, afferent stimulation induces an increase in light transmission. As assessed by measurement of the largely membrane impermeant ion tetramethylammonium (TMA) in the extracellular space, these IOS correlate with the extent and time course of the change of the extracellular space size. They have a high signal to noise ratio and allow measurements of IOS changes in the order of a few percent. Under conditions of reduced net KCl uptake (low Cl solution) a directed spatial buffer mechanism (K syphoning) can be demonstrated in the neocortex with widening of the extracellular space in superficial layers associated with a reduced light transmission and an increase of extracellular K concentration. The nature of the IOS under pathophysiological conditions is less clear. Spreading depressions first cause an increase of light transmission, then a decrease. Such a decrease has also been observed following application of NMDA where it was associated with structural damage. Pharmacological analyses suggest that under physiological conditions changes of extracellular space size are mainly caused by astrocytic volume changes while with strong stimuli and under pathophysiological conditions also neuronal swelling occurs. With reflected light usually signals opposite to those observed with transmitted light are seen. Recording of IOS from interface slices gives very complex signals since under these conditions an increase of light transmission has been reported to be superimposed by a decrease of the signal due to mechanical lensing effects of the slice surface. Depending on the method of measurement and the exact conditions, several mechanisms may contribute to IOS. Under well defined conditions IOS are a useful supplementary tool to monitor changes of extracellular volume both in space and time.

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Light-evoked expansion of subretinal space volume in the retina of the frog

Cited by 87 publications

References 26 publications

K+ and Cl‐ transport mechanisms in bovine pigment epithelium that could modulate subretinal space volume and composition.

K+ and Cl‐ transport mechanisms in bovine pigment epithelium that could modulate subretinal space volume and composition.

A Novel Role of Vasopressin in the Brain: Modulation of Activity-Dependent Water Flux in the Neocortex

Cell swelling and ion redistribution assessed with intrinsic optical signals

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