Extracellular space volume changes in the rat spinal cord produced by nerve stimulation and peripheral injury

Svoboda, J.; Syková, Eva

doi:10.1016/0006-8993(91)91235-s

Cited by 94 publications

(67 citation statements)

References 37 publications

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“…Recently, the values of a and X. under normoxic conditions in vivo were determined in the spinal dorsal horn of the rat (Svoboda and Sykova, 1991). In the present study, the nonspecific TMA + uptake (k') (Nicholson and Phillips, 1981;Nicholson, 1992), which represents the linear concentration dependent loss of TMA + from the ECS to the in tracellular space, blood, or CSF, was also deter mined.…”

Section: Diffusion Parameters During Normoxiamentioning

confidence: 82%

“…In the present study, the nonspecific TMA + uptake (k') (Nicholson and Phillips, 1981;Nicholson, 1992), which represents the linear concentration dependent loss of TMA + from the ECS to the in tracellular space, blood, or CSF, was also deter mined. In our original study with the TMA + method, we were not able to incorporate k' into our curve-fitting procedure, and we found that many of the diffusion curves could not be fitted (Svoboda and Sykova, 1991), particularly their falling phase. In the present study, we incorporated linear uptake (k') and were able to fit almost all curves.…”

Section: Diffusion Parameters During Normoxiamentioning

confidence: 97%

“…The value of k' was found to be only two to three times (1.0-1.3 x 10-2 s -1) higher in rat striatal slices (Rice and Nichol son, 1991) or in hippocampal slices (McBain et al, 1990) than in cortex or spinal cord in vivo, which may reflect some loss of TMA + into the superfu sion medium in preparations in vitro. Each of the parameters ex, �, and k' within the dorsal hom gray matter remained the same in various layers (see also Svoboda and Sykova, 1991). The ex values were, however, significantly different in various cortical layers (Lehmenkiihler et al, 1993); e.g., in layers II and III, the mean ex values were 0.19 and 0.20, re spectively, while in layers V and VI, the mean ex values were 0.22 and 0.23.…”

Section: Diffusion Parameters During Normoxiamentioning

confidence: 99%

“…Recent experiments in vitro as well as in vivo demonstrated that the changes in intra-and extra cellular volume result in altered diffusion parame ters in ECS, which in turn would affect the activity related accumulation of ions, neuroactive sub stances, and metabolites in ECS and their movement toward the target cells and access to cap illaries (Nicholson and Rice, 1988;McBain et aI., 1990;Svoboda and Sykova, 1991;Lehmenkiihler et aI., 1993). In these studies the real-time iontopho retic method, which employs ion-selective micro electrodes (ISMs) to follow the diffusion of extra cellular markers applied by iontophoresis, was uti lized (Nicholson and Phillips, 1981;Nicholson, 1992).…”

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Extracellular Volume Fraction and Diffusion Characteristics during Progressive Ischemia and Terminal Anoxia in the Spinal Cord of the Rat

Syková

Svoboda

Polák

et al. 1994

J Cereb Blood Flow Metab

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Summary: Extracellular space (ECS) volume fraction(IX), ECS tortuosity (A), and nonspecific uptake (k'), three parameters affecting the diffusion of substances in ner vous tissue, were studied during ischemia and anoxia in the rat spinal cord gray matter in vivo. Progressive isch emia evoked by exsanguination, as well as anoxia evoked by respiratory or cardiac arrest, produced prominent ex tracellular K + and pH changes closely related to a de crease in blood pressure and amplitude of field potentials. With use of ion-selective microelectrodes, the changes in the diffusion parameters were measured by quantitative analysis of concentration-time profiles of tetramethylam monium (TMA +) applied by iontophoresis concomitantly with ionic shifts. Under normoxic conditions (in rats with blood pressure of 80-110 mm Hg) diffusion parameters in the dorsal hom gray matter at depth 500-900 fLm were as follows: IX = 0.20 ± 0.019, A = 1.62 ± 0.12, k' = 4.6 ± 2.5 x 10-3 s -1 (mean ± SD, n = 39). Extracellular K +, pH, and diffusion properties gradually changed during progressive ischemia. As the blood pressure fell to 50-60 mm Hg and field potential amplitude to 20-60%, K + rose to 6-12 mM, pHe fell by -0.05-0.1 pH unit, and volume fraction of the ECS significantly decreased, to IX = 0.16 ± 0.019 (n = 22). Even though the tortuosity remained vir tually constant, the nonspecific uptake significantly de creased to k' = 3.4 ± 1.8 x 10-3 S-I. As the blood pressure fell to 20-30 mm Hg and field potential ampli tude to 0-6%, K + rose to 60-70 mM, pHe fell by -0.6-0.8 pH unit, and all three diffusion parameters significantly 301changed. The ECS volume fraction decreased to a = 0.05 ± 0.021, tortuosity increased to A = 2.00 ± 0.24, and TMA + uptake decreased to k' = 1.5 ± 1.6 x 10 -3 S -1 (n = 12). No further increase in extracellular K + or changes in the IX were found during and up to 120 min after the death of the animal. However, there was a further signif icant increase in A = 2.20 ± 0.14 and decrease in k' = 0.4 ± 0.3 x 10-3 s -1 (n = 24). The acid shift reached its maximum level at -5-10 min after respiratory arrest and then the pHe gradually increased by -0.2 unit. Full re covery to "normoxic" diffusion parameters was achieved after reinjection of the blood or after an injection of nor adrenaline during severe ischemia, if this resulted in a rise in blood pressure above 80 mm Hg and a decrease in extracellular K + below 12 mM. At -10 and 30 min after this recovery, the ECS volume fraction significantly in creased above "normoxic" values, to IX = 0.25 ± 0.016 (n = 7) and IX = 0.30 ± 0.021 (n = 6), respectively. The A and k' were not significantly different from the values found under normoxic conditions. Our data represent the first detailed in vivo measurements of diffusion parame ters IX, A, and k' during and after progressive ischemia and anoxia. The observed substantial changes in the diffusion parameters could affect the diffusion and aggravate the accumulation of ions, neurotransmitters, metabolic sub stances, and drugs ...

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Section: Diffusion Parameters During Normoxiamentioning

confidence: 82%

Section: Diffusion Parameters During Normoxiamentioning

confidence: 97%

Section: Diffusion Parameters During Normoxiamentioning

confidence: 99%

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confidence: 99%

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Extracellular Volume Fraction and Diffusion Characteristics during Progressive Ischemia and Terminal Anoxia in the Spinal Cord of the Rat

Syková

Svoboda

Polák

et al. 1994

J Cereb Blood Flow Metab

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166

121

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“…5,6 This mechanism is hypothesized to be related to swelling of neurons and/or glial cells that has been shown to arise at sites of neuronal activity. [7][8][9] In addition, the increased blood flow to the active tissues has been shown to be accompanied by increased intravascular pressure, and increased production of extracellular fluid at sites of neuronal activity. 10,11 The net effect is a local increase in water content near active neural tissues which causes a higher MR signal intensity.…”

Section: Introductionmentioning

confidence: 99%

Detection of the neuronal activity occurring caudal to the site of spinal cord injury that is elicited during lower limb movement tasks

Kornelsen

Stroman

2007

Spinal Cord

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Study design: Functional magnetic resonance imaging (fMRI) of the spinal cord (spinal fMRI) was used to detect neuronal activity elicited by passive and active lower limb movement tasks, in regions caudal to the injury site in volunteers with spinal cord injury. Objectives: The objectives of this project are: (1) to assess the use of spinal fMRI as a tool for detecting neuronal function in the spinal cord below an injury, and (2) to characterize the neuronal response to active and passive movement tasks. Setting: Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Manitoba, Canada. Methods: fMRI of the spinal cord was carried out in 12 volunteers with cervical or thoracic spinal cord injuries. Spinal fMRI was carried out in a 1.5 T clinical MR system using established methods. Active and passive lower limb movement tasks were performed, and sagittal images spanning the entire lumbar spinal cord were obtained. Results: Activity was detected in all volunteers regardless of the extent of injury. During both active and passive participation, activity was seen caudal to the injury site, although the number of active voxels detected with passive movement was less than with the active movement task. Average percent signal change was 13.6% during active participation and 15.0% during passive participation. Conclusions: Spinal fMRI is able to detect a neuronal response during both active and passive lower limb movement tasks in the spinal cord caudal to the injury site.

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Glial depolarization evokes a larger potassium accumulation around oligodendrocytes than around astrocytes in gray matter of rat spinal cord slices

et al. 1999

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The cell membrane of astrocytes and oligodendrocytes is almost exclusively permeable for K+. Depolarizing and hyperpolarizing voltage steps produce in oligodendrocytes, but not in astrocytes, decaying passive currents followed by large tail currents (Itail) after the offset of a voltage jump. The aim of the present study was to characterize the properties of Itail in astrocytes, oligodendrocytes, and their respective precursors in the gray matter of spinal cord slices. Studies were carried out on 5- to 11-day-old rats, using the whole-cell patch clamp technique. The reversal potential (Vrev) of Itail evoked by membrane depolarization was significantly more positive in oligodendrocytes (-31.7+/-2.58 mV, n = 53) than in astrocytes (-57.9+/-2.43 mV, n = 21), oligodendrocyte precursors (-41.2+/-3.44 mV, n = 36), or astrocyte precursors (-52.1+/-1.32 mV, n = 43). Analysis of the Itail (using a variable amplitude and duration of the de- and hyperpolarizing prepulses as well as an analysis of the time constant of the membrane currents during voltage steps) showed that the Itail in oligodendrocytes arise from a larger shift of K+ across their membrane than in other cell types. As calculated from the Nernst equation, changes in Vrev revealed significantly larger accumulation of the extracellular K+ concentration ([K+]e) around oligodendrocytes than around astrocytes. The application of 50 mM K+ or hypotonic solution, used to study the effect of cell swelling on the changes in [K+]e evoked by a depolarizing prepulse, produced in astrocytes an increase in [K+]e of 201% and 239%, respectively. In oligodendrocytes, such increases (22% and 29%) were not found. We conclude that K+ tail currents, evoked by a larger accumulation of K+ in the vicinity of the oligodendrocyte membrane, could result from a smaller extracellular space (ECS) volume around oligodendrocytes than around astrocytes. Thus, in addition to the clearance of K+ from the ECS performed by astrocytes, the presence of the K+ tail currents in oligodendrocytes indicates that they might also contribute to efficient K+ homeostasis.

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Extracellular space volume changes in the rat spinal cord produced by nerve stimulation and peripheral injury

Cited by 94 publications

References 37 publications

Extracellular Volume Fraction and Diffusion Characteristics during Progressive Ischemia and Terminal Anoxia in the Spinal Cord of the Rat

Extracellular Volume Fraction and Diffusion Characteristics during Progressive Ischemia and Terminal Anoxia in the Spinal Cord of the Rat

Detection of the neuronal activity occurring caudal to the site of spinal cord injury that is elicited during lower limb movement tasks

Glial depolarization evokes a larger potassium accumulation around oligodendrocytes than around astrocytes in gray matter of rat spinal cord slices

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