Reducing excessive GABA-mediated tonic inhibition promotes functional recovery after stroke

Journal name:
Nature
Volume:
468,
Pages:
305–309
Date published:
DOI:
doi:10.1038/nature09511
Received
Accepted
Published online

Stroke is a leading cause of disability, but no pharmacological therapy is currently available for promoting recovery. The brain region adjacent to stroke damage—the peri-infarct zone—is critical for rehabilitation, as it shows heightened neuroplasticity, allowing sensorimotor functions to re-map from damaged areas1, 2, 3. Thus, understanding the neuronal properties constraining this plasticity is important for the development of new treatments. Here we show that after a stroke in mice, tonic neuronal inhibition is increased in the peri-infarct zone. This increased tonic inhibition is mediated by extrasynaptic GABAA receptors and is caused by an impairment in GABA (γ-aminobutyric acid) transporter (GAT-3/GAT-4) function. To counteract the heightened inhibition, we administered in vivo a benzodiazepine inverse agonist specific for α5-subunit-containing extrasynaptic GABAA receptors at a delay after stroke. This treatment produced an early and sustained recovery of motor function. Genetically lowering the number of α5- or δ-subunit-containing GABAA receptors responsible for tonic inhibition also proved beneficial for recovery after stroke, consistent with the therapeutic potential of diminishing extrasynaptic GABAA receptor function. Together, our results identify new pharmacological targets and provide the rationale for a novel strategy to promote recovery after stroke and possibly other brain injuries.

At a glance

Figures

  1. Increased tonic inhibition in peri-infarct cortex.
    Figure 1: Increased tonic inhibition in peri-infarct cortex.

    a, Images showing the peri-infarct recording site. Whole-cell patch-clamp recordings were made from post-stroke brain slices, within 200μm of the infarct (top left; image under 2× magnification), from layer-2/3 (top right; 10×) pyramidal neurons (bottom panels; 40×). b, Box plot (boxes, 25–75%; whiskers, 10–90%; lines, median) showing significantly increased tonic inhibition in peri-infarct cortex (asterisk, P<0.05; see Supplementary Fig. 2 for further analyses). c, d, Representative traces showing tonic inhibitory currents in control and peri-infarct neurons, respectively. Tonic currents were revealed by the shift in holding currents after blocking all GABAA receptors with gabazine (>100μM). Cells were voltage clamped at +10mV.

  2. Impairment in GABA transport and effect of blocking [agr]5-GABAA receptors after stroke.
    Figure 2: Impairment in GABA transport and effect of blocking α5-GABAA receptors after stroke.

    a, Blocking GAT-1 (NO-711) produced a higher percentage increase in Itonic after stroke; combined blockade of GAT-1 and GAT-3/GAT-4 (NO-711 plus SNAP-5114) produced a substantial Itonic increase in controls but only an increase equivalent to blocking GAT-1 alone after stroke. b, c, Itonic in sequential drug applications. Note the lack of response to SNAP-5114 application in the post-stroke slice. d, L655,708 reduced Itonic. e, L655,708 significantly decreased Itonic after stroke. f, Drug treatment reverted post-stroke Itonic to near-control level. *, P<0.05; NS, not significant; bar graphs represent mean±s.e.m.

  3. Behavioural recovery after stroke with L655,708 treatment and in Gabra5-/- and Gabrd-/- animals
    Figure 3: Behavioural recovery after stroke with L655,708 treatment and in Gabra5/and Gabrd/animals

    ac, L655,708 treatment starting from 3 days after stroke resulted in a dose-dependent improvement in functional recovery after stroke. df, Gabra5−/− and Gabrd−/− mice also showed decreased motor deficits after stroke. Functional recovery was assessed with forelimb (a, d) and hindlimb foot faults (b, e), and on forelimb asymmetry (c, f). Low-dose L655,708 = 200μgkg−1day−1 per animal; high-dose L655,708 = 400μgkg−1day−1 per animal. Pre-op, pre-operation. Data are mean±s.e.m. , P0.001 stroke plus vehicle versus sham; *,P0.05; **,P0.01; ***,P0.001 versus stroke plus vehicle.

  4. Inflection point in L655,708 treatment effect on infarct size.
    Figure 4: Inflection point in L655,708 treatment effect on infarct size.

    ad, Representative Nissl-stained sections at 7 days after stroke from stroke plus vehicle treatment (a), stroke plus L655,708 treatment starting at the time of stroke (b) and stroke plus L655,708-treatment starting from 3 days post-insult (c). Quantification of the stroke volume is shown in panel d. Data are mean±s.e.m. for n = 4 per group; * = P0.05.

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Author information

  1. These authors contributed equally to this work.

    • Andrew N. Clarkson &
    • Ben S. Huang

Affiliations

  1. Department of Neurology, The David Geffen School of Medicine at UCLA, 635 Charles Young Drive South, Los Angeles, California 90095, USA

    • Andrew N. Clarkson,
    • Ben S. Huang,
    • Sarah E. MacIsaac,
    • Istvan Mody &
    • S. Thomas Carmichael
  2. Interdepartmental PhD Program for Neuroscience, The David Geffen School of Medicine at UCLA, 635 Charles Young Drive South, Los Angeles, California 90095, USA

    • Ben S. Huang &
    • Istvan Mody
  3. Department of Physiology, The David Geffen School of Medicine at UCLA, 635 Charles Young Drive South, Los Angeles, California 90095, USA

    • Istvan Mody
  4. Present address: Departments of Psychology and Anatomy and Structural Biology, University of Otago, PO Box 913, Dunedin 9013, New Zealand.

    • Andrew N. Clarkson

Contributions

A.N.C. performed the behavioural, histological and immunohistochemical studies; B.S.H. carried out the electrophysiological experiments; and S.E.M. performed the immunohistochemical and western blot work. A.N.C., B.S.H., I.M. and S.T.C. designed the experiments, analysed data, prepared figures and wrote the manuscript.

Competing financial interests

The authors declare no competing financial interests.

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