Widespread and long-lasting alterations in GABA(A)-receptor subtypes after focal cortical infarcts in rats: mediation by NMDA-dependent processes

J Cereb Blood Flow Metab. 2002 Dec;22(12):1463-75. doi: 10.1097/01.WCB.0000034149.72481.BD.

Abstract

Impairment of inhibitory neurotransmission has been reported to occur in widespread, structurally intact brain regions after focal ischemic stroke. These long-lasting alterations contribute to the functional deficit and influence long-term recovery. Inhibitory neurotransmission is primarily mediated by gamma-aminobutyric acid (GABA)A receptors assembled of five subunits that allow a variety of adaptive changes. In this study, the regional distribution of five major GABA(A)-receptor subunits (alpha1, alpha2, alpha3, alpha5, and gamma2) was analyzed immunohistochemically 1, 7, and 30 days after photochemically induced cortical infarcts. When compared with sham-operated controls, a general and regionally differential reduction in immunostaining was found within the cortex, hippocampus, and thalamus of both hemispheres for almost all subunits. Within ipsilateral and contralateral neocortical areas, a specific pattern of changes with a differential decrease of subunits alpha1, alpha2, alpha5, and gamma2 and a significant upregulation of subunit alpha3 was observed in the contralateral cortex homotopic to the infarct. This dysregulation was most prominent at day 7 and still present at day 30. Interestingly, a single application of the noncompetitive N-methyl-D-aspartate-receptor antagonist MK-801 during lesion induction completely blocked these bihemispheric alterations. Cortical spreading depressions induced by topical application of KCl do not change GABA(A)-receptor subunit expression. As alterations in subtype distribution crucially influence inhibitory function, ischemia-induced modifications in GABA(A)-receptor subtype expression may be of relevance for functional recovery after stroke.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cerebral Infarction / metabolism*
  • Cerebral Infarction / pathology
  • Cortical Spreading Depression
  • Dizocilpine Maleate / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Functional Laterality
  • Hippocampus / metabolism
  • Intracranial Thrombosis / metabolism
  • Intracranial Thrombosis / pathology
  • Male
  • Neocortex / metabolism
  • Neocortex / pathology
  • Rats
  • Rats, Wistar
  • Receptors, GABA-A / metabolism*
  • Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Thalamus / metabolism

Substances

  • Excitatory Amino Acid Antagonists
  • Receptors, GABA-A
  • Receptors, N-Methyl-D-Aspartate
  • Dizocilpine Maleate