Widespread up-regulation of N-methyl-D-aspartate receptors after focal photothrombotic lesion in rat brain Meishu Que a, * , Klaus Schiene b , Otto W. Witte b , Karl Zilles a, c a C. & O. Vogt Institute of Brain Research, University of Du Èsseldorf, P.O. Box101007, D-40225 Du È sseldorf, Germany b Department of Neurology, University of Du Èsseldorf, P.O. Box 101007, D-40225 Du È sseldorf, Germany c Institute of Medicine, Research Center Ju È lich, D-52425 Ju È lich, Germany Received 26 May 1999; received in revised form 14 June 1999; accepted 12 July 1999 Abstract Following focal brain lesions, complex adaptive processes take place in remote intact areas. The present study examines changes in NMDA (N-methyl-D-aspartate), AMPA ((^)-a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) and kainate receptors following focal photothrombotic ischemic lesions using quantitative receptor autoradiogra- phy. Increases in binding density of NMDA receptors were seen in both hemispheres for up to 30 days. In the contral- ateral hemisphere, this increase of NMDA receptors occurred as early as 4 h after lesion whereas it appeared with a delay for 14 days on the lesioned side. Binding density of [ 3 H]AMPA and [ 3 H]kainate was unchanged. We suggest that the translational process is differentially regulated by spreading depressions. The delayed up-regulation of NMDA receptor binding on the lesioned side may be due to a translation block similar to that previously described for GABA A receptor subunits. q 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Focal ischemia; N-Methyl-D-aspartate; (^)-a-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid and kainate receptors; Disturbed receptor balance; Rat brain Following focal brain lesions, complex adaptive processes take place in the brain. Cortical disinhibition is widespread after focal photothrombotic lesion [1]. This is associated with an alteration of the balance between excita- tory and inhibitory amino acid receptors in the cerebral cortex ischemic lesion [12,14]. Electrophysiological experi- ments recently indicated an additional and probably inde- pendent alteration of excitatory transmission following focal brain lesions [3]. In the present study, we analyzed changes in the binding densities of NMDA (N-methyl-d- aspartate), AMPA ((^)-a-amino-3-hydroxy-5-methylisox- azole-4-propionic acid) and kainate receptors in areas surrounding a photothrombotic lesion and in cortical regions remote from the lesion in both hemispheres. Adult male Wistar rats (280±310 g, n  36) were anesthetized with 1.5±2% halothane in a mixture of O 2 /N 2 . An optic ®ber bundle, mounted on a cold light source (Schott KL 1500, Germany), was positioned exactly 4 mm posterior to bregma and 4 mm lateral to midline. The parie- tal cortex (hind limb representation area, HL) was illumi- nated for 20 min. Immediately following the onset of illumination, Rose Bengal (Aldrich Chemie, Steinheim, Germany, 1.3 mg/100 g body weight) was injected through a catheter inserted into the femoral vein, thus causing a photothrombotic lesion in the illuminated area. After differ- ent postlesional survival times (4 h, 3, 7, 14 and 30 days), the brains were removed and frozen in isopentane at 250 to 2708C. Sham-operated age-matched animals were used as controls (n  5). Frontal sections (10 mm) were cut in a cryostat at 2208C. NMDA, AMPA and kainate receptors were studied with speci®c ligands: [ 3 H]MK-801 (dizocilpine), [ 3 H]AMPA and [ 3 H]kainate, respectively. The glass-mounted cryostat sections were preincubated in the speci®c buffers for remov- ing endogenous ligands (3 £ 5 min at 48C). For demonstrat- ing the optimal binding of [ 3 H]MK-801 to NMDA receptors, the assay was performed in a magnesium- and zinc-free solution (5 mM Tris±HCl buffer, pH 7.5) in the presence of 30 mM glycine and 50 mM spermidine with 5 nM [ 3 H]MK-801 at 228C for 60 min. AMPA receptors were labeled with 10 nM [ 3 H]AMPA in 50 mM Tris-acetate buffer (pH 7.2, containing 100 mM potasium thiocyanate) for 60 min at 48C. For identifying kainate receptors, sections Neuroscience Letters 273 (1999) 77±80 0304-3940/99/$ - see front matter q 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S0304-3940(99)00598-4 www.elsevier.com/locate/neulet * Corresponding author. Tel.: 149-211-81-12798; fax: 149-211- 81-12336. E-mail address: que@hirn.uni-duesseldorf.de (M. Que)