Brain Research 962 (2003) 199–206 www.elsevier.com / locate / brainres Research report Retinal lesions affect extracellular glutamate levels in sensory-deprived and remote non-deprived regions of cat area 17 as revealed by in vivo microdialysis a ,1 a a a b Ying Qu , Ann Massie , Estel Van der Gucht , Lieselotte Cnops , Erik Vandenbussche , c a a, * Ulf T. Eysel , Frans Vandesande , Lutgarde Arckens a Laboratory of Neuroendocrinology and Immunological Biotechnology, Katholieke Universiteit Leuven, Naamsestraat 59, B-3000 Leuven, Belgium b Laboratory of Neuro-psychology, Medical School, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium c ¨ Department of Neurophysiology, Medical School, Ruhr-Universitat Bochum, D-44770 Bochum, Germany Accepted 12 November 2002 Abstract This study aimed at gaining insight into the role of the excitatory neurotransmitter glutamate in topographic map reorganization in the sensory systems of adult mammals after restricted deafferentations. Hereto, in vivo microdialysis was used to sample extracellular glutamate from sensory-deprived and non-deprived visual cortex of adult awake cats 18 to 53 days after the induction of restricted binocular retinal lesions, and in topographically corresponding cortical regions of control animals. A microbore HPLC-ED method was applied for the analysis of the microdialysates. In normal subjects, the visual cortex subserving central and peripheral vision showed similar extracellular fluid glutamate concentrations. In contrast, in animals with homonymous central retinal lesions, the extracellular glutamate concentration was significantly lower in central, sensory-deprived cortex compared to peripheral, non-deprived cortex. Compared to control regions in normal subjects, glutamate decreased in the extracellular fluid of deprived cortex but increased significantly in remote non-deprived visual cortex. These results not only suggest an activity-dependent regulation of the glutamate levels in visual cortex but also imply a role for perilesional cortical regions in topographic map reorganization following sensory deafferentation.  2002 Elsevier Science B.V. All rights reserved. Theme: Sensory systems Topic: Visual cortex: striate Keywords: In vivo microdialysis; Brain; Sensory deafferentation; Glutamate; Visual system; Plasticity 1. Introduction responsiveness to visual stimulation through the acquisi- tion of new receptive fields receiving inputs from retinal In the visual system of adult cats and monkeys, binocu- locations adjacent to the lesions [6,13,14,16]. Proposed lar retinal lesions produce a sensory-deprived zone in the structural mechanisms for such a reorganization of cortical corresponding region of the primary visual cortex in which topography include alterations in the effectiveness of neurons no longer respond to visual stimuli. Within a few previously existing connections and the growth of new months, the cells in the lesion-affected cortical area regain connections. However, the molecular mechanisms underly- ing this reorganization of the adult brain are poorly understood. *Corresponding author. Tel.: 132-16-323-926; fax: 132-16-324-263. Several neurotransmitters and neuromodulators have E-mail addresses: quying@mail.nih.gov (Y. Qu), already been implicated in adult brain plasticity [1,3– lut.arckens@bio.kuleuven.ac.be (L. Arckens). 1 5,7,18,26,33]. Indeed, the involvement of the major inhib- Present address: Section of Brain Physiology and Metabolism, National itory neurotransmitter gamma-amino-butyric acid in corti- Institute on Aging, NIH, Building 10, Room 6N202, Bethesda, MD 20892, USA. Tel.: 11-301-594-3134; fax: 11-301-402-0074. cal reorganization has been demonstrated in visual and 0006-8993 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0006-8993(02)04047-7