Annual Meeting of the Society for Neuroscience edition:32 location:Orlando, Florida, U.S.A. date:November 2-7, 2002
Previous studies revealed an important role for the excitatory neurotransmitter glutamate in adult cortical plasticity. In cats with central retinal lesions, glutamate levels decreased in lesion-affected area 17 but increased in its border zone. We were particularly interested in the role of the NMDA-receptor subunits in topographic map reorganization. Partial determination of the nucleotide sequence of three subunits (NR1, NR2A and NR2B) allowed the construction of cat-specific probes. In situ hybridization did not indicate an altered mRNA expression in area 17 of retinal lesion cats compared to normal cats. Western blot analysis however, using subunit specific antibodies, revealed remarkable changes in protein expression. In normal cats, NR1-expression was higher in central area 17 compared to the peripheral region, while NR2A and NR2B were expressed evenly. In cats with retinal lesions, we found the opposite for NR1 and to a lesser extent NR2B, that is a slightly lower expression in visually deprived, central area 17 versus the non-deprived counterpart. NR2A however showed a remarkable increase in lesion-affected area 17. Control experiments in isolated hemisphere cats (the left optic tract and the corpus callosum were transected, resulting in a right ‘normal’ and a left visually deprived hemisphere) led us to conclude that the lower expression of NR1 and NR2B in lesion-affected area 17 is due to a decrease in neuronal activity, but that NR2A is clearly involved in adult cortical plasticity.