RETINOTOPIC MAP PLASTICITY IN ADULT CAT VISUAL CORTEX IS ACCOMPANIED BY CHANGES IN Ca 2 /CALMODULIN-DEPENDENT PROTEIN KINASE II  AUTOPHOSPHORYLATION G. VAN DEN BERGH, a U. T. EYSEL, b E. VANDENBUSSCHE, c† F. VANDESANDE a AND L. ARCKENS a * a Laboratory of Neuroendocrinology and Immunological Biotechnology, Katholieke Universiteit Leuven, Naamsestraat 59, B-3000 Leuven, Belgium b Department of Neurophysiology, Medical School, Ruhr-Universita ¨t Bochum, Germany c Laboratory of Psychophysiology, Medical School, Katholieke Univer- siteit Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium Abstract—In adult cats, the induction of homonymous binoc- ular central retinal lesions causes a dramatic reorganization of the topographic map in the sensory-deprived region of the primary visual cortex. To investigate the possible involve- ment of the -subunit of the calcium/calmodulin dependent protein kinase type II (CaMKII) in this form of brain plastic- ity, we performed in situ hybridization and Western blotting experiments to analyze mRNA, protein and autophosphory- lation levels of this multifunctional kinase. No differences in the mRNA or protein levels were observed between the cen- tral, sensory-deprived and the peripheral, non-deprived re- gions of area 17 of retinal lesion animals or between corre- sponding cortical regions of normal control animals. Western blotting with an CaMKII threonine-286 phosphorylation- state specific antiserum consistently showed a small, albeit not significant, increase of CaMKII autophosphorylation in the central versus the peripheral region of cortical area 17, and this both in normal subjects as well as in retinal lesion animals with a 3-day post-lesion survival time. In contrast, a post-lesion survival time of 14 days resulted in a CaMKII autophosphorylation level that was four times higher in visu- ally-deprived area 17 than in the non-deprived cortical region. This increased phosphorylation state is not a direct conse- quence of the decrease in visual activity in these neurons, because we would have expected to see a similar change at shorter or longer post-lesion survival times or in the visually deprived visual cortex of animals in which the left optic tract and the corpus callosum were surgically cut. No such changes were observed, leading to the conclusion that the phosphorylation changes observed at 14 days are related to a delayed reorganization of the retinotopic map of the striate cortex. © 2003 IBRO. Published by Elsevier Science Ltd. All rights reserved. Key words: visual cortex, in situ hybridization, Western blot- ting. The visual cortex of adult mammals has the remarkable capability of changing the topography of its representa- tions in response to alterations in sensory input (Gilbert et al., 1990). Undeniably, the induction of restricted homon- ymous central retinal lesions immediately results in re- duced neuronal activity in the sensory-deprived primary visual cortex, followed by an extensive retinotopic map reorganization in ensuing months. This reorganization is characterized by alterations in the receptive fields of the involved neurons. Originally deprived neurons will ulti- mately receive input from the perilesional retina (Kaas et al., 1990; Gilbert and Wiesel, 1992; Chino, 1995; Chino et al., 1995). Eventually, depending on the size of the retinal lesion, the complete visual cortex can again be visually driven. Whereas the geniculate nucleus cannot explain the large extent of cortical reorganization (Eysel et al., 1980, 1981; Eysel, 1982), intracortical mechanisms have been reported to play a major role in this form of retinotopic reorganization (Darian-Smith and Gilbert, 1995). Indeed, Darian-Smith and Gilbert (1994) observed terminal sprout- ing of intrinsic long-range horizontally projecting axons, albeit only from 8 months post-lesion on. On the other hand, as early as a few hours after the induction of the retinal lesions, changes in receptive field size and position could be observed, suggesting the involvement of a strengthening mechanism of previously existing, sub- threshold synapses in the initial phase of cortical plasticity (Chino et al., 1992). The molecular basis of this retinotopic reorganization remains hitherto largely elusive, but the above-mentioned potentiation of already existing synapses might resemble other forms of synaptic plasticity, like hippocampal long- term potentiation (LTP, Bliss and Collingridge, 1993; Malenka, 1994). A key player for the induction of long-term synaptic potentiation is the multifunctional calcium/calmod- ulin-dependent protein kinase type II (CaMKII), a serine/ threonine protein kinase, abundantly present in post-syn- aptic densities and activated by Ca 2+ and calmodulin (Kennedy et al., 1983). Indeed, the presence of the CaMKII -subunit (Malinow et al., 1989; Silva et al., 1992) as well as autophosphorylation of CaMKII at threonine 286 (Thr 286 ; Giese et al., 1998) appear to be required for LTP. This autophosphorylation results in a calcium-independent activity of the kinase (Miller and Kennedy, 1986). † Deceased December 11, 2002. *Corresponding author. Tel: +32-16-32-3951; fax: +32-16-32-4263. E-mail address: lut.arckens@bio.kuleuven.ac.be. (L. Arckens). Abbreviations: CaMKII, Ca 2+ /calmodulin dependent protein kinase type II subunit ; dLGN, dorsal lateral geniculate nucleus; EDTA, ethylenediaminetetraacetic acid; GAPDH, glyceraldehyde-3-phos- phate dehydrogenase; LTP, long-term potentiation; PLLS, posterior lateral lateral suprasylvian area; PMLS, posterior medial lateral supra- sylvian area; Thr 286 , threonine residue 286. Neuroscience 120 (2003) 133–142 0306-4522/03$30.00+0.00 © 2003 IBRO. Published by Elsevier Science Ltd. All rights reserved. doi:10.1016/S0306-4522(03)00291-4 133