In adult cats, the induction of homonymous binocular 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 involvement of the a-subunit of the calcium/calmodulin dependent protein kinase type II (alphaCaMKII) in this form of brain plasticity, we performed in situ hybridization and Western blotting experiments to analyze mRNA, protein and autophosphorylation levels of this multifunctional kinase. No differences in the mRNA or protein levels were observed between the central, sensory-deprived and the peripheral, non-deprived regions of area 17 of retinal lesion animals or between corresponding cortical regions of normal control animals. Western blotting with an alphaCaMKII threonine-286 phosphorylation-state specific antiserum consistently showed a small, albeit not significant, increase of aCaMKII 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 aCaMKII autophosphorylation level that was four times higher in visually-deprived area 17 than in the non-deprived cortical region. This increased phosphorylation state is not a direct consequence 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. (C) 2003 IBRO. Published by Elsevier Science Ltd. All rights reserved.