DARK-REARING CHANGES DENDRITIC MICROTUBULE-ASSOCIATED PROTEIN-2 (MAP2) BUT NOT SUBPLATE NEURONS IN CAT VISUAL-CORTEX

Sensory-dependent modification of cortical morphology is one component of the cortical plasticity that occurs during the critical period for ocular dominance changes. In this study, we used dark-rearing to exam ine the sensory dependency of subplate neuron death and the quantity o f microtubule-associate protein 2 (MAP2)-positive dendrites. Kittens r eared in total darkness until the peak of the critical period had fewe r laterally extended MAP2-positive dendrites than age-matched normal k ittens. This reduction was found in layer TV but not in layer V. Subse quent exposure to light for 10 days after dark-rearing was sufficient to bring the number of MAP2-positive dendrites to the normal level. Co ntrarily, dark-rearing did not prevent subplate neurons from dying. Ex posure to light after dark-rearing did not increase the number of pote ntial dying neurons. These results show that the quantity of MAP2-posi tive dendrites is sensory-dependent; however, the death of the subplat e neurons is not. Therefore, the death of subplate neurons is probably not directly involved in sensory-dependent modifications of synaptic connections. The possible involvement-of laterally extended MAP2-dendr ites in visual plasticity is discussed. (C) 1995 Wiley-Liss, Inc.