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 examine the sensory dependency of subplate neuron death and the quantity of microtubule-associate protein 2 (MAP2)-positive dendrites. Kittens reared in total darkness until the peak of the critical period had fewer laterally extended MAP2-positive dendrites than age-matched normal kittens. This reduction was found in layer IV but not in layer V. Subsequent exposure to light for 10 days after dark-rearing was sufficient to bring the number of MAP2-positive dendrites to the normal level. Contrarily, dark-rearing did not prevent subplate neurons from dying. Exposure to light after dark-rearing did not increase the number of potential dying neurons. These results show that the quantity of MAP2-positive dendrites is sensory-dependent; however, the death of the subplate 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-dendrites in visual plasticity is discussed.