[Golgi-Cox study of the distribution of dendritic spines in the cerebral cortex of the kitten. Part 1. The first 15 days of the postnatal period].

In order to study quantitatively the development of dendritic spines of pyramidal neurones, the suprasylvian cortex of kittens (1 to 15 days of age) was fixed and embedded by the Golgi-Cox (Sholl) method. The spines seen at different cortical levels were counted to establish their distribution along apical and basal dendrites. Disposition of spine contacts varied during the first month of post-natal cortical development. three periods were established in relation to the morphological growth of neurones. The first period(days 6 to 9), showed better defined layers and differentiation of spines in areas of maximal density. The third period (days 10 to 15) was defined by a remarkable enlargment of cellular processes, neural stratification and spinal distribution comparable to that of adult animals, although with a smaller number of spines. It is concluded that the organization of dendritic spines is closely related to neuronal development, coinciding with the initiation of cortical afferent systems.