Cytochrome oxidase activity in the lateral geniculate nucleus of postnatal rats.

We have studied the cytochrome oxidase activity and its pattern of distribution in the dorsal lateral geniculate nucleus of the rat during postnatal development. Between the 1st and the 8th postnatal days, the geniculate nucleus is seen to have a homogeneous enzymatic pattern with high neuronal density and moderately reactive neuropil. On the 15th postnatal day, different levels of neuronal enzymatic activity are found, and adult morphology is attained as of the 21st. The densitometric study has revealed that moderate and lightly reactive neurons are predominant between the 1st and the 8th postnatal days, whereas dark neurons are more numerous and optical density maximum on the 15th postnatal day. No variation in the enzymatic pattern was observed between the 21st and the 42nd days.