DISTRIBUTION OF CYTOCHROME-OXIDASE AND PARVALBUMIN IN THE PRIMARY VISUAL-CORTEX OF THE ADULT AND NEONATE MONKEY, CALLITHRIX-JACCHUS

The anatomical distributions of the mitochondrial enzyme cytochrome ox idase (CO) and of the calcium binding protein parvalbumin (PV) were st udied in the striate cortex of adult and neonate New World monkeys (Ca llithrix jacchus). In the adult marmoset, both proteins were found in laminar arrangements similar to those described for the macaque monkey , with prominent bands of PV-like immunoreactive (PV-LI) puncta in lay ers TV and IIIb, and fairly evenly distributed PV-LI nonpyramidal neur ons. Furthermore, the pattern of CO activity in area 17 of the neonate marmoset was almost identical to the CO pattern described in neonate macaque and squirrel monkeys. It came, therefore, as a surprise to fin d that the adult pattern of PV-like immunoreactivity (PV-LI) in the ma rmoset striate cortex arises from a neonatal pattern strikingly differ ent from that seen in any developmental stage of the macaque, or in an y other mammal studied so far. In the deep layers IV through VI of the neonate marmoset, a large number of PV-LI neurons was stained in band like patterns, their number in layers IV and V exceeding the number of PV-LI neurons present in these layers of the adult marmoset area 17. Staining of layers TV and VI was restricted to area 17 and involved no npyramidal cells and their processes. The stained band of layer V, in contrast, continued throughout most of the neocortex. In area 17, an e stimated 10 to 20% of the stained cells in layer V exhibited pyramidal shapes. The findings show that the expression of PV by visual cortica l cells occurs before birth and suggest that the comparatively early o nset of PV expression is not dependent on the onset of textured vision . The exuberant number of stained cells in some layers, and particular ly the staining of pyramidal cells, in the neonate marmoset, suggest t hat a considerable number of cells possesses the stainability for PV-L I only transiently, i.e., in the marmoset, these cells have a specific demand for parvalbumin during this phase of their development.