Dependence of cytochrome oxidase activity in the rat lateral geniculate nucleus on retinal innervation

Abstract

Patterns of cytochrome oxidase (CO) activity were examined histochemically in the dorsal lateral geniculate nucleus (LGNd) and retina of pigmented rats. CO staining was not uniform and was distributed in a pattern similar to that of retinal afferents. Portions of the LGNd receiving an exclusively crossed projection were moderately reactive whereas regions receiving an uncrossed or overlapping crossed and uncrossed projection were darkly reactive. The dependence of oxidative metabolic activity in the LGNd on retinal innervation was verified in animals with unilateral enucleation. In adults, chronic monocular enucleation led to a decrease in CO staining in portions of the LGNd deprived of retinal input; in animals enucleated at birth, normal patterns of CO reactivity failed to develop and both LGNds had a more uniform pattern of moderate CO staining. Most neurons in the ganglion cell layer of the retina were moderately reactive for CO. However, there were approximately 3,000 darkly reactive cells, most of which appear to be ganglion cells. The darkly reactive cells were more numerous in the peripheral temporal retina. The laminar pattern of CO staining in the retina was similar to that described previously for carnivores and primates. The most reactive laminae were the inner and outer plexiform layers and the photoreceptor inner segments. Within the inner plexiform layer, sublamina a was more darkly stained than sublamina b. These results suggest that the physiological properties of crossed and uncrossed visual pathways in rats are functionally dissimilar at the level of both the retina and the LGNd.

Retinal ganglion cells of high cytochrome oxidase activity in the rat

“…In normal rats, the cytochrome oxidase reactive cells were fairly evenly distribubed across the entire retina (Fig. 3A), a pattern similar to that described in previous studies [13][14][15]. The great majority of the cells appeared to have relatively largo somata with a diameter varying from 18 to more than 25μm.…”

“…In other words, the larger cells which presumably contain more enzymes can be stained better with the cytochrome oxidase technique. The lack of distinct labeling of cells with small somata supports previous observations that nonganglion cells contribute very little to the cytochrome oxidase activity in the retina under normal condition [13,15]. On the other hand, the selective staining of the large retinal ganglion cells by the cytochrome oxidase method implies that these cells are more active than the smaller ones.…”

“…On the other hand, the selective staining of the large retinal ganglion cells by the cytochrome oxidase method implies that these cells are more active than the smaller ones. If that is the case, the finding of a population of large retinal ganglion cells with high cytochrome oxidase activity in the temporal retina seems to coincide with the observation of a high density of large retinal ganglion cells located in a region in the temporal retina where the midline of the visual field is represented [15,23]. It is also worth noting that many of the large cells located in the temporal crescent probably contribute to the uncrossed retinofugal pathways under both normal and experimental conditions [2,3,11,13,16,20].…”

“…It has long been recognized that the mitochondrial enzyme cytochrome oxidase can be used not only for revealing neurons or brain regions of high oxidative metabolic activity, but can also be used as an marker enzyme for neurons or anatomical entities of the brain with certain special physiological properties [6-9, 12-14,17,18,24-26] In the retina, it has been demonstrated in a variety of mammalian species that the cytochrome oxidase histochemical technique is useful for staining a population of ganglion cells with relabively large somata [13][14][15] However, in most of the cases reported, the dendrites of the retinal ganglion cells especially their secondary and more distal branches can not be visualized using the cytochrome oxidase histochemistry, In view of the fact that the dendritic morphology has become an important feature for studying or classifying ganglion cells [1,4,5,19,22] it is to our interest to find out that whether the cytochrome oxidase histochemical technique can be modified to such an extent that it can stain not only the somata of neurons but also their dendritic arbors. In this study, our attention is given to a populabion of large or alpha-like retinal ganglion cells which is known to constitute only a small percentage of the ontire population of ganglion cells in the rat robina [13,15,23].…”

“…In this study, our attention is given to a populabion of large or alpha-like retinal ganglion cells which is known to constitute only a small percentage of the ontire population of ganglion cells in the rat robina [13,15,23]. The application of the modified cytochrome oxidase histochomical method in studying plastic changes of dendritic arbors of retinal ganglion cells was also discussed.…”