Time course of dorsolateral geniculate nucleus plasticity in adult monkeys with laser-induced retinal lesions.

We studied changes in the expression of growth-associated protein 43 (GAP43), glial fibrillary acidic protein (GFAP), and calcium-binding proteins (calbindin [Cb] and parvalbumin [Pv]) in the dorsal lateral geniculate nucleus (dLGN) of four capuchin monkeys with laser-induced retinal lesions. The lesions were generated with the aid of a neodymium-YAG dual-frequency laser with shots of different intensity and at different survival time in each animal. The expression of these proteins in the layers of the dLGN was evaluated by performing histodensitometry of coronal sections throughout the nucleus. High-power laser shots administered at the border of the optic disc (OD)-injured fibers resulted in large scotomas. These lesions produced a devastating effect on fibers in this passage, resulting in large deafferentation of the dLGN. The time course of plasticity expressed in this nucleus varied with the degree of the retinal lesion. Topographically, corresponding portions of the dLGN were inferred by the extent of the ocular dominance column revealed by cytochrome oxidase histochemistry in flattened preparations of V1. In the region representing the retinal lesion, the expression of GFAP, GAP43, Pv, and Cb increased and decreased in the corresponding dLGN layers shortly after lesion induction and returned to their original values with different time courses. Synaptogenesis (indicated by GAP43 expression) appeared to be increased in all layers, while "cleansing" of the glial-damaged region (indicated by GFAP expression) was markedly greater in the parvocellular layers, followed by the magnocellular layers. Schematic drawings of optic discs laser lesions and of series of coronal sections of the dLGN, in three monkeys, depicting the areas of the nucleus deafferented by the lesions.

Time course of cytochrome oxidase blob plasticity in the primary visual cortex of adult monkeys after retinal laser lesions.

We studied the time course of changes of cytochrome oxidase (CytOx) blob spatial density and blob cross-sectional area of deprived (D) and nondeprived (ND) portions of V1 in four capuchin monkeys after massive and restricted retinal laser lesions. Laser shots at the border of the optic disc produced massive retinal lesions, while low power laser shots in the retina produced restricted retinal lesions. These massive and restricted retinal lesions were intended to simulate glaucoma and diabetic retinopathy, respectively. We used a Neodymium-YAG dual frequency laser to make the lesions. We measured Layer III blobs in CytOx-reacted tangential sections of flat-mounted preparations of V1. The plasticity of the blob system and that of the ocular dominance columns (ODC) varied with the degree of retinal lesions. We found that changes in the blob system were different from that of the ODC. Blob sizes changed drastically in the region corresponding to the retinal lesion. Blobs were larger and subjectively darker above and below the non deprived ODC than in the deprived columns. With restricted lesions, blobs corresponding to the ND columns had sizes similar to those from non-lesioned areas. In contrast, blobs corresponding to the deprived columns were smaller than those from nonlesioned areas. With massive lesions, ND blobs were larger than the deprived blobs. Plastic changes in blobs described here occur much earlier than previously described.

Differential expression of Zif268 and c-Fos in the primary visual cortex and lateral geniculate nucleus of normal Cebus monkeys and after monocular lesions.

The transcription factors c-Fos and Zif268 have been used as markers of neuronal activity, and they also have been implicated in neuronal plasticity. In this study, we investigated the expression of c-Fos and Zif268 proteins in the lateral geniculate nucleus (LGN) and in the cortical primary visual area (V1) of normal adult Cebus apella monkeys and in animals with monocular lesions. In the LGN, the reaction for c-Fos showed immunopositive cells in both magnocellular (M) and parvocellular (P) layers; however, the label was heavier in P layers. In animals that suffered monocular lesions, the immunocytochemistry for c-Fos showed more labeling in layers related to the normal eye compared with those of the lesioned eye. No specific label was observed after the reaction for Zif268 in the LGN. In V1, the reaction for both Zif268 and c-Fos showed a pattern of lamination in which heavier labeling was found in layers 2/3, 4A, 4C, and 6. After monocular lesions, we observed a clear pattern of ocular dominance columns in V1 for both c-Fos and Zif268, in which the columns related to the normal eye are more heavily labeled than those related to the lesioned eye. This pattern is more evident in layer 4C after c-Fos reaction, whereas, after Zif268, it is more clearly observed in layers 2/3. These results suggest that, in addition to be regulated by functional activity, these transcription factors are involved in different processes during cortical reorganization.