[Histochemical studies on the change of nitric oxide synthetase in lateral geniculate nucleus of monocular deprived kittens].

OBJECTIVE: To observe the change of nitric oxide synthetase (NOS) in lateral geniculate nucleus of normal and monocular deprived kittens and to discuss the role of nitric oxide in the etiopathology of amblyopia. METHODS: The distribution of nitric oxide synthetase in lateral geniculate nucleus (LGN) of normal and monocular deprived kittens had been studied by using nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemical method (NDP). RESULTS: In normal kittens, NOS positive cells were not seen in any lamina of LGN, but NOS positive fibers were discovered. In monocular deprived kittens, NOS positive fibers were seen in every layers of LGN, in the nondeprived laminae of LGN there was strip-shaped distribution of NOS positive cells, and in the deprived laminae the NOS positive cells were occasionally seen. CONCLUSION: NOS might act as a new class of neurotransmitter and be involved in the formation of emblyopia.

Pattern of ocular dominance columns and cytochrome oxidase activity in a macaque monkey with naturally occurring anisometropic amblyopia.

Unilateral eyelid suture, a model for amblyopia induced by congenital cataract, produces shrinkage of the deprived eye's ocular dominance columns in the striate cortex. Loss of geniculocortical projections are thought to account for the poor vision in the amblyopic eye. It is uncertain whether ocular dominance columns become shrunken in other forms of amblyopia. We examined the striate cortex in a pigtailed macaque with natural anisometropia discovered at age 5 months. Amblyopia in the left eye was documented at 1 year by behavioral testing. At age 6 years, the left eye was injected with [3H]proline and the striate cortex was processed for autoradiography and cytochrome oxidase (CO). The ocular dominance columns in layer IVc labelled with [3H]proline were normal. CO staining showed a novel pattern of thin dark bands in layer IV. These bands occupied the core zones at the center of the ocular dominance columns. Their appearance resulted from relative loss of CO activity along the borders of the ocular dominance columns, regions specialized for binocular processing. These findings indicate that not all forms of amblyopia are accompanied by shrinkage of ocular dominance columns. The unusual pattern of CO staining in layer IVc reflected a subtle alteration in metabolic activity which may have resulted from impairment of binocular function in anisometropic amblyopia.