RESUMO
We used immunohistochemistry to localize vesicular glutamate transporters VGLUT1 and VGLUT2 in the rat lateral geniculate nucleus. The lateral geniculate nucleus is intensely immunoreactive for both transporters. Monocular eye removal abolished staining for VGLUT2 in a pattern corresponding to the distribution of terminals from the missing eye, without affecting distribution of VGLUT1 immunoreactivity. These data indicate retinal ganglion cells are the source of VGLUT2-containing synapses in the lateral geniculate nucleus.
Assuntos
Proteínas de Transporte/ultraestrutura , Corpos Geniculados/citologia , Proteínas de Membrana Transportadoras , Células Ganglionares da Retina/ultraestrutura , Sinapses/ultraestrutura , Proteínas de Transporte Vesicular , Animais , Proteínas de Transporte/metabolismo , Enucleação Ocular , Corpos Geniculados/metabolismo , Corpos Geniculados/ultraestrutura , Imuno-Histoquímica , Ratos , Ratos Long-Evans , Células Ganglionares da Retina/metabolismo , Sinapses/metabolismo , Proteína Vesicular 1 de Transporte de Glutamato , Proteína Vesicular 2 de Transporte de GlutamatoRESUMO
The transition metal zinc is an essential dietary constituent that is believed to serve an important intercellular signaling role at certain excitatory synapses in the central nervous system. In the present study, we used histochemical techniques to investigate the distribution of synaptic zinc during postnatal development of retinogeniculate projections in rats. From postnatal day (P) 1 until P-21, the pattern of zinc histochemical staining in the dorsal lateral geniculate nucleus (LGNd) precisely matched the distribution of axon terminals from the ipsilateral eye that were labeled by anterograde transport of horseradish peroxidase. Regions of the LGNd that contained only crossed axons were devoid of zinc staining. Abnormalities in the distribution of uncrossed retinogeniculate projections in albino versus pigmented rats were paralleled by identical variations in localization of synaptic zinc. Unilateral enucleation on P-10 was followed within 5 days by loss of zinc staining in the LGNd ipsilateral to the removed eye without affecting staining in the contralateral nucleus. Finally, the ability to detect zinc histochemically in the LGNd ceased at approximately P-24. These findings provide evidence that zinc is sequestered within synaptic boutons of a subpopulation of retinal ganglion cells whose axons terminate on the ipsilateral side of the brain. The duration of zinc staining overlaps with the major period of axonal remodeling in the LGNd, suggesting that synaptically released zinc may play a role in postnatal refinement of retinogeniculate projections.
Assuntos
Lateralidade Funcional/fisiologia , Corpos Geniculados/crescimento & desenvolvimento , Terminações Pré-Sinápticas/metabolismo , Retina/crescimento & desenvolvimento , Vias Visuais/crescimento & desenvolvimento , Zinco/metabolismo , Fatores Etários , Albinismo/metabolismo , Albinismo/patologia , Albinismo/fisiopatologia , Animais , Animais Recém-Nascidos , Padronização Corporal/fisiologia , Enucleação Ocular/efeitos adversos , Corpos Geniculados/citologia , Corpos Geniculados/metabolismo , Histocitoquímica/métodos , Plasticidade Neuronal/fisiologia , Terminações Pré-Sinápticas/ultraestrutura , Ratos , Ratos Long-Evans/anatomia & histologia , Ratos Long-Evans/crescimento & desenvolvimento , Ratos Long-Evans/metabolismo , Retina/citologia , Retina/metabolismo , Vias Visuais/citologia , Vias Visuais/metabolismoRESUMO
Histochemical staining was used to localize zinc-sequestering terminals in somatosensory barrel cortex of normal mice and mice subjected to tactile deprivation by simple whisker trimming from birth. In normal mice, density of synaptic zinc was highest in laminae I, II and V, intermediate in laminae III and VI, and lowest in lamina IV barrel hollows. Whisker trimming from birth led to increased density of synaptic zinc specifically within deprived barrel hollows.
