Nitrergic dendrites in the superficial layers of the rat superior colliculus: retinal afferents and alternatively spliced isoforms in normal and deafferented animals.
The superficial layers of the rat superior colliculus (sSC) receive innervation from the retina and include nitrergic neurons. We have shown previously that in sSC, eye enucleation reduces NADPH diaphorase staining considerably in all but the most proximal dendrites of nitrergic neurons. We have used immunocytochemistry for neuronal nitric oxide synthase (nNOS) at light and electron microscopic levels and bilateral eye enucleation with varied survival times to determine the regulatory changes imposed by the direct and indirect loss of retinal input on apparent nNOS amount and subcellular distribution. In addition, we have used SDS-PAGE and immunoblotting to test alternatively spliced isoforms in normal and deafferented animals. Our results show that unambiguously identified retinal terminals contact nitrergic neurons. In normal dendrites, nNOS immunoreactivity was distributed almost completely within the cytoplasm of the dendrite and along the postsynaptic membrane at synaptic junctions, in association with endoplasmic reticulum, ribosomes and external mitochondrial membranes. In contrast, nNOS labeling was greatly reduced in sSC deprived of retinal projections, and could only be observed in association with mitochondrial membranes and postsynaptic densities. Immunoblots of the soluble fraction from sSC revealed a surprisingly high proportion of the beta isoform with respect to the alpha counterpart in normal colliculi, suggesting an increase in isoform proportion after enucleation, or at least maintenance of the same proportion. It is suggested that ultrastructural alterations observed in sSC cells of enucleated animals may be consequent to plastic reactions of the sSC cells in response to the removal of retinal afferents.
Batista
Claudia M C
CM
Departamento de Histologia e Embriologia, ICB, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Carneiro
Kátia
K
de Bittencourt-Navarrete
Ruben Ernesto
RE
Soares-Mota
Marcia
M
Cavalcante
Leny A
LA
Mendez-Otero
Rosalia
R
D000344:Afferent Pathways / Q000201:enzymology / Q000648:ultrastructure; D000818:Animals; D003712:Dendrites / Q000201:enzymology* / Q000648:ultrastructure; D007527:Isoenzymes / Q000032:analysis / Q000096:biosynthesis; D026602:Nitrergic Neurons / Q000201:enzymology* / Q000648:ultrastructure; D019001:Nitric Oxide Synthase / Q000032:analysis* / Q000096:biosynthesis; D052248:Nitric Oxide Synthase Type I; D051381:Rats; D012160:Retina / Q000201:enzymology* / Q000648:ultrastructure; D013477:Superior Colliculi / Q000201:enzymology* / Q000648:ultrastructure
D007527:Isoenzymes; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat