Glutamate containing neurons in the cat superior colliculus revealed by immunocytochemistry

Abstract

Glutamate is the probable neurotransmitter of both retinal and cortical afferents to the cat superior colliculus (SC). The present study shows that glutamate is also contained in many postsynaptic neurons in SC. The distribution, morphology, and ultrastructure of neurons in SC were examined using glutamate antibody immunocytochemistry. Labeled cells were widely distributed throughout, but a specific laminar pattern was evident. Relatively few cells were found in the zonal and upper superficial gray layers (SGL). A dense band of intensely labeled neurons was found within the deep superficial gray and upper optic layers. Many cells were also labeled in the deeper layers. Labeled cells had varied sizes and morphologies. Soma diameters ranged from 9-67 /xm, with a mean of 22 jam. Cells with stellate, vertical fusiform, and multipolar morphologies were labeled. Cells in the deep subdivision all had morphologies and sizes typical of projection neurons. To determine if labeled cells in the dense band were also projection neurons, WGA-HRP was injected into the lateral posterior nucleus and these sections were double-labeled with the glutamate antibody. Over one-half of cells in the dense band that were labeled by HRP were also obviously labeled by antibody. At the electron-microscope level, both medium-and large-sized neurons were also labeled by glutamate antibodies. These cells had different but characteristic morphologies.

Disinhibition in Rat Superior Colliculus Mediated by GABACReceptors

“…GABA accumulation or GABA-like immunoreactivity have been shown for horizontal, piriform, and stellate cells, and all of these populations of morphologically defined cell types are likely to include local GABAergic interneurons (Mize et al, 1982;Mize, 1988Mize, , 1992. However, cells with stellate morphology can also show glutamate-like immunoreactivity, and therefore this morphological class may also include nonGABAergic projection neurons (Jeon et al, 1997). Narrow-field cells and wide-field cells are not GABAergic and are regarded as projection neurons.…”

Long-Term Potentiation in the Juvenile Superior Colliculus Requires Simultaneous Activation of NMDA Receptors and L-type Ca2+Channels and Reflects Addition of Newly Functional Synapses

“…1 A) (Mooney et al, 1985;Jeon et al, 1997). These neurons express L-type Ca 2ϩ channels in the mouse sSC and probably correspond to the vertical fusiform neurons thought to be glutamate-containing relay cells in the cat's SC (Jeon et al, 1997).…”

“…The selected neurons lie in the intermediate and deeper SGS and have radially elongated or pyramidal cell bodies with several apical and basal dendrites directed, respectively, toward the pia and the deeper collicular layers. These cells have been termed narrow-field vertical neurons by previous investigators (Langer and Lund, 1974) and have been shown to be excited by visual stimulation in rodents (Mooney et al, 1985) and to be glutamatergic in cats (Jeon et al, 1997). Neuronal soma and proximal dendrites were visualized using a Nikon (Tokyo, Japan; E600FN) infrared differential interference contrast (DIC) microscope with a 60ϫ water-immersion objective and video camera (CCD-300T-RC; DAGE MTI, Michigan City, IN) and filled with biocytin (see below) in 15-20 experiments to verify the relationship between the DIC images and the full extent of the dendritic arbor.…”

“…To minimize variation in results attributable to neuron type, we focused recording on narrow-field vertical neurons (Langer and Lund, 1974) believed to be prominent excitatory neurons in the SGS ( Fig. 1 A) (Mooney et al, 1985;Jeon et al, 1997). These neurons express L-type Ca 2ϩ channels in the mouse sSC and probably correspond to the vertical fusiform neurons thought to be glutamate-containing relay cells in the cat's SC (Jeon et al, 1997).…”

Expressão dos receptores metabotrópicos de glutamato no sistema visual de ratos e pintos após enucleação ocular.

“…Além disso, consideramos o fato que há perda da maquinaria protéica, como fatores de transcrição, das aferências retinianas e perda do aporte protéico nos terminais neuronais em degeneração no colículo superior. Por exemplo, remoção unilateral de áreas corticais visuais leva a redução de glutamato na neurópila e pericários no CS de gatos, provavelmente interferindo em processos neuroquímicos das células do CS (Jeon et al, 1997a;Jeon et al, 1997b).…”