The NMDAR1 subunit of the N-methyl-D-aspartate receptor is localized at postsynaptic sites opposite both retinal and cortical terminals in the cat superior colliculus

2000 ◽  
Vol 17 (1) ◽  
pp. 41-53 ◽  
Author(s):  
R. RANNEY MIZE ◽  
GRACE D. BUTLER
Keyword(s):  
Superior Colliculus ◽  
Receptor Protein ◽  
Sensory Afferents ◽  
Light Microscope Level ◽  
Synaptic Localization ◽  
Synaptic Terminals ◽  
Cortical Afferents ◽  
Aspartate Receptor ◽  
Presynaptic Dendrites ◽  
Antibody Labeling

The N-methyl-D-aspartate receptor (NMDAR) is an ionotropic glutamate receptor that is important in neurotransmission as well as in processes of synaptic plasticity in the mammalian superior colliculus (SC). Despite the importance of this receptor in synaptic transmission, there is as yet no evidence that demonstrates directly the synaptic localization of the NMDAR receptor in SC. We have used electron-microscope (EM) immunocytochemistry to localize the NMDAR1 subunit of this receptor protein and its association with sensory afferents in the cat SC. Retinal synaptic terminals were identified by normal morphology and cortical synaptic terminals by degeneration after lesions of areas 17–18 of the visual cortex. At the light-microscope level, label was densest within the superficial gray and upper optic layers, but also present in all other layers. Label was contained within cell bodies, dendrites, and a few putative axons. At the EM level, antibody labeling was found along postsynaptic densifications and internalized within the cytoplasm of a variety of dendrites and some cell bodies. Postsynaptic profiles labeled by NMDAR1 included conventional dendrites and presynaptic dendrites which contained pleomorphic synaptic vesicles and are known to be GABAergic. Many of the labeled postsynaptic densifications of both of these profile types received synaptic inputs from retinal or cortical terminals. Virtually no NMDAR1 immunoreactivity was found on thin dendritic thorns or putative spines, even when these were postsynaptic to retinal or cortical terminals. In summary, these results show that the NMDAR1 subunit is postsynaptic to both retinal and cortical afferents, which are known to be glutamatergic, and are consistent with physiological evidence showing that stimulation of either pathway can activate the NMDA receptor.

Glutamate containing neurons in the cat superior colliculus revealed by immunocytochemistry

1997 ◽  
Vol 14 (2) ◽  
pp. 387-393 ◽  
Author(s):  
Chang-Jin Jeon ◽  
Michael R. Gurski ◽  
R. Ranney Mize
Keyword(s):  
Electron Microscope ◽  
Superior Colliculus ◽  
Projection Neurons ◽  
Electron Microscope Level ◽  
Cortical Afferents ◽  
Lateral Posterior ◽  
Laminar Pattern ◽  
Lateral Posterior Nucleus ◽  
Dense Band ◽  
Cat Superior Colliculus

AbstractGlutamate 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 μm, with a mean of 22 μm. 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.

GABAC Receptors in the Rat Superior Colliculus and Pretectum Participate in Synaptic Neurotransmission

2003 ◽  
Vol 89 (4) ◽  
pp. 2035-2045 ◽  
Author(s):  
Mathias Boller ◽  
Matthias Schmidt
Keyword(s):  
Superior Colliculus ◽  
Receptor Antagonist ◽  
Kynurenic Acid ◽  
Receptor Type ◽  
Direct Function ◽  
Synaptic Localization ◽  
Postsynaptic Currents ◽  
Whole Cell Patch Clamp ◽  
Synaptic Neurotransmission

In mammals, GABAC receptors seem to be specifically expressed in the retina and the subcortical visual system, with highest extraretinal expression levels in the superior colliculus (SC). Although its presence in the superficial SC has been demonstrated physiologically, a direct involvement of this receptor type in fast synaptic neurotransmission still awaits verification. We addressed the question of a possible synaptic localization of GABACreceptors by performing in vitro whole-cell patch-clamp recordings of inhibitory postsynaptic currents (IPSCs) in single neurons of the rat SC and the neighboring pretectal nuclear complex, where GABAC receptors are also expressed at significant levels. To increase the likelihood to record IPSCs we induced spontaneous activity by application of the potassium channel blocker 4-aminopyridine (4-AP) and blocked glutamate-mediated excitatory neurotransmission with kynurenic acid. All 4-AP–induced postsynaptic currents were of synaptic origin because they were completely suppressed by lidocaine or by substitution of extracellular calcium with cobalt. In 40% of the SC cells and in 60% of the pretectal neurons, IPSCs in the presence of 4-AP and kynurenic acid were only partly blocked by the selective GABAA receptor antagonist bicuculline. Inhibitory currents that were insensitive to bicuculline, however, could be blocked by coapplication of either the specific GABAC receptor antagonist 1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid or picrotoxin, an unselective GABAA and GABACreceptor antagonist. We conclude that GABAC receptors are, at least partially, located synaptically in SC and pretectal neurons in the rat, which indicates a direct function of this receptor type for synaptic processing in both structures.

The superior colliculus of the ferret: Cortical afferents and efferent connections to dorsal thalamus

2010 ◽  
Vol 1353 ◽  
pp. 74-85 ◽  
Author(s):  
Paul R. Manger ◽  
C. Ernesto Restrepo ◽  
Giorgio M. Innocenti
Keyword(s):  
Superior Colliculus ◽  
Dorsal Thalamus ◽  
Efferent Connections ◽  
Cortical Afferents

Visual deprivation fails to reduce calbindin 28kD or GABA immunoreactivity in the Rhesus monkey superior colliculus

1992 ◽  
Vol 9 (2) ◽  
pp. 157-168 ◽  
Author(s):  
R. Ranney Mize ◽  
Qian Luo
Keyword(s):  
Superior Colliculus ◽  
Optical Density ◽  
Calcium Binding ◽  
Contact Lenses ◽  
Monocular Deprivation ◽  
Gamma Aminobutyric Acid ◽  
Full Field ◽  
Retinal Axons ◽  
Binocular Deprivation ◽  
Antibody Labeling

AbstractAntibody labeling of the calcium-binding protein calbindin 28kD (CaBP) and gamma-aminobutyric acid (GABA) is altered by short-term monocular deprivation in the lateral geniculate nucleus and visual cortex of adult primates. It is not known whether these alterations occur in other subcortical visual structures. We therefore have examined antibody labeling to CaBP and GABA in the superior colliculus (SC) of visually deprived Rhesus monkeys. One group was monocularly enucleated as adults. The other monkeys experienced different types of monocular and binocular deprivation from birth, including occlusion of one eye, and/or surgically induced aphakia, optically corrected with extended-wear contact lenses, or an intraocular lens implant. Some of these monkeys also had one eye enucleated prior to perfusion.In the SC of normal monkeys, CaBP-immunoreactive neurons formed three laminar tiers within SC, one within the zonal layer (ZL) and upper superficial gray layer (SGL), another bridging the optic and intermediate gray layers, and a third within the deep gray layer. CaBP neurons within the upper tier had small pyriform or stellate morphologies while those in the deeper tiers were slightly larger neurons, most with a stellate morphology. GABA-immunoreactive neurons were densely distributed within the SGL and more sparsely distributed within the deeper layers. These cells were mostly small neurons with horizontal, pyriform, or stellate morphologies.Neither monocular enucleation nor occlusion nor aphakia combined with continuous occlusion of the fellow eye produced any visible reduction in antibody labeling in cells or neuropil within the SC. Full-field measures of labeling intensity (optical density) within the ZL and upper SGL revealed no consistent differences between the SC contralateral or ipsilateral to the affected eye in either CaBP- or GABA-labeled sections. Measures of the optical density, number, and size of labeled neurons also showed no consistent effects of enucleation and/or occlusion. We therefore conclude that the retino-geniculostriate and retino-collicular systems differ in their response to deprivation which is likely due to the significant overlap of retinal axons from the two eyes that occurs in the SC of the Rhesus monkey.

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