Morphology and glutamate receptor characterization of identified entorhinal and hippocampal projection neurons in the primate.
Item
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Title
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Morphology and glutamate receptor characterization of identified entorhinal and hippocampal projection neurons in the primate.
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Identifier
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AAI9417466
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identifier
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9417466
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Creator
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Good, Paul Francis.
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Contributor
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Adviser: John H. Morrison
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Neuroscience | Biology, Anatomy
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Abstract
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The entorhinal cortex is a critical link between widespread areas of neocortex and the hippocampus. Neocortical afferents to entorhinal cortex are well characterized and provide highly processed information to the entorhinal cortex. Reciprocal efferent connections from ERC back to neocortex are less well characterized. Projections that provide outflow from the hippocampal formation to neocortex are thought to represent a crucial set of circuits underlying declarative memory.;In the present study, such a projection from entorhinal cortex to the polymodal region of superior temporal sulcus, TPO, has been characterized by morphological and neurochemical criteria. Using retrograde tracing combined with cell filling and dual label immunocytochemistry, the dendritic arbor and kainate class glutamate receptor subunit content of identified entorhinal projection neurons has been determined. Finally, the distribution of kainate receptors at the ultrastructural level in the entorhinal cortex and at the light and electron microscopic level in the hippocampus was analysed.;Results show that identified entorhinal projection neurons consist of multiple morphological types, with dendritic arbors largely confined to layer V of the entorhinal cortex. Kainate class glutamate receptor subunit immunoreactivity was distributed extensively throughout the lamina of the entorhinal cortex, particularly in layers II and V/VI. Analysis of GluR5/6/7 immunoreactivity in the dendritic arbor of identified entorhinal projection neurons showed that the complete extent of such neurons was kainate receptor immunoreactive. A dendritic arbor confined to layer V indicates that such identified entorhinal projection neurons complete a loop of information processing through the hippocampus, returning to neocortex.;In the hippocampal formation, kainate class glutamate receptors were present in all subfields. Kainate receptor immunoreactivity at the ultrastructural level was present in asymmetric postsynaptic densities in about half of all asymmetric synapses counted. In CA1 stratum radiatum and CA3 stratum lucidum, virtually all GluR5/6/7-ir synapses were axospinous and GluR5/6/7-ir synapses in the molecular lamina of the hippocampus varied from fields with a majority on spines: dentate gyrus (64%) and CA1 (71%); to CA3 (24%) with a minority on spines. Entorhinal layers II and V also demonstrated a minority of immunolabeled PSDs on spines in the material analysed. The widespread presence of kainate receptors in the hippocampal formation indicates that such receptors play a prominent role in hippocampal neurotransmission and may also play a role in synaptic plasticity and neurodegenerative disease.
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Type
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dissertation
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Source
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PQT Legacy Restricted.xlsx
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degree
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Ph.D.