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Title:Experience, neuroanatomical plasticity and expression of the immediate early gene ZENK in the visual cortex of weanling rats
Author(s):Wallace, Christopher Smith
Doctoral Committee Chair(s):Greenough, William T.
Department / Program:Biology, Neuroscience
Discipline:Biology, Neuroscience
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Neuroscience
Abstract:This investigation combines anatomical and molecular approaches to determine if expression of a specific regulatory transcription factor correlates with morphological plasticity, using a model of experience-dependent plasticity.
An initial study (Chapter 2) demonstrated that exposing weanling rats to a complex environment (EC) rapidly altered dendritic fields of neurons in visual cortex relative to littermates housed in individual cages (IC). This paradigm was employed to assess the behavioral induction of ZENK, a transcription factor implicated in plasticity by its association with hippocampal long-term potentiation.
Messenger RNA levels were quantified by in situ hybridization to determine if ZENK is: (1) behaviorally regulated (2) elevated in the visual cortex of rats actively exploring a complex environment (EC). To assess behavioral regulation, three groups were compared: EC; individually caged, but handled (HIC); and unhandled individually caged (IC) rats after short-term differential housing. Within the area of visual cortex where dendritic changes occur after short-term EC (Oc2), the three groups displayed significantly different levels of ZENK expression; EC $>$ HIC $>$ IC. In contrast, in a cortical region within which dendritic plasticity is undetectable (Fr2), no differences were observed in ZENK expression. Superficial cortical layers in Oc2, somatosensory and Fr1 were all significantly elevated in EC relative to controls, suggesting sensory afferent projections to cortex are an important component. Induction of ZENK in the striatum of EC rats suggests that plasticity of this structure may be part of the brain's response to environmental complexity.
The anatomical distribution of ZENK mRNA was similar in all behavioral groups. A modular pattern of ZENK labeling in the cortex of all groups was observed and may implicate ZENK in cortical integration.
ZENK elevation in EC visual cortex was observed at 4, 15 and 30 days of exposure. Hence, the process(es) ZENK mediates continue throughout the 30 day period. The time course of ZENK induction or the efficiency of translation could vary, however, in response to behavioral stimulation at these different ages.
These results indicate that the transcription factor ZENK is sensitive to behavioral stimulation and may regulate the cellular support of, or preparation for, plasticity.
Issue Date:1994
Rights Information:Copyright 1994 Wallace, Christopher Smith
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9416447
OCLC Identifier:(UMI)AAI9416447

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