Synapse Plasticity in Motor, Sensory, and Limbo-Prefrontal Cortex Areas as Measured by Degrading Axon Terminals in an Environment Model of Gerbils (Meriones unguiculatus)

Abstract

Still little is known about naturally occurring synaptogenesis in the adult neocortex and related impacts of epigenetic influences. We therefore investigated (pre)synaptic plasticity in various cortices of adult rodents, visualized by secondary lysosome accumulations (LA) in remodeling axon terminals. Twenty-two male gerbils from either enriched (ER) or impoverished rearing (IR) were used for quantification of silver-stained LA. ER-animals showed rather low LA densities in most primary fields, whereas barrel and secondary/associative cortices exhibited higher densities and layer-specific differences. In IR-animals, these differences were evened out or even inverted. Basic plastic capacities might be linked with remodeling of local intrinsic circuits in the context of cortical map adaptation in both IR- and ER-animals. Frequently described disturbances due to IR in multiple corticocortical and extracortical afferent systems, including the mesocortical dopamine projection, might have led to maladaptations in the plastic capacities of prefronto-limbic areas, as indicated by different LA densities in IR- compared with ER-animals.

Synaptic Remodeling in the Dentate Gyrus, CA3, CA1, Subiculum, and Entorhinal Cortex of Mice: Effects of Deprived Rearing and Voluntary Running

“…It seems, in fact, that in CD1 mice CA3 and CA1 also exhibit intrinsic plasticity. This assumption finds support in recent findings of a systematic analysis of synaptic turnover rates in diverse cortical areas of the gerbil, showing that associative cortical areas also display synaptic remodeling, and region—as well as layer-specific differences which appear mainly determined by local and distant associative connections [7]. These layer-specific differences were leveled after environmental deprivation during rearing, an effect that parallels our findings after wheel running in CD1 mice.…”

Structural covariance networks of striatum subdivision in patients with Parkinson's disease

“…In addition, dopamine receptor activation has been proved to mobilize the striatal neuronal cytoskeleton and modulate GABA neuron migration in the basal forebrain, supporting the result of an increased mesotelencephalic intranetwork r Chou et al r r 1580 r connection [Crandall et al, 2007]. Finally, concomitant higher ability to display synaptic rewiring and changes in the dendritic arborization in the limbic system than in neocortex, eventually increasing interregional morphometric correlations in caudate-limbic network [Butz et al, 2009;Neufeld et al, 2009]. We believe dopamine depletion in PD may, therefore, force neuron remodeling and structural plasticity in both its modulated region and their downstream areas [Braak et al, 2000].…”

Structural covariance of the neostriatum with regional gray matter volumes

“…There are also regional differences in the capacity to show structural plasticity. It has been reported that structural plasticity (i.e., synaptic turnover or rewiring, and changes in the dendritic arborization or spine density) is much more frequently observed in limbic regions than in the prefrontal, motor and sensory cortices (Butz et al, 2009;Kolb et al 2003;Neufeld et al 2009).…”

“…Significantly, such regional differences in the capacity to show structural plasticity seem to be mediated by the presence of particular neurotransmitters, which may act as neurotrophic factors. Structural plasticity in prefrontal and limbic cortices depends on optimal dopamine levels (Neufeld et al 2009), and, in humans, structural covariance between the neostriatum and the dorsolateral prefrontal cortex is increased in the carriers of a specific haplotype of a protein (DARPP-32) related to molecular mechanisms of dopaminergic neurotransmission (Meyer-Lindenberg 2009).…”