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Life Sciences87%

Selected Abstracts

Conservation and expression of IQ-domain-containing calpacitin gene products (neuromodulin/GAP-43, neurogranin/RC3) in the adult and developing oscine song control system

DEVELOPMENTAL NEUROBIOLOGY, Issue 2-3 2009
David F. Clayton
Abstract Songbirds are appreciated for the insights they provide into regulated neural plasticity. Here, we describe the comparative analysis and brain expression of two gene sequences encoding probable regulators of synaptic plasticity in songbirds: neuromodulin (GAP-43) and neurogranin (RC3). Both are members of the calpacitin family and share a distinctive conserved core domain that mediates interactions between calcium, calmodulin, and protein kinase C signaling pathways. Comparative sequence analysis is consistent with known phylogenetic relationships, with songbirds most closely related to chicken and progressively more distant from mammals and fish. The C-terminus of neurogranin is different in birds and mammals, and antibodies to the protein reveal high expression in adult zebra finches in cerebellar Purkinje cells, which has not been observed in other species. RNAs for both proteins are generally abundant in the telencephalon yet markedly reduced in certain nuclei of the song control system in adult canaries and zebra finches: neuromodulin RNA is very low in RA and HVC (relative to the surrounding pallial areas), whereas neurogranin RNA is conspicuously low in Area X (relative to surrounding striatum). In both cases, this selective downregulation develops in the zebra finch during the juvenile song learning period, 25,45 days after hatching. These results suggest molecular parallels to the robust stability of the adult avian song control circuit. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source]

Increasing stereotypy in adult zebra finch song correlates with a declining rate of adult neurogenesis

DEVELOPMENTAL NEUROBIOLOGY, Issue 13 2007
Carolyn L. Pytte
Abstract Adult neurogenesis is often correlated with learning new tasks, suggesting that a function of incorporating new neurons is to permit new memory formation. However, in the zebra finch, neurons are added to the song motor pathway throughout life, long after the initial song motor pattern is acquired by about 3 months of age. To explore this paradox, we examined the relationship between adult song structure and neuron addition using sensitive measures of song acoustic structure. We report that between 4 and 15 months of age there was an increase in the stereotypy of fine-grained spectral and temporal features of syllable acoustic structure. These results indicate that the zebra finch continues to refine motor output, perhaps by practice, over a protracted period beyond the time when song is first learned. Over the same age range, there was a decrease in the addition of new neurons to HVC, a region necessary for song production, but not to Area X or the hippocampus, regions not essential for singing. We propose that age-related changes in the stereotypy of syllable acoustic structure and HVC neuron addition are functionally related. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source]

Subcellular compartmentalization of aromatase is sexually dimorphic in the adult zebra finch brain

DEVELOPMENTAL NEUROBIOLOGY, Issue 1 2007
Kevin N. Rohmann
Abstract The vertebrate brain is a source of estrogen (E) via the expression of aromatase (E-synthase). In the zebra finch (Taeniopygia guttata), despite documented dimorphisms in E-action, no differences are detectable in circulating E, or the neural levels of aromatase transcription, activity, or somal protein expression. Studies of aromatase expression at the light- and electron-microscope levels reveal greater numbers of fibers and presynaptic boutons in adult males relative to females. We assayed aromatase activity and content in synaptosomes and microsomes from the anterior [containing lMAN and Area X (males)] and posterior telencephalon (containing HVC and RA) of adult birds. In contrast to non-song birds and mammals, both cell fractions contain abundant aromatase measurable in terms of activity (enzyme assays) and content (Western blots) with minimal enrichment in microsomes. From brain homogenates of identical concentration, aromatase activity was higher in the synaptosomal relative to the microsomal fraction, in males relative to females, and in the posterior compared to anterior telencephalon. These effects were driven by high levels of synaptosomal aromatase in the male posterior telencephalon. These data suggest that males possess more aromatase per presynaptic bouton, or a greater number of aromatase-containing presynaptic boutons than females in the posterior telencephalon. Further, the present report reveals synaptic aromatization as a considerable source of E in the zebra finch brain, and supports the idea that telencephalic synapses in and around the adult male song production nuclei may be exposed to higher levels of E compared to the female brain. © 2006 Wiley Periodicals, Inc. J Neurobiol 67: 1,9, 2007 [source]

Dopamine receptors in a songbird brain

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 6 2010
Lubica Kubikova
Abstract Dopamine is a key neuromodulatory transmitter in the brain. It acts through dopamine receptors to affect changes in neural activity, gene expression, and behavior. In songbirds, dopamine is released into the striatal song nucleus Area X, and the levels depend on social contexts of undirected and directed singing. This differential release is associated with differential expression of activity-dependent genes, such as egr1 (avian zenk), which in mammalian brain are modulated by dopamine receptors. Here we cloned from zebra finch brain cDNAs of all avian dopamine receptors: the D1 (D1A, D1B, D1D) and D2 (D2, D3, D4) families. Comparative sequence analyses of predicted proteins revealed expected phylogenetic relationships, in which the D1 family exists as single exon and the D2 family exists as spliced exon genes. In both zebra finch and chicken, the D1A, D1B, and D2 receptors were highly expressed in the striatum, the D1D and D3 throughout the pallium and within the mesopallium, respectively, and the D4 mainly in the cerebellum. Furthermore, within the zebra finch, all receptors, except for D4, showed differential expression in song nuclei relative to the surrounding regions and developmentally regulated expression that decreased for most receptors during the sensory acquisition and sensorimotor phases of song learning. Within Area X, half of the cells expressed both D1A and D2 receptors, and a higher proportion of the D1A-only-containing neurons expressed egr1 during undirected but not during directed singing. Our findings are consistent with hypotheses that dopamine receptors may be involved in song development and social context-dependent behaviors. J. Comp. Neurol. 518:741,769, 2010. © 2009 Wiley-Liss, Inc. [source]

IR-SE and IR-MEMRI allow in vivo visualization of oscine neuroarchitecture including the main forebrain regions of the song control system

NMR IN BIOMEDICINE, Issue 1 2006
Ilse Tindemans
Abstract Songbirds share with humans the capacity to produce learned vocalizations (song). Recently, two major regions within the songbird's neural substrate for song learning and production; nucleus robustus arcopallii (RA) and area X (X) are visualized in vivo using Manganese Enhanced MRI (MEMRI). The aim of this study is to extend this to all main interconnected forebrain Song Control Nuclei. The ipsilateral feedback circuits allow Mn2+ to reach all main Song Control Nuclei after stereotaxic injection of very small doses of MnCl2 (10,nl of 10,mM) into HVC of one and MAN (nucleus magnocellularis nidopallii anterioris) of the other hemisphere. Application of a high resolution (80,µ) Spin Echo Inversion Recovery sequence instead of conventional T1-weighted Spin Echo images improves the image contrast dramatically such that some Song Control Nuclei, ventricles, several laminae, fibre tracts and other specific brain regions can be discerned. The combination of this contrast-rich IR-SE sequence with the transsynaptic transport property of Manganese (Inversion Recovery based MEMRI (IR-MEMRI)) enables the visualization of all main interconnected components of the Song Control System in telencephalon and thalamus. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Dopamine Receptors in a Songbird Brain

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 6 2010
Lubica Kubikova
Dopamine is a key neuromodulatory transmitter in the brain. It acts through dopamine receptors to affect changes in neural activity, gene expression, and behavior. In songbirds, dopamine is released into the striatal song nucleus area X, and the levels depend on social contexts of undirected and directed singing. This differential release is associated with differential expression of activity-dependent genes, such as egr1 (avian zenk), which in mammalian brain are modulated by dopamine receptors. Here we cloned from zebra finch brain cDNAs of all avian dopamine receptors: the D1 (D1A, D1B, D1D) and D2 (D2, D3, D4) families. Comparative sequence analyses of predicted proteins revealed expected phylogenetic relationships, in which the D1 family exists as single exon and the D2 family exists as spliced exon genes. In both zebra finch and chicken, the D1A, D1B, and D2 receptors were highly expressed in the striatum, the D1D and D3 throughout the pallium and within the mesopallium, respectively, and the D4 mainly in the cerebellum. Furthermore, within the zebra finch, all receptors, except for D4, showed differential expression in song nuclei relative to the surrounding regions and developmentally regulated expression that decreased for most receptors during the sensory acquisition and sensorimotor phases of song learning. Within area X, half of the cells expressed both D1A and D2 receptors, and a higher proportion of the D1A-only-containing neurons expressed egr1 during undirected but not during directed singing. Our findings are consistent with hypotheses that dopamine receptors may be involved in song development and social context-dependent behaviors. J. Comp. Neurol. 518:741,769, 2010. © 2009 Wiley-Liss, Inc. [source]