Gyrus Granule Cells (gyrus + granule_cell)

Distribution by Scientific Domains

Kinds of Gyrus Granule Cells

  • dentate gyrus granule cell

  • Selected Abstracts

    Role of the GLT-1 subtype of glutamate transporter in glutamate homeostasis: the GLT-1-preferring inhibitor WAY-855 produces marginal neurotoxicity in the rat hippocampus

    Julie V. Selkirk
    Abstract Glutamate is the major excitatory neurotransmitter in the central nervous system and is tightly regulated by cell surface transporters to avoid increases in concentration and associated neurotoxicity. Selective blockers of glutamate transporter subtypes are sparse and so knock-out animals and antisense techniques have been used to study their specific roles. Here we used WAY-855, a GLT-1-preferring blocker, to assess the role of GLT-1 in rat hippocampus. GLT-1 was the most abundant transporter in the hippocampus at the mRNA level. According to [3H]- l -glutamate uptake data, GLT-1 was responsible for approximately 80% of the GLAST-, GLT-1-, and EAAC1-mediated uptake that occurs within dissociated hippocampal tissue, yet when this transporter was preferentially blocked for 120 h with WAY-855 (100 m), no significant neurotoxicity was observed in hippocampal slices. This is in stark contrast to results obtained with TBOA, a broad-spectrum transport blocker, which, at concentrations that caused a similar inhibition of glutamate uptake (10 and 30 m), caused substantial neuronal death when exposed to the slices for 24 h or longer. Likewise, WAY-855, did not significantly exacerbate neurotoxicity associated with simulated ischemia, whereas TBOA did. Finally, intrahippocampal microinjection of WAY-855 (200 and 300 nmol) in vivo resulted in marginal damage compared with TBOA (20 and 200 nmol), which killed the majority of both CA1,4 pyramidal cells and dentate gyrus granule cells. These results indicate that selective inhibition of GLT-1 is insufficient to provoke glutamate build-up, leading to NMDA receptor-mediated neurotoxic effects, and suggest a prominent role of GLAST and/or EAAC1 in extracellular glutamate maintenance. [source]

    Rapid and long-term alterations of hippocampal GABAB receptors in a mouse model of temporal lobe epilepsy

    Andrea Straessle
    Abstract Alterations of ,-aminobutyric acid (GABA)B receptor expression have been reported in human temporal lobe epilepsy (TLE). Here, changes in regional and cellular expression of the GABAB receptor subunits R1 (GBR1) and R2 (GBR2) were investigated in a mouse model that replicates major functional and histopathological features of TLE. Adult mice received a single, unilateral injection of kainic acid (KA) into the dorsal hippocampus, and GABAB receptor immunoreactivity was analysed between 1 day and 3 months thereafter. In control mice, GBR1 and GBR2 were distributed uniformly across the dendritic layers of CA1,CA3 and dentate gyrus. In addition, some interneurons were labelled selectively for GBR1. At 1 day post-KA, staining for both GBR1 and GBR2 was profoundly reduced in CA1, CA3c and the hilus, and no interneurons were visible anymore. At later stages, the loss of GABAB receptors persisted in CA1 and CA3, whereas staining increased gradually in dentate gyrus granule cells, which become dispersed in this model. Most strikingly, a subpopulation of strongly labelled interneurons reappeared, mainly in the hilus and CA3 starting at 1 week post-KA. In double-staining experiments, these cells were selectively labelled for neuropeptide Y. The number of GBR1-positive interneurons also increased contralaterally in the hilus. The rapid KA-induced loss of GABAB receptors might contribute to epileptogenesis because of a reduction in both presynaptic control of transmitter release and postsynaptic inhibition. In turn, the long-term increase in GABAB receptors in granule cells and specific subtypes of interneurons may represent a compensatory response to recurrent seizures. [source]

    Statistical morphological analysis of hippocampal principal neurons indicates cell-specific repulsion of dendrites from their own cell

    Alexei V. Samsonovich
    Abstract Traditionally, the sources of guidance cues for dendritic outgrowth are mainly associated with external bodies (A) rather than with the same neuron from which dendrites originate (B). To quantify the relationship between factors A and B as determinants of the adult dendritic shape, the morphology of 83 intracellularly characterized, stained, completely reconstructed, and digitized principal neurons of the rat hippocampus was statistically analyzed using Bayesian optimization. It was found that the dominant directional preference (tropism) manifested in dendritic turns is to grow away from the soma rather than toward the incoming fibers or in any other fixed direction; therefore, B is predominant. Results are robust and consistent for all examined morphological classes (dentate gyrus granule cells, basal and apical trees of CA3 and CA1 pyramidal cells). In addition, computer remodeling of neurons based on the measured parameters produced virtual structures consistent with real morphologies, as confirmed by measurement of several global emergent parameters. Thus, the simple description of dendritic shape based on dendrites' tendency to grow straight, away from their own soma, and with additional random deflections, proves remarkably accurate and complete. Although based on adult neurons, these results suggest that dendritic guidance during development may be associated primarily with the host cell. This possibility challenges the traditional concept of dendritic guidance: in that hippocampal cells are densely packed and have highly overlapping dendritic fields, the somatodendritic repulsion must be cell specific. Plausible mechanisms involving extracellular effects of spikes are discussed, together with feasible experimental tests and predicted results. 2002 Wiley-Liss, Inc. [source]

    Exercise Neuroprotection in a Rat Model of Binge Alcohol Consumption

    ALCOHOLISM, Issue 3 2010
    J. Leigh Leasure
    Background:, Excessive alcohol intake produces structural and functional deficits in corticolimbic pathways that are thought to underlie cognitive deficits in the alcohol use disorders (AUDs). Animal models of binge alcohol administration support the direct link of high levels of alcohol consumption and neurotoxicity in the hippocampus and surrounding cortex. In contrast, voluntary wheel running enhances hippocampal neurogenesis and generally promotes the health of neurons. Methods:, We investigated whether voluntary exercise prior to binge alcohol exposure could protect against alcohol-induced cell loss. Female Long-Evans rats exercised voluntarily for 14 days before undergoing 4 days of binge alcohol consumption. Brains were harvested immediately after the last dose of alcohol and examined for various histological markers of neurodegeneration, including both cell death (FluoroJade B) and cell birth (Ki67) markers. Results:, Rats that exercised prior to binge exposure were significantly less behaviorally intoxicated, which was not a result of enhanced hepatic metabolism. Rats that exercised prior to binge alcohol consumption had reduced loss of dentate gyrus granule cells and fewer FluoroJade B positive cells in the dentate gyrus and associated entorhinal-perirhinal cortex compared to nonexercisers. However, exercise did not protect against cell death in the piriform cortex nor protect against alcohol-induced decreases in cell proliferation, evidenced by a similar alcohol-induced reduction in Ki67 labeled cells between exercise and sedentary rats. Conclusions:, We conclude that exercise can reduce behavioral sensitivity to ethanol intoxication and protect vulnerable brain areas from alcohol-induced cell death. Exercise neuroprotection of alcohol-induced brain damage has important implications in understanding the neurobiology of the AUDs as well as in developing novel treatment strategies. [source]

    Distribution of the protein IMPACT, an inhibitor of GCN2, in the mouse, rat, and marmoset brain

    Simone Bittencourt
    Abstract IMPACT is an inhibitor of GCN2, a kinase that phosphorylates the alpha subunit of the translation initiation factor 2 (eIF2,). GCN2 has been implicated in regulating feeding behavior and learning and memory in mice. IMPACT is highly abundant in the brain, suggesting its relevance in the control of GCN2 activation in the central nervous system. We describe here the distribution of IMPACT in the brain of rodents (mice and rats) and of a primate (marmoset) using highly specific antibodies raised against the mouse IMPACT protein. Neurons expressing high levels of IMPACT were found in most areas of the brain. In the hippocampal formation the lack of IMPACT in the dentate gyrus granule cells was striking. The hypothalamus is exceptionally rich in neurons expressing high levels of IMPACT, particularly in the suprachiasmatic nucleus. The only exception to this pattern was the ventromedial nucleus. The thalamic neurons are mostly devoid of IMPACT, with the exception of the paraventricular, reuniens and reticular nuclei, and intergeniculate leaf. The brainstem displayed high levels of IMPACT. For the marmoset, IMPACT expression in the brain is not as prominent when compared to other organs. In the marmoset brain the pattern of IMPACT expression was similar to rodents in most areas, except for the very strong labeling of the Purkinje cells, the lack of IMPACT-positive neurons in the nucleus reuniens, and weak labeling of interneurons in the hippocampus. GCN1, the activator of GCN2 to which IMPACT binds, is widely distributed in all neuronal populations, and all IMPACT-positive cells were also GCN1-positive. The data presented herein suggest that IMPACT may be involved in biochemical homeostatic mechanisms that would prevent GCN2 activation and therefore ATF4 (CREB-2) synthesis in neurons. J. Comp. Neurol. 507:1811,1830, 2008. 2008 Wiley-Liss, Inc. [source]

    Action potential initiation and propagation in hippocampal mossy fibre axons

    Christoph Schmidt-Hieber
    Dentate gyrus granule cells transmit action potentials (APs) along their unmyelinated mossy fibre axons to the CA3 region. Although the initiation and propagation of APs are fundamental steps during neural computation, little is known about the site of AP initiation and the speed of propagation in mossy fibre axons. To address these questions, we performed simultaneous somatic and axonal whole-cell recordings from granule cells in acute hippocampal slices of adult mice at ,23C. Injection of short current pulses or synaptic stimulation evoked axonal and somatic APs with similar amplitudes. By contrast, the time course was significantly different, as axonal APs had a higher maximal rate of rise (464 30 V s,1 in the axon versus 297 12 V s,1 in the soma, mean s.e.m.). Furthermore, analysis of latencies between the axonal and somatic signals showed that APs were initiated in the proximal axon at ,20,30 ,m distance from the soma, and propagated orthodromically with a velocity of 0.24 m s,1. Qualitatively similar results were obtained at a recording temperature of ,34C. Modelling of AP propagation in detailed cable models of granule cells suggested that a ,4 times higher Na+ channel density (,1000 pS ,m,2) in the axon might account for both the higher rate of rise of axonal APs and the robust AP initiation in the proximal mossy fibre axon. This may be of critical importance to separate dendritic integration of thousands of synaptic inputs from the generation and transmission of a common AP output. [source]