Neuroscience
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Comparative Study
Differential effects of prenatal stress on the morphological maturation of hippocampal neurons.
The present study was designed to clarify an intensity-dependent effect of prenatal stress on the morphological development of hippocampal neurons in rats. In addition, the involvement of receptors for glucocorticoids, i.e. mineralocorticoid receptors and glucocorticoid receptors, in stress-induced changes in the morphology of hippocampal neurons was examined by an in vitro pharmacological approach. The effects of mild prenatal stress on neurogenesis and long-term potentiation in the hippocampus were also investigated in adult offspring. ⋯ In contrast, glucocorticoid receptor was involved in the suppression of their morphology. Short-lasting, mild prenatal stress, which has previously been shown to enhance learning performance in adult offspring, facilitated neurogenesis and long-term potentiation in the adult hippocampus. These findings suggest that prenatal stress has enhancing and suppressing effects on the development of hippocampal neurons depending on intensity, and that mineralocorticoid receptors and glucocorticoid receptors contribute to stress-induced morphological changes.
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Comparative Study
Gene expression in the rat cerebral cortex: comparison of recovery sleep and hypnotic-induced sleep.
Most hypnotic medications currently on the market target some aspect of GABAergic neurotransmission. Although all such compounds increase sleep, these drugs differentially affect the activity of the cerebral cortex as measured by the electroencephalogram. Whereas benzodiazepine medications such as triazolam tend to suppress slow wave activity in the cortex, the GABA(B) ligand gamma-hydroxybutyrate greatly enhances slow wave activity and the non-benzodiazepine, zolpidem, which binds to the omega1 site on the GABA(A) receptor/Cl(-) ionophore complex, is intermediate in this regard. ⋯ We find that, although each drug increases the expression of a subset of genes in the panel of biomarkers, no drug fully replicates the molecular changes in the cortex associated with recovery sleep. Furthermore, high levels of slow wave activity in the cortex are correlated with increased expression of fra-2 whereas the expression of grp94 is correlated with body temperature. These results demonstrate that sleep-related changes in gene expression may be affected by physiological covariates of sleep and wakefulness rather than by vigilance state per se.
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Comparative Study
Stereological estimation of Purkinje neuron number in C57BL/6 mice and its relation to associative learning.
Cerebellar Purkinje neurons are among the most vulnerable neurons in the CNS. Impairment in Purkinje neurons has consequences for cerebellar cortical-dependent forms of behavior. The primary aim of this study was to evaluate Purkinje neuron number over the lifespan of C57BL/6 mice. ⋯ Eliminating the hearing-impaired 18- and 24-month-old mice from the analysis, the correlation between Purkinje neuron number and rate of conditioning was -0.435 (P=0.053) in 15 younger mice aged 4-12 months. Purkinje neurons are one of the few types of neurons showing significant age-associated loss. Results indicate that individual variation in Purkinje neuron number is related to eyeblink conditioning in young organisms suggesting that reserves of neuron numbers against which individuals draw are defined early in life.
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Comparative Study
The dynamic range and domain-specific signals of intracellular calcium in photoreceptors.
Vertebrate photoreceptors consist of strictly delimited subcellular domains: the outer segment, ellipsoid, cell body and synaptic terminal, each hosting crucial cellular functions, including phototransduction, oxidative metabolism, gene expression and transmitter release. We used optical imaging to explore the spatiotemporal dynamics of Ca(2+) signaling in non-outer segment regions of rods and cones. Sustained depolarization, designed to emulate photoreceptor activation in the darkness, evoked a standing Ca(2+) gradient in tiger salamander photoreceptors with spatially-averaged intracellular Ca(2+) concentration within synaptic terminals of approximately 2 microM and lower (approximately 750 nM) intracellular calcium concentration in the ellipsoid. ⋯ L-type voltage-operated Ca(2+) channels and plasma membrane Ca(2+) ATPases were highly expressed in synaptic terminals with progressively lower expression levels in the cell body and ellipsoid. These results show photoreceptor Ca(2+) homeostasis is controlled in a region-specific manner by direct Ca(2+) entry and diffusion as well as Ca(2+) extrusion. Moreover, quantitative measurement of intracellular calcium concentration levels in different photoreceptor compartments indicates that the dynamic range of Ca(2+) signaling in photoreceptors is approximately 40-fold, from approximately 50 nM in the light to approximately 2 microM in darkness.
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Comparative Study
Atp2b2, encoding plasma membrane Ca2+-ATPase type 2, (PMCA2) exhibits tissue-specific first exon usage in hair cells, neurons, and mammary glands of mice.
Atp2b2 encodes the plasma membrane Ca(2+)-ATPase type 2 (PMCA2) expressed in various tissues, including stereocilia of cochlear and vestibular hair cells, cerebellar Purkinje cells, and lactating mammary epithelia. Mutations of the gene lead to deafness, ataxia, and reduced Ca(2+) levels in milk. Heterozygous mutants also have abnormal hearing, suggesting that precise regulation of Atp2b2 is required for normal function. ⋯ The regions around the mu and delta first exons are highly conserved between rat and mouse, but less so with other species. Our results show that expression of Atp2b2 is highly regulated, using four different transcriptional start regions, two of which are differentially expressed in neuronal tissue. This suggests that unique regulatory mechanisms are used to control Atp2b2 expression in different types of cells.