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At least 1,135 records · Page 63Linked to original sources
PubMed2004

Vesicular inhibitory amino acid transporter is expressed in gamma-aminobutyric acid (GABA)-containing astrocytes in rat pineal glands.

Gamma-aminobutyric acid (GABA) is an inhibitory amino acid and acts as an intercellular transmitter in the central nervous system and peripheral tissues. In pineal glands, GABA is supposed to be a paracrine-like modulator of secretion of melatonin, although its mode of action, especially the sites of GABA signal appearance, is unknown. Vesicular inhibitory amino acid transporter (VIAAT) is a potential marker for the GABAergic phenotype. Here we presented evidence that VIAAT is expressed in GFAP-expressing astrocytes and a subpopulation of OX42-expressing microglia, but not in pinealocytes in cultured cells of rat pineal glands. The VIAAT-expressing cells also exhibit GABA immunoreactivity. Essentially the same results were obtained for pineal glands. These results suggest that GABA is stored and secreted from astrocytes and a subpopulation of microglia in pineal glands.

Amino Acid Transport Systems↗
PubMed2004

Multiple roles for the active zone protein RIM1alpha in late stages of neurotransmitter release.

The active zone protein RIM1alpha interacts with multiple active zone and synaptic vesicle proteins and is implicated in short- and long-term synaptic plasticity, but it is unclear how RIM1alpha's biochemical interactions translate into physiological functions. To address this question, we analyzed synaptic transmission in autaptic neurons cultured from RIM1alpha-/- mice. Deletion of RIM1alpha causes a large reduction in the readily releasable pool of vesicles, alters short-term plasticity, and changes the properties of evoked asynchronous release. Lack of RIM1alpha, however, had no effect on synapse formation, spontaneous release, overall Ca2+ sensitivity of release, or synaptic vesicle recycling. These results suggest that RIM1alpha modulates sequential steps in synaptic vesicle exocytosis through serial protein-protein interactions and that this modulation is the basis for RIM1alpha's role in synaptic plasticity.

Adenosine↗
PubMed2005

A splice code for trans-synaptic cell adhesion mediated by binding of neuroligin 1 to alpha- and beta-neurexins.

Previous studies suggested that postsynaptic neuroligins form a trans-synaptic complex with presynaptic beta-neurexins, but not with presynaptic alpha-neurexins. Unexpectedly, we now find that neuroligins also bind alpha-neurexins and that alpha- and beta-neurexin binding by neuroligin 1 is regulated by alternative splicing of neuroligin 1 (at splice site B) and of neurexins (at splice site 4). In neuroligin 1, splice site B is a master switch that determines alpha-neurexin binding but leaves beta-neurexin binding largely unaffected, whereas alternative splicing of neurexins modulates neuroligin binding. Moreover, neuroligin 1 splice variants with distinct neurexin binding properties differentially regulate synaptogenesis: neuroligin 1 that binds only beta-neurexins potently stimulates synapse formation, whereas neuroligin 1 that binds to both alpha- and beta-neurexins more effectively promotes synapse expansion. These findings suggest that neuroligin binding to alpha- and beta-neurexins mediates trans-synaptic cell adhesion but has distinct effects on synapse formation, indicating that expression of different neuroligin and neurexin isoforms specifies a trans-synaptic signaling code.

Alternative Splicing↗
PubMed2004

Altered regulation of brain-derived neurotrophic factor protein in hippocampus following slice preparation.

Brain-derived neurotrophic factor (BDNF) and its cognate receptor tyrosine kinase B (TrkB) play important roles in regulating survival, structure, and function of CNS neurons. One method of studying the functions of these molecules has utilized in vitro hippocampal slice preparations. An important caveat to using slices, however, is that slice preparation itself might alter the expression of BDNF, thereby confounding experimental results. To address this concern, BDNF immunoreactivity was examined in rodent slices using two different methods of slice preparation. Rapid and anatomically selective regulation of BDNF content followed slice preparation using both methodologies; however, different patterns of altered BDNF immunoreactivity were observed. First, in cultured slices, BDNF content decreased in the dentate molecular layer and increased in the CA3 pyramidal cell layer and the mossy fiber pathway of the hippocampus after 30 min. Furthermore, an initially "punctate" pattern of BDNF labeling observed in the mossy fiber pathway of control sections changed to homogenous labeling of the pathway in vitro. In contrast to these findings, slices prepared as for acute slice physiology exhibited no change in BDNF content in the molecular layer and mossy fiber pathway 30 min after slicing, but exhibited significant increases in the dentate granule and CA3 pyramidal cell layers. These findings demonstrate that BDNF protein content is altered following slice preparation, that different methods of slice preparation produce different patterns of BDNF regulation, and raise the possibility that BDNF release and TrkB activation may also be regulated. These consequences of hippocampal slice preparation may confound analyses of exogenous or endogenous BDNF on hippocampal neuronal structure or function.

Analysis of Variance↗
PubMed2005

Modulation of neurotransmitter release by the second messenger-activated protein kinases: implications for presynaptic plasticity.

Activity-dependent modulation of synaptic function and structure is emerging as one of the key mechanisms underlying synaptic plasticity. Whereas over the past decade considerable progress has been made in identifying postsynaptic mechanisms for synaptic plasticity, the presynaptic mechanisms involved have remained largely elusive. Recent evidence implicates that second messenger regulation of the protein interactions in synaptic vesicle release machinery is one mechanism by which cellular events modulate synaptic transmission. Thus, identifying protein kinases and their targets in nerve terminals, particularly those functionally regulated by synaptic activity or intracellular [Ca2+], is critical to the elucidation of the molecular mechanisms underlying modulation of neurotransmitter release and presynaptic plasticity. The phosphorylation and dephosphorylation states of synaptic proteins that mediate vesicle exocytosis could regulate the biochemical pathways leading from synaptic vesicle docking to fusion. However, functional evaluation of the activity-dependent phosphorylation events for modulating presynaptic functions still represents a considerable challenge. Here, we present a brief overview of the data on the newly identified candidate targets of the second messenger-activated protein kinases in the presynaptic release machinery and discuss the potential impact of these phosphorylation events in synaptic strength and presynaptic plasticity.

Animals↗
PubMed2002

Gender differences in steroid modulation of angiotensin II-induced protein kinase C activity in anterior pituitary of the rat.

To investigate whether the various steroid hormones can modulate the basal and angiotensin II-induced protein kinase C (PKC) activity in the anterior pituitary of the rat, female and male intact and ovariectomized female Wistar rats were treated in vivo with estradiol (E2), progesterone (P), dehydroepiandrostendione sulfate (DHEA-S), and pregnenolone sulfate (PREG-S). Estradiol caused the increase of basal PKC activity in intact and ovariectomized females, but did not change the enzyme activity in males. In ovariectomized animals the increase of PKC activity was lower than in intact females. Progesterone decreased PKC activity only in intact animals. DHEA-S strongly enhanced activity of PKC in ovariectomized females. Pregnenolone sulfate did not significantly change PKC function of all studied groups. Incubation with AngII enhanced the PKC activity in intact (without steroid treatment) animals of both genders. In females, AngII and estradiol together rise the PKC-stimulated phosphorylation in greater degree than used separately. Treatment with other investigated steroids reduced the effect of AngII. In intact males every examined hormone turned back the stimulatory effect of AngII on PKC activity. These data suggest that gender differences in PKC activity are likely related to hormonal milieu of experimental animals and may depend in part on the basic plasma level of estrogens.

Angiotensin II↗
PubMed1986

Inhibition of phospholipase A2 by protein I.

The 36 kDa substrate of several tyrosine protein kinases has been shown to exist in monomeric and oligomeric (362102) forms. Partial sequence data has suggested that the oligomer, referred to as protein I, is homologous to a group of phospholipase A2 inhibitory proteins, collectively called lipocortins. In the present communication we demonstrate that protein I inhibits bovine pancreas phospholipase A2 with similar potency to that of lipocortin. Approximately 44 pmol protein I was required to produce 50% inhibition of 7.2 pmol of phospholipase A2. Inhibition of phospholipase A2 activity by calmodulin, S-100, calregulin, parvalbumin, troponin-C, or CAB-48 was not observed. These results indicate that protein I is a potent and specific inhibitor of phospholipase A2 activity, and thus shares functional homology with the lipocortin proteins. We therefore propose that this protein be named lipocortin-85.

Amino Acid Sequence↗
PubMed2003

Thyroid hormones in the rat amygdala as common targets for antidepressant drugs, mood stabilizers, and sleep deprivation.

BACKGROUND: There have been repeated reports of antidepressant effects of thyroid hormones. In this study, we investigated whether antidepressant treatments enhance the concentrations of thyroid hormones in rat brain. METHODS: Each of the groups of rats was treated for 14 days with one of the following: an antidepressant drug (desipramine, paroxetine, venlafaxine, or tianeptine); a mood stabilizer (lithium or carbamazepine); or 8 hours' partial sleep deprivation. Thyroid hormone concentrations were quantified in homogenates, nuclei, mitochondria, synaptosomes, myelin, and microsomes in 11 rat brain areas. RESULTS: No drug effects were seen on nuclear triiodothyronine (T(3)) concentrations in any brain area. In the amygdala, all antidepressant drugs enhanced the levels of T(3) in the myelin fraction. Triiodothyronine molecules were identified in the myelin by immunogold labeling. Quantification of the major lipid components showed a selective decrease in cholesterol in the myelin of the amygdala after desipramine treatment. Desipramine induced an increase in protein concentrations, 3,5-diiodothyronine levels, and the activity of the mitochondrial enzyme succinate dehydrogenase in the mitochondria of the amygdala. Lithium, carbamazepine, and partial sleep deprivation raised the levels of T(3) in synaptosomes of the amygdala. CONCLUSIONS: These results demonstrate that thyroid hormones in the amygdala are a common target of different antidepressant and mood-stabilizing therapies.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2000

Coordinate enrichment of cranin (dystroglycan) subunits in synaptic membranes of sheep brain.

Cranin (dystroglycan), a mucin-like extracellular matrix receptor comprised of two subunits (alpha and beta), is involved in regulating cell-matrix interactions in a variety of tissues, including brain. A basic issue remains unresolved concerning the distribution of cranin in brain: are the alpha and beta subunits coordinately expressed at the synapse? We report here that cranin is indeed enriched progressively in synaptosomes and synaptic membranes of sheep brain, as assessed by immunoblotting and laminin-blotting assays, and that the extent of enrichment is similar for both alpha and beta subunits. These findings support the hypothesis that cranin (dystroglycan) contributes to synaptic function in the CNS.

Animals↗
PubMed1999

Metalloprotease MP100: a synaptic protease in rat brain.

Proteases are expressed widely throughout the nervous system and perform essential functions. We have earlier characterized and cloned the metalloprotease MP100, an enzyme originally described as a beta-amyloid precursor protein (beta-APP) processing candidate. In the present study we describe the cellular and subcellular localization of MP100 in rat brain. A punctuate intracellular immunostaining in cortical, hippocampal and cerebellar neurons suggests its high abundance in vesicular intracellular structures. The MP100 staining pattern resembled that of the presynaptic protein synaptophysin. In gel filtration chromatography of isolated rat brain synaptosomal membranes, MP100 co-fractionated with synaptophysin and beta-APP. Furthermore, pre-embedding immunoelectron microscopy of the cerebellum revealed MP100 to be localized at synaptic sites. All together, these data might indicate a role for MP100 in functions such as proteolytic modification of synaptic proteins.

Animals↗
PubMed1980

Neuronal protein phosphorylation: recent studies concerning protein I, a synapse-specific phosphoprotein.

Recent studies are described concerning the physiological role and tissue distribution of Protein I, a synapse-specific phosphoprotein. This protein is present in both the central and the peripheral nervous system and appears to be enriched in synaptic vesicles. It is a major substrate for both Ca2(-)- and cyclic AMP-dependent phosphorylation in the brain. In slices of the facial motor nucleus from rat brainstem, serotonin (5-HT) added to the incubation medium stimulates the phosphorylation of Protein I. This effect is potentiated by low concentrations of isobutylmethylxanthine and is prevented by the serotonin antagonist mianserin.

Animals↗
PubMed2003

Seven cDNAs enriched following hippocampal lesion: possible roles in neuronal responses to injury.

Synaptic plasticity is important for formation of long-term memories and in re-establishment of function following injury. Seven cDNAs enriched following lesion in the hippocampus of the rat have been isolated using a PCR-based cDNA suppression subtraction hybridization. Sequence analysis resulted in the identification of two genes with known roles in synaptic development and neuronal activities: astrotactin and calcineurin. These two neuron-specific genes have established roles in development or synaptogenesis. Sequence analysis of the other five additional genes shows that two are likely to be involved in G-protein signaling pathways, one is a WD repeat protein, and the remaining two are entirely novel. All seven candidates are expressed in the hippocampus and, in some cases, cortical layers of adult brains. RT-PCR data show that expression increases following synaptogenic lesion. Immunocytochemical analysis in primary hippocampal neurons showed that Calcineurin immunoreactivity was redistributed in neurons during 2 weeks in culture. This redistribution suggests that Calcineurin's role changes during neurite outgrowth immediately prior to synapse formation in vitro. In addition, inhibiting Calcineurin activity with cyclosporin A enhanced neurite outgrowth, suggesting that Calcineurin has a regulatory role in axon sprouting. The discovery of previously unknown genes involved in the response to neurodegeneration will contribute to our understanding of neural development, responses to CNS trauma, and neurodegenerative diseases.

Animals↗
PubMed1999

Differential effects of GDNF and BDNF on cultured ventral mesencephalic neurons.

Previous studies have shown that brain derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) can enhance the survival of dopaminergic neurons in the ventral mesencephalon (VM). Here we compared several non-survival functions of the two factors in VM neurons in culture. We found that both BDNF and GDNF elicited an increase in the depolarization-induced release of dopamine, but had no effect on GABA release, in the VM cultures. BDNF, but not GDNF, significantly enhanced the expression of the calcium binding protein calbindin and synaptic protein SNAP25. In contrast, treatment of the cultures with GDNF, but not BDNF, elicited a marked fasciculation of the processes of the VM neurons. Thus, although both act on VM neurons, BDNF and GDNF have distinct functions.

Actins↗
PubMed1998

Changes in dendritic structure and function following hippocampal lesions: correlations with developmental events?

Recovery after nervous system lesions may lead to partial re-institution of developmental schemes and processes. Here we review several of these proposed schemes, with the conclusion that though some processes may involve re-expression of embryonic phenotypes, there are many processes invoked during recovery from lesions that do not mirror developmental phenomena. The inability to fully revert to embryonic schemes because of adult phenotype may partially account for the decreased recovery observed in adults compared to that noted after lesions during development.

Animals↗