Metabolic and serotonergic modulation of hypothalamic arcuate nucleus neurones in vitro

1. The effects of glucose on the electrophysiological properties of rat hypothalamic arcuate nucleus (ARC) neurones were investigated. Neurones were recorded in 10 mM (hyperglycaemic) and 2 mM (euglycaemic) glucose-containing aCSF. The major findings were that input resistance increased in 10 mM glucose, there was an increase in the activity of neurones in 2 mM glucose and there were a greater percentage of neurones expressing lh in 10 mM glucose. Subthreshold active conductances were differentially expressed in ARC neurones including: anomalous inward rectification Q. ), time- and voltage-dependent inward rectification 00, A-like transient outward rectification (IA) and T-type calcium-like conductance. Characterisation of the differential expression of these conductances may represent one way of functionally classifying ARC neurones. 2. Whole-cell patch clamp recording techniques were used in isolated hypothalamic brain slice preparations to investigate the effects of 5-HT on ARC neurones. Bath application of 5-HT induced a membrane depolarisation in a sub-population of ARC neurones (30%), a response that persisted in the presence of TTX indicating a direct effect. 5-HT excited ARC neurones through three potential mechanisms: closure of one or more resting potassium conductances; activation of a non-selective cation channel, or a combination of the two; or activation of a pump in the membrane. This response was mediated through the 5-HT2A. 5-HT2B and/or 5-HT2C receptors revealed using a range of 5-HT receptor agonists and antagonists. 5-HT was shown to excite CART-expressing neurones suggesting an anorexigenic role for 5-HT, via 5-HT2 receptors at the level of the ARC. 3.5-HT induced a membrane hyperpolarisation in a sub-population of ARC neurones (37%). The 5-HT-induced hyperpolarisation persisted in the presence of TTX indicating a direct effect on ARC neurones. 5-HT inhibited ARC neurones most likely through the activation of one or more potassium conductances,including an inwardly rectifying potassium conductance. Potential roles for 5-HTIA, 5-HTIB and 5-HT7 receptors were suggested from studies utilising 5-HT receptor agonists and antagonists. 5-HT inhibited orexigenic NPY/AgRP neurones, identified by their response to ghrelin and by their electrophysiological properties, suggesting an anorexigenic role for 5-HT, acting via 5-HTI and 5-HT7 receptors on NPY/AgRP neurones at the level of the ARC. 4. The effects of feeding-related signals on hypothalamic neuropeptide expression were investigated using real-time-PCR. A new protocol measuring gene expression from hypothalamic explants was developed. Effects of GABA and AMPA on c-fos expression were investigated and subsequent studies showed leptin and glucose modulated the expression of NPY, POMC and AgRP, in fed and fasted animals. Further work is required to validate this novel approach to studying the central control of energy balance

Metabolic and serotonergic modulation of hypothalamic arcuate nucleus neurones in vitro

1. The effects of glucose on the electrophysiological properties of rat hypothalamic arcuate nucleus (ARC) neurones were investigated. Neurones were recorded in 10 mM (hyperglycaemic) and 2 mM (euglycaemic) glucose-containing aCSF. The major findings were that input resistance increased in 10 mM glucose, there was an increase in the activity of neurones in 2 mM glucose and there were a greater percentage of neurones expressing lh in 10 mM glucose. Subthreshold active conductances were differentially expressed in ARC neurones including: anomalous inward rectification Q. ), time- and voltage-dependent inward rectification 00, A-like transient outward rectification (IA) and T-type calcium-like conductance. Characterisation of the differential expression of these conductances may represent one way of functionally classifying ARC neurones. 2. Whole-cell patch clamp recording techniques were used in isolated hypothalamic brain slice preparations to investigate the effects of 5-HT on ARC neurones. Bath application of 5-HT induced a membrane depolarisation in a sub-population of ARC neurones (30%), a response that persisted in the presence of TTX indicating a direct effect. 5-HT excited ARC neurones through three potential mechanisms: closure of one or more resting potassium conductances; activation of a non-selective cation channel, or a combination of the two; or activation of a pump in the membrane. This response was mediated through the 5-HT2A. 5-HT2B and/or 5-HT2C receptors revealed using a range of 5-HT receptor agonists and antagonists. 5-HT was shown to excite CART-expressing neurones suggesting an anorexigenic role for 5-HT, via 5-HT2 receptors at the level of the ARC. 3.5-HT induced a membrane hyperpolarisation in a sub-population of ARC neurones (37%). The 5-HT-induced hyperpolarisation persisted in the presence of TTX indicating a direct effect on ARC neurones. 5-HT inhibited ARC neurones most likely through the activation of one or more potassium conductances,including an inwardly rectifying potassium conductance. Potential roles for 5-HTIA, 5-HTIB and 5-HT7 receptors were suggested from studies utilising 5-HT receptor agonists and antagonists. 5-HT inhibited orexigenic NPY/AgRP neurones, identified by their response to ghrelin and by their electrophysiological properties, suggesting an anorexigenic role for 5-HT, acting via 5-HTI and 5-HT7 receptors on NPY/AgRP neurones at the level of the ARC. 4. The effects of feeding-related signals on hypothalamic neuropeptide expression were investigated using real-time-PCR. A new protocol measuring gene expression from hypothalamic explants was developed. Effects of GABA and AMPA on c-fos expression were investigated and subsequent studies showed leptin and glucose modulated the expression of NPY, POMC and AgRP, in fed and fasted animals. Further work is required to validate this novel approach to studying the central control of energy balance.EThOS - Electronic Theses Online ServiceBiotechnology and Biological Sciences Research Council (Great Britain) (BBSRC)GBUnited Kingdo

Metabolic and serotonergic modulation of hypothalamic arcuate nucleus neurones in vitro

1. The effects of glucose on the electrophysiological properties of rat hypothalamic arcuate nucleus (ARC) neurones were investigated. Neurones were recorded in 10 mM (hyperglycaemic) and 2 mM (euglycaemic) glucose-containing aCSF. The major findings were that input resistance increased in 10 mM glucose, there was an increase in the activity of neurones in 2 mM glucose and there were a greater percentage of neurones expressing lh in 10 mM glucose. Subthreshold active conductances were differentially expressed in ARC neurones including: anomalous inward rectification Q. ), time- and voltage-dependent inward rectification 00, A-like transient outward rectification (IA) and T-type calcium-like conductance. Characterisation of the differential expression of these conductances may represent one way of functionally classifying ARC neurones. 2. Whole-cell patch clamp recording techniques were used in isolated hypothalamic brain slice preparations to investigate the effects of 5-HT on ARC neurones. Bath application of 5-HT induced a membrane depolarisation in a sub-population of ARC neurones (30%), a response that persisted in the presence of TTX indicating a direct effect. 5-HT excited ARC neurones through three potential mechanisms: closure of one or more resting potassium conductances; activation of a non-selective cation channel, or a combination of the two; or activation of a pump in the membrane. This response was mediated through the 5-HT2A. 5-HT2B and/or 5-HT2C receptors revealed using a range of 5-HT receptor agonists and antagonists. 5-HT was shown to excite CART-expressing neurones suggesting an anorexigenic role for 5-HT, via 5-HT2 receptors at the level of the ARC. 3.5-HT induced a membrane hyperpolarisation in a sub-population of ARC neurones (37%). The 5-HT-induced hyperpolarisation persisted in the presence of TTX indicating a direct effect on ARC neurones. 5-HT inhibited ARC neurones most likely through the activation of one or more potassium conductances,including an inwardly rectifying potassium conductance. Potential roles for 5-HTIA, 5-HTIB and 5-HT7 receptors were suggested from studies utilising 5-HT receptor agonists and antagonists. 5-HT inhibited orexigenic NPY/AgRP neurones, identified by their response to ghrelin and by their electrophysiological properties, suggesting an anorexigenic role for 5-HT, acting via 5-HTI and 5-HT7 receptors on NPY/AgRP neurones at the level of the ARC. 4. The effects of feeding-related signals on hypothalamic neuropeptide expression were investigated using real-time-PCR. A new protocol measuring gene expression from hypothalamic explants was developed. Effects of GABA and AMPA on c-fos expression were investigated and subsequent studies showed leptin and glucose modulated the expression of NPY, POMC and AgRP, in fed and fasted animals. Further work is required to validate this novel approach to studying the central control of energy balance.EThOS - Electronic Theses Online ServiceBiotechnology and Biological Sciences Research Council (Great Britain) (BBSRC)GBUnited Kingdo

The role of tacit knowledge sharing in national sales companies

The role of tacit knowledge sharing in national sales companie

Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60-80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies

Mapping genomic loci prioritises genes and implicates synaptic biology in schizophrenia

Schizophrenia has a heritability of 60–80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies

Why Kuwait will listen to Costa Rica but not vice versa: The role of 'Organizational Homophily' in tacit knowledge sharing between national sales companies

Why Kuwait will listen to Costa Rica but not vice versa: The role of 'Organizational Homophily' in tacit knowledge sharing between national sales companie

Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60-80%(1), much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factorSP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies

Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60-80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies.11Nsciescopu

Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60–80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies