The Experts below are selected from a list of 6522 Experts worldwide ranked by ideXlab platform
Stephen Welle - One of the best experts on this subject based on the ideXlab platform.
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Sympathetic nervous system response to intake
The American Journal of Clinical Nutrition, 1995Co-Authors: Stephen WelleAbstract:Meals increase the activity of the sympathetic nervous system (SNS) above the activity level observed in the postabsorptive state. Pharmacologic blockade of the thermogenic effect of norepinephrine, the Primary Neurotransmitter of the SNS, suggests that this response accounts for 20% of the thermic response to food. Energy expenditure increases after several days of sustained overeating. There is no convincing evidence that this response is mediated by increased SNS activity in humans, as it is in some animals. Energy expenditure decreases within a few days of energy deprivation. When sodium balance is maintained, energy deprivation also reduces SNS activity. The reduced SNS activity may contribute to the decreased energy expenditure, but cannot explain it completely. The contribution of the SNS to total energy expenditure is small in normal subjects consuming a weight-maintenance diet, probably < 5%. A few studies have suggested that SNS activity is reduced in obese humans, suggesting that low energy expenditure associated with reduced SNS activity may contribute to obesity. However, a critical evaluation of the available evidence indicates that this hypothesis is untenable.
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Sympathetic nervous system response to intake.
The American journal of clinical nutrition, 1995Co-Authors: Stephen WelleAbstract:Meals increase the activity of the sympathetic nervous system (SNS) above the activity level observed in the postabsorptive state. Pharmacologic blockade of the thermogenic effect of norepinephrine, the Primary Neurotransmitter of the SNS, suggests that this response accounts for approximately 20% of the thermic response to food. Energy expenditure increases after several days of sustained overeating. There is no convincing evidence that this response is mediated by increased SNS activity in humans, as it is in some animals. Energy expenditure decreases within a few days of energy deprivation. When sodium balance is maintained, energy deprivation also reduces SNS activity. The reduced SNS activity may contribute to the decreased energy expenditure, but cannot explain it completely. The contribution of the SNS to total energy expenditure is small in normal subjects consuming a weight-maintenance diet, probably < 5%. A few studies have suggested that SNS activity is reduced in obese humans, suggesting that low energy expenditure associated with reduced SNS activity may contribute to obesity. However, a critical evaluation of the available evidence indicates that this hypothesis is untenable.
Nathalie C Guerineau - One of the best experts on this subject based on the ideXlab platform.
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cholinergic and peptidergic neurotransmission in the adrenal medulla a dynamic control of stimulus secretion coupling
Iubmb Life, 2020Co-Authors: Nathalie C GuerineauAbstract:Synaptic neurotransmission at the splanchnic nerve-chromaffin cell synapse is a chief element of the stimulus-secretion coupling in the adrenal medullary tissue, managing and regulating the secretion of catecholamines. Making the state of play more intricate than initially envisioned, the synaptic vesicles of nerve terminals innervating the medulla contain various compounds, including various Neurotransmitters and neuropeptides. Under basal conditions associated with a low splanchnic nerve discharge rate, neurotransmission is ensured by the synaptic release of the Primary Neurotransmitter acetylcholine (ACh). Under sustained and repetitive stimulations of the splanchnic nerve, as triggered in response to stressors, the synaptic release of neuropeptides, such as the pituitary adenylate cyclase-activating polypeptide PACAP, supplants ACh release. The anatomical and functional changes that occur presynaptically at the preganglionic splanchnic nerve, combined with changes occurring postsynaptically at nicotinic acetylcholine receptors (nAChRs), confer the adrenomedullary synapses a solid and persistent aptitude to functional remodeling, from birth to aging. The present review focuses on the composite cholinergic and noncholinergic nature of neurotransmission occurring at the splanchnic nerve-chromaffin cell synapse and its remodeling in response to physiological or pathological stimuli.
Amalendu Chandra - One of the best experts on this subject based on the ideXlab platform.
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Conformation-Induced Dynamical Heterogeneity of Water in the Solvation Shell of Zwitterionic γ-Aminobutyric Acid
The journal of physical chemistry. B, 2019Co-Authors: Bikramjit Sharma, Amalendu ChandraAbstract:The structure and dynamics of water molecules around the carboxylate and amino groups of γ-aminobutyric acid (GABA), a Primary Neurotransmitter in mammals, are investigated by means of ab initio molecular dynamics simulation. Zwitterionic GABA has two major conformations in water, namely, the open and the closed conformations. The angle-averaged one-dimensional structures of water in the solvation shells around the carboxylate and amino groups are found to be quite similar for the closed and open conformations of the solute. The two-dimensional structural correlations, which describe the solvation shell structure with better resolution, reveal some differences in the arrangement of water molecules around the solute for its open and closed conformations. It is found that the dynamics of solvation shells in the two conformations vary only slightly. However, the existence of trapped water between the oppositely charged carboxylate and amino groups of GABA in its closed form is found to give rise to a very di...
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On the issue of closed versus open forms of gamma-aminobutyric acid (GABA) in water: Ab initio molecular dynamics and metadynamics studies
The Journal of chemical physics, 2018Co-Authors: Bikramjit Sharma, Amalendu ChandraAbstract:Gamma-aminobutyric acid (GABA), a Primary Neurotransmitter, accomplishes its activities by binding to different receptor sites in different conformations. It is known to have two major conformers: the closed and open forms. Earlier studies on preferred conformation of GABA in water revealed differing results with some reporting the open form while others inferring the closed form to be more stable. We found the existence of many open forms and only one closed form of GABA in water through ab initio metadynamics simulation. Some of the open conformers are equally or more stable while others are less stable than the closed form. Free energy barriers reveal that different conformers are interconvertible at room temperature in typical experimental time scales. Ab initio molecular dynamics simulations are performed to further investigate the inter-conversion of various conformers of GABA in water and their dipole moments and also to make connections to experiments on the conformation of GABA in water.
J L Seagard - One of the best experts on this subject based on the ideXlab platform.
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Presence of glutamate receptor subtypes on barosensitive neurons in the nucleus tractus solitarius of the dog.
Neuroscience letters, 1999Co-Authors: S A Botsford, C Dean, F A Hopp, J L SeagardAbstract:Afferent baroreceptor information is transmitted to the nucleus tractus solitarius (NTS) in the dorsal medulla where glutamate is thought to be the Primary Neurotransmitter. However, the subtypes of glutamate receptors involved in the baroreflex remain to be established. The present study compared the distribution of immunohistochemically labeled ionotropic receptor subtypes to the distribution of physiologically stimulated barosensitive neurons in the NTS of the dog and also identified ionotropic receptor subtypes located on barosensitive neurons. Both NMDA and non-NMDA receptors were located in barosensitive areas and on barosensitive neurons, suggesting that both may be involved in the baroreflex.
Gerard Sanacora - One of the best experts on this subject based on the ideXlab platform.
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The stressed synapse: the impact of stress and glucocorticoids on glutamate transmission
Nature Reviews Neuroscience, 2012Co-Authors: Maurizio Popoli, Bruce S. Mcewen, Gerard SanacoraAbstract:Recent studies have shed light on the mechanisms by which stress and glucocorticoids affect glutamate transmission in the prefrontal cortex and the hippocampus. Sanacora and colleagues review these studies and discuss the relevance of these mechanisms for normal brain functioning and for the pathophysiology and potential new treatments of stress-related neuropsychiatric disorders. Mounting evidence suggests that acute and chronic stress, especially the stress-induced release of glucocorticoids, induces changes in glutamate neurotransmission in the prefrontal cortex and the hippocampus, thereby influencing some aspects of cognitive processing. In addition, dysfunction of glutamatergic neurotransmission is increasingly considered to be a core feature of stress-related mental illnesses. Recent studies have shed light on the mechanisms by which stress and glucocorticoids affect glutamate transmission, including effects on glutamate release, glutamate receptors and glutamate clearance and metabolism. This new understanding provides insights into normal brain functioning, as well as the pathophysiology and potential new treatments of stress-related neuropsychiatric disorders. Excitatory synapses in the brain, which use glutamate as the Primary Neurotransmitter, represent a crucial target for the action of stress and its mediators. Mounting evidence suggests that stress, along with the associated hormonal and neurochemical mediators (particularly glucocorticoids), induces changes in glutamate release, transmission and metabolism in cortical and limbic brain areas, thereby influencing cognitive and emotional processing and behaviour. Depending on age, gender, duration and the type of the stressors experienced, stress may either have beneficial effects on cognitive and emotional functions or induce noxious and maladaptive changes in brain tissue, which have been linked to the development of neuropsychiatric disorders. Acute stress enhances glutamatergic synaptic transmission in the prefrontal cortex and other limbic regions, thereby facilitating certain cognitive functions. Acute stress increases glutamate release, membrane trafficking of AMPA and NMDA receptors, and potentially glutamate clearance in the prefrontal cortex through various mechanisms that involve glucocorticoid regulation. Chronic stress has been associated with a loss of glutamate receptors, impaired glutamate cycling and a suppression of glutamate transmission that may be attributable to the observed impairment of prefrontal cortex-dependent cognitive functions. These findings suggest that a new line of drug development aimed at minimizing the effects of chronic stress exposure on the function of the glutamatergic Neurotransmitter system may prove beneficial in clinical settings. Straightforward pharmacological intervention on different regulatory sites of the glutamate synapse is a possible strategy for bypassing the unmet therapeutic needs posed by traditional drugs based on monoaminergic mechanisms.