The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Istvan Merchenthaler - One of the best experts on this subject based on the ideXlab platform.
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Catecholaminergic System innervates galanin-immunoreactive neurons in the human diencephalon
Neuroscience, 2013Co-Authors: Istvan Merchenthaler, G. Rotoli, M. Peroski, George Grignol, Bertalan DudasAbstract:Galanin released into the hypophysial portal circulation in the hypothalamus may function as a hypophysiotropic factor regulating the anterior pituitary function or it may function as a neurotransmitter/neuromodulator acting at synaptic sites regulating neuronal activity of many neurons in the brain. Catecholamines (adrenaline, noradrenaline, and dopamine) primarily regulate anterior pituitary functions indirectly via innervating hypophysiotropic neurons. The aim of the present studies was to explore with double-label immunocytochemistry if, as in rodents, catecholamines interact with galanin in the human diencephalon. Due to the long post-mortem period and subsequent lack of optimal preservation of the cell membranes in the brain, electron microscopy could not be employed to show the presence of Catecholaminergic-immunoreactive synapses on galanin-immunoreactive neurons. Therefore, we used light microscopic immunocytochemistry and high-magnification microscopy with oil immersion to identify putative juxtapositions between catecholamines and galanin-utilizing antisera against key enzymes of catecholamine synthesis (tyrosine hydroxylase (TH), representing all three catecholamines; dopamine-beta-hydroxylase (DBH), representing noradrenaline; and phenylethanolamine-N-methyltransferase (PNMT), representing adrenaline) and galanin. Our studies show that among the three catecholamines, dopamine is the most abundant and the vast majority of Catecholaminergic contacts on galanin-immunoreactive neurons is dopaminergic. The number of DBH-immunoreactive contacts is less and the number of PNMT-immunopositive contacts is negligible. Among the hypothalamic regions, the periventricular region above the infundibulum (infundibular or arcuate nucleus) contained the largest number of contacts. These en passant-type intimate associations between catecholamine- and galanin-immunoreactive neuronal elements may be functional synapses and may provide the morphological basis for the catecholamine-mediated galanin release.
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morphological substrate of the Catecholaminergic input of the vasopressin neuronal System in humans
Journal of Neuroendocrinology, 2006Co-Authors: Bertalan Dudas, K Semeniken, Istvan MerchenthalerAbstract:It has been postulated that the stress response is associated with water balance via regulating vasopressin release. Nausea, surgical stress and insulin-induced hypoglycaemia were shown to stimulate vasopressin secretion in humans. Increased vasopressin release in turn induces water resorption through the kidneys. Although the mechanism of the stress-mediated vasopressin release is not entirely understood, it is generally accepted that catecholamines play a crucial role in influencing water balance by modulating the secretion of vasopressin. However, the morphological substrate of this modulation has not yet been established. The present study utilised double-label immunohistochemistry to reveal putative juxtapositions between tyrosine hydroxylase (TH)-immunoreactive (IR) Catecholaminergic System and the vasopressin Systems in the human hypothalamus. In the paraventricular and supraoptic nuclei, numerous vasopressin-IR neurones received TH-IR axon varicosities. Analysis of these juxtapositions with high magnification combined with oil immersion did not reveal any gaps between the contacted elements. In conclusion, the intimate associations between the TH-IR and vasopressin-IR elements may be functional synapses and may represent the morphological basis of vasopressin release modulated by stressors. Because certain vasopressin-IR perikarya receive no detectable TH innervations, it is possible that additional mechanisms may participate in the stress-influenced vasopressin release.
Bertalan Dudas - One of the best experts on this subject based on the ideXlab platform.
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Catecholaminergic System innervates galanin-immunoreactive neurons in the human diencephalon
Neuroscience, 2013Co-Authors: Istvan Merchenthaler, G. Rotoli, M. Peroski, George Grignol, Bertalan DudasAbstract:Galanin released into the hypophysial portal circulation in the hypothalamus may function as a hypophysiotropic factor regulating the anterior pituitary function or it may function as a neurotransmitter/neuromodulator acting at synaptic sites regulating neuronal activity of many neurons in the brain. Catecholamines (adrenaline, noradrenaline, and dopamine) primarily regulate anterior pituitary functions indirectly via innervating hypophysiotropic neurons. The aim of the present studies was to explore with double-label immunocytochemistry if, as in rodents, catecholamines interact with galanin in the human diencephalon. Due to the long post-mortem period and subsequent lack of optimal preservation of the cell membranes in the brain, electron microscopy could not be employed to show the presence of Catecholaminergic-immunoreactive synapses on galanin-immunoreactive neurons. Therefore, we used light microscopic immunocytochemistry and high-magnification microscopy with oil immersion to identify putative juxtapositions between catecholamines and galanin-utilizing antisera against key enzymes of catecholamine synthesis (tyrosine hydroxylase (TH), representing all three catecholamines; dopamine-beta-hydroxylase (DBH), representing noradrenaline; and phenylethanolamine-N-methyltransferase (PNMT), representing adrenaline) and galanin. Our studies show that among the three catecholamines, dopamine is the most abundant and the vast majority of Catecholaminergic contacts on galanin-immunoreactive neurons is dopaminergic. The number of DBH-immunoreactive contacts is less and the number of PNMT-immunopositive contacts is negligible. Among the hypothalamic regions, the periventricular region above the infundibulum (infundibular or arcuate nucleus) contained the largest number of contacts. These en passant-type intimate associations between catecholamine- and galanin-immunoreactive neuronal elements may be functional synapses and may provide the morphological basis for the catecholamine-mediated galanin release.
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morphological substrate of the Catecholaminergic input of the vasopressin neuronal System in humans
Journal of Neuroendocrinology, 2006Co-Authors: Bertalan Dudas, K Semeniken, Istvan MerchenthalerAbstract:It has been postulated that the stress response is associated with water balance via regulating vasopressin release. Nausea, surgical stress and insulin-induced hypoglycaemia were shown to stimulate vasopressin secretion in humans. Increased vasopressin release in turn induces water resorption through the kidneys. Although the mechanism of the stress-mediated vasopressin release is not entirely understood, it is generally accepted that catecholamines play a crucial role in influencing water balance by modulating the secretion of vasopressin. However, the morphological substrate of this modulation has not yet been established. The present study utilised double-label immunohistochemistry to reveal putative juxtapositions between tyrosine hydroxylase (TH)-immunoreactive (IR) Catecholaminergic System and the vasopressin Systems in the human hypothalamus. In the paraventricular and supraoptic nuclei, numerous vasopressin-IR neurones received TH-IR axon varicosities. Analysis of these juxtapositions with high magnification combined with oil immersion did not reveal any gaps between the contacted elements. In conclusion, the intimate associations between the TH-IR and vasopressin-IR elements may be functional synapses and may represent the morphological basis of vasopressin release modulated by stressors. Because certain vasopressin-IR perikarya receive no detectable TH innervations, it is possible that additional mechanisms may participate in the stress-influenced vasopressin release.
Jacques Balthazart - One of the best experts on this subject based on the ideXlab platform.
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the Catecholaminergic System of the quail brain immunocytochemical studies of dopamine beta hydroxylase and tyrosine hydroxylase
The Journal of Comparative Neurology, 1993Co-Authors: Thierry Bailhache, Jacques BalthazartAbstract:The distribution of dopamine β-hydroxylase and tryrosine hydroxylase, two key enzymes in the biosynthesis of catecholamine, was investigated by immunocytochemistry in the brain of male and female Japanese quail. Cells or fibers showing dopamine β-hydroxylase and tyrosine hydroxylase immunoreactivity were considered to be noradrenergic or adrenergic, while all structures showing only tyrosine hydroxylase immunoreactivity were tentatively considered to be dopaminergic. The major dopaminergic and noradrenergic cell groups that have been identified in the brain of mammals could be observed in the Japanese quail, with the exception of a tuberoinfundibular dopaminergic group. The dopamine β-hydroxylase-immunoreactive cells were found exclusively in the pons (locus ceruleus and nucleus subceruleus ventralis) and in the medulla (area of the nucleus reticularis). The tyrosine hydroxylase-immunoreactive cells had a much wider distribution and extended from the preoptic area to the level of the medulla. They were, however, present in larger numbers in the area ventralis of Tsai and in the nucleus tegmenti pedunculo-pontinus, pars compacta, which respectively correspond to the ventral tegmental area and to the substantia nigra of mammals. A high density of dopamine β-hydroxylase- and tyrosine hydroxylase-immunoreactive fibers and punctate structures was found in several steroid-sensitive brain regions that are implicated in the control of reproduction. In the preoptic area and in the region of the nucleus accumbens-nucleus stria terminalis, immunonegative perikarya were completely surrounded by immunoreactive fiber forming basket-like structures. Given that some of these cells contain the enzyme aromatase, these structures may represent the morphological substrate for a regulation of aromatase activity by catecholamines. The dopamine β-hydroxylase-immunoreactive fibers were also present in a larger part of the preoptic area of females than in males. This sex difference in the noradrenergic innervation of the preoptic area presumably reflects the sex difference in norepinephrine content in this region. © 1993 Wiley-Liss, Inc.
David S. Goldstein - One of the best experts on this subject based on the ideXlab platform.
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Novel Catecholaminergic Systems
Advances in Pharmacology, 1997Co-Authors: David S. GoldsteinAbstract:Publisher Summary This chapter summarizes several studies on novel Catecholaminergic Systems. The researches are related to catecholestrogens, nonneuronal biosynthesis of catecholamines, L-dopa as a neurotransmitter, and dopamine (DA) as a renal autocrineparacrine substance. Production of 2-hydroxylated catecholestrogens (2-OH-CEs) constitutes a major pathway for hepatic metabolism of estrone (E 1 ) and estradiol (E 2 ). Aromatic hydroxylation of E 2 by estradiol-2/4 hydroxylase yields the catecholestrogens 2-OH-E 2 and 4-OH-E 2 . In human breast cancer microsomes, 4-OH-E 2 constitutes a major catechol metabolite, consistent with a role of CEs in production of estrogen-dependent tumors. CEs also appear to play an important role in blastocyst implantation. Investigators have viewed DA as only an intermediary in the biosynthesis of norepinephrine (NE) in sympathetic nerves and of epinephrine (Epi) in adrenomedullary cells. Recent evidence has supported a physiological role for DA as an autocrine-paracrine hormone that influences Na + disposition in the periphery. L-Dopa undergoes conversion to DA in many types of cells, including neurons, and DA acts as a classical central neurotransmitter. In the nucleus of the solitary tract (NTS), L-dopa may modulate the arterial baroreflex. The renal DOPA-DA System constitutes the most well studied nonneuronal Catecholaminergic System. L-dopa in the tubular filtrate undergoes Na + - dependent uptake into proximal tubular cells. Classical endocrine Systems may contribute to regulation of the renal DOPA-DA natriuretic System. The studies support the view that the renal DOPA-DA System mediates some hormonal influences on renal sodium handling.
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Is There a Third Peripheral Catecholaminergic System? Endogenous Dopamine as an Autocrine/ Paracrine Substance Derived from Plasma DOPA and Inactivated by Conjugation
Hypertension Research, 1995Co-Authors: David S. Goldstein, Eva Mezey, Toshimasa Yamamoto, Anders Aneman, Peter Friberg, Graeme EisenhoferAbstract:In mammals, the sympathetic neurotransmitter is norepinephrine (NE), and the main adrenomedullary hormone is epinephrine (EPI). The sources and physiological roles of the third endogenous catecholamine, dopamine (DA), outside the brain have been obscure. Several lines of evidence suggest that in the periphery, rather than DA serving only as the precursor for the active compounds, released from sympathetic nerves and the adrenal medulla, DA may also act as an autocrine/paracrine regulator of local organ function. Thus, in the kidneys, most of DA formation appears to be from proximal tubular uptake of plasma DOPA, and binding of locally formed DA to dopaminergic receptors decreases Na/K ATPase activity and thereby accentuates natriuresis. In the gastric mucosa, DA may modulate sodium absorption and acid secretion. Recent clinical and laboratory animal evidence has indicated that the lungs and mesenteric organs contribute substantially to total body production and metabolism of DA. Generation of DA in non-noradrenergic, non-adrenergic cells can explain why human urine contains higher concentrations of DA and its metabolites than of NE and its metabolites. The vast preponderance of plasma DA in humans is sulfoconjugated. Since patients with sympathoneural failure have normal plasma levels of DA sulfate, one may speculate that the sulfoconjugating mechanism is relatively independent of sympathetic nerves and acts to localize DA effects and inactivate DA entering the circulation. These considerations lead to the concept of a third peripheral Catecholaminergic System, where DA derived from plasma DOPA acts as an autocrine/paracrine substance and is inactivated by conjugation. (Hypertens Res 1995; 18 Suppl. I: S93-S99)
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Is there a third peripheral Catecholaminergic System? Endogenous dopamine as an autocrine/paracrine substance derived from plasma DOPA and inactivated by conjugation.
Hypertension research : official journal of the Japanese Society of Hypertension, 1995Co-Authors: David S. Goldstein, Eva Mezey, Toshimasa Yamamoto, Anders Aneman, Peter Friberg, Graeme EisenhoferAbstract:In mammals, the sympathetic neurotransmitter is norepinephrine (NE), and the main adrenomedullary hormone is epinephrine (EPI). The sources and physiological roles of the third endogenous catecholamine, dopamine (DA), outside the brain have been obscure. Several lines of evidence suggest that in the periphery, rather than DA serving only as the precursor for the active compounds, released from sympathetic nerves and the adrenal medulla, DA may also act as an autocrine/paracrine regulator of local organ function. Thus, in the kidneys, most of DA formation appears to be from proximal tubular uptake of plasma DOPA, and binding of locally formed DA to dopaminergic receptors decreases Na/K ATPase activity and thereby accentuates natriuresis. In the gastric mucosa, DA may modulate sodium absorption and acid secretion. Recent clinical and laboratory animal evidence has indicated that the lungs and mesenteric organs contribute substantially to total body production and metabolism of DA. Generation of DA in non-noradrenergic, non-adrenergic cells can explain why human urine contains higher concentrations of DA and its metabolites than of NE and its metabolites. The vast preponderance of plasma DA in humans is sulfoconjugated. Since patients with sympathoneural failure have normal plasma levels of DA sulfate, one may speculate that the sulfoconjugating mechanism is relatively independent of sympathetic nerves and acts to localize DA effects and inactivate DA entering the circulation. These considerations lead to the concept of a third peripheral Catecholaminergic System, where DA derived from plasma DOPA acts as an autocrine/paracrine substance and is inactivated by conjugation.
Thierry Bailhache - One of the best experts on this subject based on the ideXlab platform.
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the Catecholaminergic System of the quail brain immunocytochemical studies of dopamine beta hydroxylase and tyrosine hydroxylase
The Journal of Comparative Neurology, 1993Co-Authors: Thierry Bailhache, Jacques BalthazartAbstract:The distribution of dopamine β-hydroxylase and tryrosine hydroxylase, two key enzymes in the biosynthesis of catecholamine, was investigated by immunocytochemistry in the brain of male and female Japanese quail. Cells or fibers showing dopamine β-hydroxylase and tyrosine hydroxylase immunoreactivity were considered to be noradrenergic or adrenergic, while all structures showing only tyrosine hydroxylase immunoreactivity were tentatively considered to be dopaminergic. The major dopaminergic and noradrenergic cell groups that have been identified in the brain of mammals could be observed in the Japanese quail, with the exception of a tuberoinfundibular dopaminergic group. The dopamine β-hydroxylase-immunoreactive cells were found exclusively in the pons (locus ceruleus and nucleus subceruleus ventralis) and in the medulla (area of the nucleus reticularis). The tyrosine hydroxylase-immunoreactive cells had a much wider distribution and extended from the preoptic area to the level of the medulla. They were, however, present in larger numbers in the area ventralis of Tsai and in the nucleus tegmenti pedunculo-pontinus, pars compacta, which respectively correspond to the ventral tegmental area and to the substantia nigra of mammals. A high density of dopamine β-hydroxylase- and tyrosine hydroxylase-immunoreactive fibers and punctate structures was found in several steroid-sensitive brain regions that are implicated in the control of reproduction. In the preoptic area and in the region of the nucleus accumbens-nucleus stria terminalis, immunonegative perikarya were completely surrounded by immunoreactive fiber forming basket-like structures. Given that some of these cells contain the enzyme aromatase, these structures may represent the morphological substrate for a regulation of aromatase activity by catecholamines. The dopamine β-hydroxylase-immunoreactive fibers were also present in a larger part of the preoptic area of females than in males. This sex difference in the noradrenergic innervation of the preoptic area presumably reflects the sex difference in norepinephrine content in this region. © 1993 Wiley-Liss, Inc.