THE HYDROXYLATION of tyrosine by tyrosine hydroxylase (L-tyrosine, tetrahydropteridine: Oz oxidoreductase (2 hydroxylating); EC 1.14.3a) (LEVITT et al., 1965) and the 0-hydroxylation of dopamine by dopamine-p hydroxylase (EC 1.14.2.1)... more
THE HYDROXYLATION of tyrosine by tyrosine hydroxylase (L-tyrosine, tetrahydropteridine: Oz oxidoreductase (2 hydroxylating); EC 1.14.3a) (LEVITT et al., 1965) and the 0-hydroxylation of dopamine by dopamine-p hydroxylase (EC 1.14.2.1) (KAUFMAN & FRIEDMAN, 1965) are essential steps in the formation of the neurotransmitter noradrenaline. Tyrosine hydroxylase (MLJSACCHIO et af., 1969) and dopamine-p-hydroxylase (UNDENFRIEND & CREVELING, 1959) have been found to occur in brain, as well as in peripheral adrenergic nerves and in the adrenal medulla. Both enzymes (COYLE, 1972: REIS & MOLINOFF, 1972) are present in nerve terminals and are unevenly distributed in brain. Dopamine-P -hydroxylase is widely distributed in the central nervous system, with a pattern of regional distribution that parallels the levels of noradrenaline (REIS & MOLINOFF, 1972). It is probably produced in adrenergic cell bodies (AXELROD, 1972) and is concentrated in noradrenaline containing axon terminals. The highest dopamine-P-hydroxylase activity is measured in the brain stem and hypothalamus (COYLE & AXELROD, 1972). Tyrosine hydroxylase activity is highest in the striatum and in the hypothalamus (COYLE, 1972), regions with a high dopamine content (POPOV et al., 1967). The simultaneous development of a sensitive enzymatic-isotopic assay for dopamine and noradrenaline (COYLE & HENRY, 1973) and of a technique for removal of individual hypothalamic nuclei (PALKOVITS, 1973) has allowed us to determine the distribution of these catecholamines within the rat hypothalamus (PALKOVITS et a] . , 1974). Both amines were found to be unevenly distributed throughout the hypothalamus, and the individual nuclei were heterogeneous as regards their content of the amines. These observations together with the availability of sensitive methods for the measurement of tyrosine hydroxylase and dopamine-P-hydroxylase (COYLE, 1972; MOLINOFF et a!., 1971) prompted us to the study of the distribution of these enzymes in the rat hypothalamus. Sprague-Dawley male rats (Zivic Miller) weighing 20&250 g, were killed by decapitation and the brains were immediately removed and frozen on dry ice. Hypothalamic nuclei were removed from frozen serial sections of the brain according to the method of PALKOVITS ef af. (1974) with special stainless steel needles.
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Research Interests: Chemistry, Serotonin, Dopamine, Histamine, Humans, and 15 moreMethylation, Hypothalamus, Enzyme, Norepinephrine, Limbic System, Microchemistry, Psychiatric, Octopamine, Biogenic amines, Brain Chemistry, Methyltransferase, Phenethylamines, Psychology and Cognitive Sciences, Blood platelets, and Medical and Health Sciences
Research Interests: Endocrinology, Biology, Medicine, Dopamine, Internal Medicine, and 15 moreHypertension, Epinephrine, Blood Pressure, Animals, Male, Norepinephrine, Clinical Sciences, Rats, Circulation, Catecholamine, Catecholamines, Sodium Chloride, Adrenal glands, Medical and Health Sciences, and Cardiovascular medicine and haematology
Octopamine is a normally occurring amine in nervous tissues in many species of animals. In mammals, octopamine is formed from tyramine through beta-hydroxylation by DBH in the sympathetic nerves, and it is partially stored in nerve... more
Octopamine is a normally occurring amine in nervous tissues in many species of animals. In mammals, octopamine is formed from tyramine through beta-hydroxylation by DBH in the sympathetic nerves, and it is partially stored in nerve endings with a subcellular distribution similar to that of NE. It is capable of replacing NE in its storage sites, and it is released by sympathetic nerve stimulation. High concentrations are found in the crustacean central nerve cord. Specific octopamine-containing cells have been identified in Aplysia and other lower animals. On the basis of neurophysiological evidence, the existence of specific octopamine receptors in Aplysia has been postulated. In insects, octopamine produces specific biochemical responses such as increased synthesis of cyclic AMP and phosphorylase activation. The present evidence strongly suggests that octopamine may function as a neurotransmitter in lower animals. Although the physiological role of this amine has not been established in mammals, it appears likely that octopamine may function as a cotransmitter together with NE in the peripheral sympathetic nervous system.
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By use of a sensitive and specific enzymatic isotopic method for the determination of tyramine, the small quantities of this amine which are present endogenously in rat tissues, including brain, heart, kidney and salivary gland, have been... more
By use of a sensitive and specific enzymatic isotopic method for the determination of tyramine, the small quantities of this amine which are present endogenously in rat tissues, including brain, heart, kidney and salivary gland, have been quantitated. The levels of tyramine in brain were increased to a similar extent by injecting animals with a monoamine oxidase inhibitor, pargyline, and a dopamine beta-hydroxylase inhibitor, FLA-63; in contrast, pretreatment of animals with alpha-methyl-para-tyrosine, a tyrosine hydroxylase inhibitor, did not lead to an increase in tyramine levels in brain. Pretreatment of rats with 6-hydroxydopamine resulted in a marked diminution in the tyramine content of rat atria and salivary gland. Denervation of the salivary gland decreased the endogenous level of tyramine approximately 50% in denervated glands compared to undenervated glands. These results suggest that tyramine exists at least partly in sympathetic nerves in many tissues.
Research Interests: Endocrinology, Chemistry, Medicine, Brain, Internal Medicine, and 15 morePubmed, Animals, Male, Tyrosine Hydroxylase, Denervation, Rats, Phenylalanine, Time Factors, Tyramine, Sympathetic Nervous System, Monoamine oxidase, Tyrosine, Salivary Glands, Pharmacology and pharmaceutical sciences, and In Vitro Techniques
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Nerve growth factor (NGF) isolated from mouse salivary gland as well as from other sources has striking effects on sympathetic neuronal growth 8. Histochemical studies have shown that there is a marked numerical increase in serotonin-like... more
Nerve growth factor (NGF) isolated from mouse salivary gland as well as from other sources has striking effects on sympathetic neuronal growth 8. Histochemical studies have shown that there is a marked numerical increase in serotonin-like fluorescent cells in several tissues including the superior cervical ganglia and the iris of neonatal rats, when treated since birth with N G F 1. Although the presence of serotonin in sympathetic ganglia has been suggested by the demonstration in the ganglia of an enzyme that decarboxylates t ryptophan 5, it is known that aromatic amino acid decarboxylase is a relatively non-specific enzyme 1°. Therefore the enzymatic activity could not be considered final proof" for the presence of this indoleamine. In the present study a highly specific gas chromatographic-mass spectrometric assay for serotonin has been used to determine its levels in rat superior cervical ganglia and irises. The biosynthetic enzyme 7 required for its formation was also measured. In experiments performed at the N.I.H., pregnant Sprague-Dawley rats (ZivicMiller, Allison Park, Pa.) were obtained on the lgth day of gestation and kept in individual cages until the litters were born. During the first three days of life the newborn pups were injected subcutaneously daily with 50 #1 saline containing bovine albumin (5/zg/g), N G F (5/zg/g) or 6-hydroxydopamine (50 #g/g) or both N G F and 6-hydroxydopamine. In another series of experiments, neonatal rats at the C.N.R. were injected with 10/zg/g N G F each day. After 4, 9 or 18 days the rats were killed by decapitation and the tissues were frozen immediately on dry ice and sent to the N.I .H. for analysis of serotonin.
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Publisher Summary High concentration of serotonin (5-HT) in the hypothalamus and in the limbic system has been demonstrated by histofluorimetric and biochemical methods. Hypothalamic and limbic 5-HT is present in axon terminals arising... more
Publisher Summary High concentration of serotonin (5-HT) in the hypothalamus and in the limbic system has been demonstrated by histofluorimetric and biochemical methods. Hypothalamic and limbic 5-HT is present in axon terminals arising from the cells that are located in the brain stem raphe nuclei. Electrolytic lesions placed in the dorsal raphe nucleus cause a marked decrease of 5-HT content of the hypothalamus and limbic system as well as the cortical regions. Serotoninergic fibers arising from the dorsal raphe nucleus run through the ventral mesencephalon and enter into the hypothalamus ventral to the medial forebrain bundle. In the hypothalamus, 5-HT fibers inside the medial forebrain bundle can be demonstrated by histofluorescence. Tryptophan hydroxylase activity proved to be high, particularly in the raphe nuclei and in the regions that are rich in 5-HT fibers and terminals; such as the area tegmentalis ventralis, medial forebrain bundle, and nucleus tractus diagonalis. The effects of stressful stimuli on brain serotonin content and metabolism have been studied in the whole brain or in large areas, such as the forebrain or brain stem.
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Octopamine is highly concentrated in neurones of several invertebrate species. Unlike in mammals, octopaminergic neurones in invertebrates are spatially separated from catecholaminergic neurons. In identified nerve cells of Aplysia,... more
Octopamine is highly concentrated in neurones of several invertebrate species. Unlike in mammals, octopaminergic neurones in invertebrates are spatially separated from catecholaminergic neurons. In identified nerve cells of Aplysia, however, this amine coexists with other putative neurotransmitters. Octopamine is synthesized in nerves from tyrosine and tyramine and metabolised mainly by monoamine oxidase. When lobster nerves are depolarized, octopamine is liberated by a Ca2+-dependent process. A specific adenylate cyclase is stimulated by octopamine in several invertebrates to activate phosphorylase in the cockroach, induce a light-flash in firefly lattern or inhibit rhythm contractions in locust muscle. All of these observations provide compelling evidence that octopamine is a neurotransmitter in invertebrates. In mammals octopamine is localised in nerves in peripheral tissues and brain where it seems to coexist with noradrenaline, the catecholamine being present in much higher concentrations. Octopamine is released from nerves together with noradrenaline and it may under certain conditions modify the actions of the adrenergic neurotransmitter. Octopamine is present in unusually high concentrations in certain neurological and hepatic diseases and may have a pathophysiological role.
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Using [3H] diazepam as ligand, it is possible to distinguish neuronal binding sites from those present on glial elements and in peripheral tissues (non-neuronal). The function of the "non-neuronal" binding sites is still... more
Using [3H] diazepam as ligand, it is possible to distinguish neuronal binding sites from those present on glial elements and in peripheral tissues (non-neuronal). The function of the "non-neuronal" binding sites is still obscure. Preliminary data showed a distribution of [3H] diazepam binding sites in kidney that could suggest a localization along the renal tubules. This is the site at which a renal peptide, arginine-vasopressin (AVP) is supposed to act. In an attempt to examine the function of these "non-neuronal" sites, we studied the [3H] diazepam binding in kidney of Brattleboro rats which lack AVP and present the symptoms of diabetes insipidus. The homozygous Brattleboro rats showed an increase in the apparent number of benzodiazepine binding sites (Bmax) compared to Long-Evans control rats. Replacement of AVP in these animals results in a reversal of the electrolyte alterations of diabetes insipidus and in an increase of the affinity of the [3H] diazepam binding. These findings may indicate a possible relationship between benzodiazepine binding sites and vasopressin action in kidney and may support receptor function of these "non-neuronal" binding sites.
Research Interests: Endocrinology, Chemistry, Life Sciences, Medicine, Internal Medicine, and 14 moreKidney, Vasopressin, Animals, Male, Rats, Benzodiazepine, Diazepam, Binding Site, Biochemistry and cell biology, Diabetes Insipidus, Cell Membrane, GABAA receptor, Pharmacology and pharmaceutical sciences, and Arginine Vasopressin
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Research Interests: Endocrinology, Cognitive Science, Chemistry, Medicine, Animal Production, and 15 moreSerotonin, Dopamine, Histamine, Brain, Internal Medicine, Hypothalamus, Female, Animals, Norepinephrine, Clinical Sciences, Rats, Neurosciences, Glutamate decarboxylase, Choline Acetyltransferase, and Paediatrics and reproductive medicine
The use of a sensitive enzymatic assay demonstrates that tryptamine occurs normally in rat brain. Intracisternal administration of [14C]tryptamine results in the formation of N-methyl- and dimethyltryptamine (a psychotomimetic compound)... more
The use of a sensitive enzymatic assay demonstrates that tryptamine occurs normally in rat brain. Intracisternal administration of [14C]tryptamine results in the formation of N-methyl- and dimethyltryptamine (a psychotomimetic compound) in the rat brain. An enzyme that converts tryptamine and N-methyltryptamine to N-methyl- and dimethyltryptamine was found to be present in rat and human brain. The N-methylation of tryptamine was
Research Interests: Chemistry, Science, Medicine, Multidisciplinary, In Vitro, and 7 moreMethylation, Rat Brain, Human Brain, Enzyme, In Vivo, Tryptamine, and Tryptamines
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Drugs which inhibit monoamine oxidase (MAO) in vivo produce changes in the metabolism of over ten amines whic are substrates for this enzyme. Some physiologic and behavioral changes in animals and man occur as direct consequences of these... more
Drugs which inhibit monoamine oxidase (MAO) in vivo produce changes in the metabolism of over ten amines whic are substrates for this enzyme. Some physiologic and behavioral changes in animals and man occur as direct consequences of these amine metabolism alterations, while others occur later and appear related to adaptational responses in amine-containing neurotransmitter systems. Our group has been interested in whether the recently accumlating knowledge about substrate-selective subtypes of monoamine oxidase might have clinical implications. Much of the information regarding MAO substrate selectivity has been obtained in vitro or under conditions of acute MAO-inhibitor administration in rodents, and has indicated that serotonin, norepinephrine and dopamine are preferentially deaminated by MAO type A, while phenylethylamine, phenylethanolamine, tele-methylhistamine, benzylamine and o-tyramine are more avidly deaminated by MAO-B (for reviews see Fowler, et al., 1978; Murphy, 1979). We have been systematically studying the effects of longer-term administration of several selective MAO-inhibitor drugs in animals (Campbell, et al., 1979) and man (Murphy, et al., 1979).
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—A specific and sensitive, radioisotopic microassay for tryptophan hydroxylase (EC 1.14.36) is described, which is capable of determining enzymatic activity in as little as 5 μg of crude brainstem homogenate. 5‐Hydroxytryptophan, the... more
—A specific and sensitive, radioisotopic microassay for tryptophan hydroxylase (EC 1.14.36) is described, which is capable of determining enzymatic activity in as little as 5 μg of crude brainstem homogenate. 5‐Hydroxytryptophan, the immediate product of hydroxylation of tryptophan is enzymatically converted to N‐acetylserotonin. A radioisotopic label is then introduced by the enzymatic methylation of N‐acetylserotonin in the presence of [3H]methyl‐S‐adenosyl‐methionine. The [3H]‐melatonin thus formed is isolated by extraction and counted.With this assay, the activity in individual hypothalamic nuclei (arcuate nucleus, median eminence, suprachiasmatic nucleus, and medial forebrain bundle) has been measured.
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Research Interests: Endocrinology, Neuroscience, Biology, Medicine, Biological Sciences, and 15 moreBrain, Internal Medicine, Animals, Male, Choroid Plexus, Rats, Autoradiography, Receptor, Losartan, Imidazoles, Angiotensin II, Hippocampal formation, Tetrazoles, Medical and Health Sciences, and Angiotensin Receptor Antagonists
Research Interests: Endocrinology, Chemistry, Biology, Medicine, Animal Production, and 15 moreCorticotropin Releasing Hormone, Internal Medicine, Mice, Animals, Male, Gene, Clinical Sciences, Rats, Receptor, Veterinary Sciences, Immobilization, Catecholamines, Gene Expression Regulation, Adrenal Medulla, and Stress Physiological
Quantitative autoradiography using the agonist 125I-Sar1-angiotensin II was used to localize and characterize angiotensin II (AT) receptors in the anterior cerebral artery of the male rat. This artery showed a moderately high number of AT... more
Quantitative autoradiography using the agonist 125I-Sar1-angiotensin II was used to localize and characterize angiotensin II (AT) receptors in the anterior cerebral artery of the male rat. This artery showed a moderately high number of AT receptors, localized throughout the arterial wall. The number of receptors was higher (125 +/- 7 fmol/mg protein) in arteries from young 2-wk-old rats compared with those in adult 8-wk-old rats (43 +/- 2 fmol/mg protein). In the anterior cerebral artery, AT binding was insensitive to displacement with the selective AT1 antagonist DuP 753 but was readily displaced by the selective AT2 antagonist CGP-42112 A (concentration eliciting 50% of maximum inhibition: 6 +/- 1 x 10(-10) M). This indicated that the AT receptors in the cerebral artery were of the AT2 subtype. Our observations suggest that AT may exert its effects on cerebral circulation by stimulation of AT2 receptors and that these receptors may play a role during cerebrovascular development.
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This special Issue presents comprehensive and state-of-the-art advances in supporting the crucial role of the bidirectional interactions between the Brain-Gut Axis in health and diseases with an emphasis on the microbiome-gut-brain axis... more
This special Issue presents comprehensive and state-of-the-art advances in supporting the crucial role of the bidirectional interactions between the Brain-Gut Axis in health and diseases with an emphasis on the microbiome-gut-brain axis and its implications in variety of neurological disorders. There are intimate connections between the brain and the digestive system. Gut microbiota dysbiosis activates the intestinal immune system, enhances intestinal permeability and bacterial translocation, leading to neuroinflammation, epigenetic changes, cerebrovascular alterations, amyloid β formation and α-synuclein protein aggregates. These alterations may participate in the development of hypertension, Alzheimer, Parkinson, stroke, epilepsy and autism. Brainstem nuclei such as the nucleus tractus solitarius (NTS) and the dorsal motor nucleus of the vagus (DMV) regulate gastric motor function by way of bidirectional inputs through the vagus nerve.
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ABSTRACT
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Exposure to stress during early development causes long‐lasting alterations in behaviour and hypothalamic pituitary adrenal (HPA) axis activity, including increased expression of corticotrophin‐releasing hormone (CRH). To determine... more
Exposure to stress during early development causes long‐lasting alterations in behaviour and hypothalamic pituitary adrenal (HPA) axis activity, including increased expression of corticotrophin‐releasing hormone (CRH). To determine whether early‐life stress causes epigenetic changes in the CRH promoter leading to increased CRH transcription, 8‐week old female and male rats, subjected to maternal deprivation (MD) between days 2 and 13 post‐birth, were studied for HPA axis responses to stress and CRH promoter methylation in the hypothalamic paraventricular nucleus (PVN) and central nucleus of the amygdala (CeA). Plasma corticosterone and PVN CRH heteronuclear (hn)RNA responses to acute restraint stress were higher in MD rats of both sexes. DNA methylation analysis of the CRH promoter revealed a significantly lower percentage of methylation in two CpGs preceding (CpG1) and inside (CpG2) the cyclic AMP‐response element (CRE) at −230 bp in the CRH promoter in the PVN but not the CeA of M...
Research Interests: Endocrinology, Neuroendocrinology, Biology, Epigenetics, Medicine, and 15 moreCorticotropin Releasing Hormone, Internal Medicine, Methylation, Female, Animals, Corticosterone, Male, DNA methylation, Clinical Sciences, Rats, Body Weight, Psychological Stress, Neurosciences, Maternal Deprivation, and Adrenal glands
OBJECTIVES/GOALS: Hamsters develop COVID-19 similarly to people because the SARS-CoV-2 spike protein binds with high affinity to hamster ACE2 resulting in host cell entry and replication. Our goal was to establish a hamster model that... more
OBJECTIVES/GOALS: Hamsters develop COVID-19 similarly to people because the SARS-CoV-2 spike protein binds with high affinity to hamster ACE2 resulting in host cell entry and replication. Our goal was to establish a hamster model that mirrors the lung and brain pathophysiology observed in COVID-19. METHODS/STUDY POPULATION: Hamsters infected with SARS CoV-2 are sacrificed on day 1 and day 6 postinfection. Lung histopathology scoring model was implemented for assessment all pathological relevant changes in the lungs of infected animals on tissue sections stained with hematoxylin and eosin. To quantify the extent and severity of lung pathology, two scoring systems were used: the first evaluated all relevant changes in the lungs of the infected animals and the second evaluated only the pathology associated with the pulmonary vasculature. Percentage of airway affected, airway severity, bronchiolar epithelial hyperplasia, alveoli affected, alveolar severity, type II pneumocyte hyperplasi...
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OBJECTIVES/GOALS: The SARS-CoV-2 (Severe Acute Respiratory Syndrome CoronaVirus-2), which underlies the current COVID-19 pandemic, among other tissues, also targets the central nervous system (CNS). The goal of this study is to... more
OBJECTIVES/GOALS: The SARS-CoV-2 (Severe Acute Respiratory Syndrome CoronaVirus-2), which underlies the current COVID-19 pandemic, among other tissues, also targets the central nervous system (CNS). The goal of this study is to investigate mechanisms of neuroinflammation in Lipopolysaccharides (LPS)-treated mouse model and SARS-CoV-2-infected hamsters. METHODS/STUDY POPULATION: In this research I will assay vascular reactivity of cerebral vessels to assess vascular dysfunction within the microcirculation. I will determine expression of proinflammatory cytokines, coagulation factors and AT1 receptors (AT1R) in isolated microvessels from the circle of Willis to assess inflammation, thrombosis and RAS activity in the microvasculature. LPS and SARS-CoV-2, are both associated with coagulopathies and because of that I will measure concentration of PAI-1, von Willebrand Factor, thrombin and D-dimer to assess the thrombotic pathway in the circulation. Histology and immunohistochemistry will...
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Steady state levels of catecholamines (dopamine, norepinephrine, and epinephrine) were measured by the use of radioenzymatic techniques in discrete areas of the kidney (outer and inner cortex, outer and inner medulla) dissected by a... more
Steady state levels of catecholamines (dopamine, norepinephrine, and epinephrine) were measured by the use of radioenzymatic techniques in discrete areas of the kidney (outer and inner cortex, outer and inner medulla) dissected by a "punch" technique from frozen kidney sections of salt-sensitive (DS) and salt-resistant (DR) Dahl rats fed a low or high salt diet. All three catecholamines were present in all areas of the kidney examined. There were gradients of concentrations of each catecholamine in different kidney areas. Renal medullary areas contained proportionally more dopamine than cortical areas. The proportion of epinephrine with respect to the total catecholamine content was relatively high in the inner medulla. Genetic factors and the amount of dietary salt influenced the catecholamine content in specific kidney areas, and these changes were different according to the area considered. DS rats when fed a high salt diet presented increased systolic blood pressure bu...
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We report a quantitative radioimmunohistochemical method, using [125I]-protein A in combination with a specific antibody to methionine enkephalin (Met-enk), for determination of the content of this peptide in discrete areas of rat brain.... more
We report a quantitative radioimmunohistochemical method, using [125I]-protein A in combination with a specific antibody to methionine enkephalin (Met-enk), for determination of the content of this peptide in discrete areas of rat brain. After paraformaldehyde fixation, rat brain sections were incubated with a Met-enk polyclonal antibody, followed by incubation with [125I]-protein A. After autoradiography with 3H-sensitive Ultrofilm, optical densities (OD) were quantified by computerized microdensitometry. The OD obtained were compared to a standard curve, constructed after determination by radioimmunoassay of the Met-enk content in corresponding brain areas from adjacent tissue sections. After comparing 15 different brain areas over a ninetyfold range of concentrations, we found a linear relationship between the content of Met-enk, as determined by radioimmunoassay, and the OD generated by autoradiography. The content of Met-enk in other discrete brain areas can be quantified by in...
Research Interests: Chemistry, Immunohistochemistry, Medicine, Autonomic Nervous System, Caudate Nucleus, and 15 moreCerebral Cortex, Beta decay, Animals, Male, Antigen Presentation, Central Nervous System, Globus Pallidus, Polyclonal Antibodies, Autoradiography, Amino Acid Profile, Brain Chemistry, Putamen, Preoptic Area, Optical Density, and Medical and Health Sciences
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Angiotensin II AT1 receptors are highly localized in the dorsomedial arcuate nucleus. AT1 receptor number is very low during proestrus and in ovariectomized and male rats, and is high only during the estrus phase of the estrous cycle and... more
Angiotensin II AT1 receptors are highly localized in the dorsomedial arcuate nucleus. AT1 receptor number is very low during proestrus and in ovariectomized and male rats, and is high only during the estrus phase of the estrous cycle and after ovariectomized rats receive a sequential estrogen-progesterone treatment. Our results suggest that the mechanism of the estrogen-progesterone inhibition of the prolactin surge may involve the selective stimulation of dorsomedial arcuate AT1 receptors.
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Melatonin-binding sites were studied by quantitative autoradiography in brain and caudal (tail) arteries and in selected brain areas of cycling female rats, ovariectomized rats, and ovariectomized rats treated with estradiol. In the... more
Melatonin-binding sites were studied by quantitative autoradiography in brain and caudal (tail) arteries and in selected brain areas of cycling female rats, ovariectomized rats, and ovariectomized rats treated with estradiol. In the caudal artery, the number of melatonin-binding sites was significantly lower during proestrus, estrus, and metestrus than during diestrus. In ovariectomized rats, melatonin binding to the caudal artery was similar to that found during proestrus, estrus, and metestrus, and a further decrease in the receptor number was produced by estradiol replacement. Similarly, melatonin binding in anterior cerebral arteries was higher during diestrus than at other stages of the estrous cycle. In ovariectomized rats, estradiol replacement also resulted in decreased melatonin binding in anterior cerebral arteries. Conversely, no changes in the number of melatonin-binding sites were observed in the suprachiasmatic nucleus or the area postrema during the estrous cycle, in ovariectomized rats, or after estradiol replacement. The present results suggest that in the female rat, reproductive hormones modulate the expression of cerebral and caudal arterial melatonin-binding sites.
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To evaluate the effects of estrogen on the rat pituitary insulin-like growth factor (IGF) system, binding of [125I]IGF-I and in situ hybridization for IGF-I, the IGF-I receptor and IGF binding protein-2 (IGFBP-2) were coupled with... more
To evaluate the effects of estrogen on the rat pituitary insulin-like growth factor (IGF) system, binding of [125I]IGF-I and in situ hybridization for IGF-I, the IGF-I receptor and IGF binding protein-2 (IGFBP-2) were coupled with quantitative autoradiography. The groups included intact cycling females, intact males, and gonadectomized males and females with or without estrogen pellet implants. Binding of [125I]IGF-I in the anterior lobe of the pituitary occurred in dense clusters over a diffuse lower density background. [125I]IGF-I binding was significantly increased in the estrogen-treated groups and was highest at proestrus compared to the rest of the estrous cycle. IGF-I receptor messenger RNA (mRNA) was distributed diffusely through the anterior pituitary and was not different between the respective gonadectomized and estrogen-treated groups. IGFBP-2 mRNA was clustered throughout the anterior pituitary and was significantly higher in the estrogen-treated groups as noted above for [125I]IGF-I binding. IGF-I mRNA was diffuse throughout the anterior pituitary and was also significantly higher in the estrogen-treated groups. In the neural lobe, [125I]IGF-I binding, IGFBP-2 mRNA, IGF-I receptor mRNA, and IGF-I mRNA were all uniformly distributed and did not differ between groups. The results show that circulating estrogen differentially regulates components of the pituitary IGF-I system in a region-specific manner and suggest that a portion of IGF binding in the anterior pituitary may be to IGFBP-2.
Research Interests: Endocrinology, Biology, Medicine, Gene expression, In Situ Hybridization, and 15 moreEstrogen Receptor, Biological Sciences, Internal Medicine, Female, Animals, Estrogen, Male, Rats, Autoradiography, Estradiol, Anterior Pituitary, Insulin Like Growth Factor, Ovariectomy, orchiectomy, and Medical and Health Sciences
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Recently two subtypes of angiotensin receptors have been described, AT1 and AT2. Currently used radiolabeled agonists and antagonists are not able to discriminate between these receptors subtypes. Here we characterize the use of [125I]... more
Recently two subtypes of angiotensin receptors have been described, AT1 and AT2. Currently used radiolabeled agonists and antagonists are not able to discriminate between these receptors subtypes. Here we characterize the use of [125I] CGP 42112A, a novel, specific ligand for AT2 receptors, in a membrane binding assay and in autoradiography of brain sections of 2 week old rats. [125I] CGP 42112A bound with high affinity and autoradiography revealed binding selectively localized to areas known to express the AT2 receptor subtype only. CGP 42112A, angiotensin II, angiotensin III and PD 123177 competed for [125I] CGP 42112A binding, with potencies consistent with high affinity and specific binding to AT2 receptors. Thus [125I] CGP 42112A will be a useful new tool to study AT2 receptors.
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We used quantitative autoradiography to investigate distribution of angiotensin II (ANG II) receptor subtypes during development of the kidney in the rat. In fetal, newborn, and 3-day-old rats, immature glomeruli in the form of comma and... more
We used quantitative autoradiography to investigate distribution of angiotensin II (ANG II) receptor subtypes during development of the kidney in the rat. In fetal, newborn, and 3-day-old rats, immature glomeruli in the form of comma and S-shaped bodies, located in the nephrogenic zone of the renal cortex, expressed only the angiotensin AT2 receptor subtype. Conversely, the juxtamedullary glomeruli, in more advanced developmental stages, expressed only the AT1 subtype. Similarly, maturing and fully developed glomeruli, present in 1-, 2-, and 8-wk-old rats, expressed only AT1 receptors. In the kidney medulla, there was a similar change in ANG II receptor subtype expression, with the AT2 subtype expressed earlier and the AT1 subtype later during development. Our results demonstrate a selective expression of ANG II receptor subtypes during kidney development. We have found glomerular and medullary AT1 receptors only at developmental stages when kidney function has matured. Conversely, AT2 receptors are expressed only in immature structures, suggesting that they may have a role during kidney organogenesis.
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Peripheral and brain angiotensin II AT(1) receptor blockade decreases high blood pressure, stress, and neuronal injury. To clarify the effects of long-term brain Ang II receptor blockade, the AT(1) blocker, candesartan, was orally... more
Peripheral and brain angiotensin II AT(1) receptor blockade decreases high blood pressure, stress, and neuronal injury. To clarify the effects of long-term brain Ang II receptor blockade, the AT(1) blocker, candesartan, was orally administered to spontaneously hypertensive rats (SHRs) for 40 days, followed by intraventricular injection of 25 ng of Ang II. Before Ang II injection, AT(1) receptor blockade normalized blood pressure and decreased plasma adrenocorticotropic hormone (ACTH) and corticosterone. After central administration of excess Ang II, the reduction of ACTH and corticosterone release induced by AT(1) receptor blockade no longer occurred. Central Ang II administration to vehicle-treated SHRs further increased blood pressure, provoked drinking, increased tyrosine hydroxylase (TH) mRNA expression in the locus coeruleus, and stimulated sympathoadrenal catecholamine release. Pretreatment with the AT(1) receptor antagonist eliminated Ang II-induced increases in blood pressure, water intake, and sympathoadrenal catecholamine release; inhibited peripheral and brain AT(1) receptors; increased AT(2) receptor binding in the locus coeruleus, inferior olive, and adrenal cortex; and decreased AT(2) receptor binding in the adrenal medulla. Inhibition of brain AT(1) receptors correlated with decreased TH transcription in the locus coeruleus, indicating a decreased central sympathetic drive. This, and the diminished adrenomedullary AT(1) and AT(2) receptor stimulation, result in decreased sympathoadrenomedullary stimulation. Oral administration of AT(1) antagonists can effectively block central actions of Ang II, regulating blood pressure and reaction to stress, and selectively and differentially modulating sympathoadrenal response and the hypothalamic-pituitary-adrenal stimulation produced by brain Ang II--effects of potential therapeutic importance.
Research Interests: Endocrinology, Cognitive Science, Drug interactions, Brain, Internal Medicine, and 15 moreHigh Blood Pressure, Blood Pressure, Animals, Corticosterone, Male, Analysis of Variance, Adrenal cortex, Catechols, Locus coeruleus, Adrenocorticotropic Hormone, Inferior Olive, Benzimidazoles, Angiotensin II, Adrenal Medulla, and Adrenal glands
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The high-affinity serotonin 5-HT transporter 5-HTT plays an important role in the removal of extracellular serotonin, thereby modulating and terminating the action of this neurotransmitter at various pre- and post-synaptic serotonergic... more
The high-affinity serotonin 5-HT transporter 5-HTT plays an important role in the removal of extracellular serotonin, thereby modulating and terminating the action of this neurotransmitter at various pre- and post-synaptic serotonergic receptors and heterorecep- tors. In order to characterize the anatomical distribution of the 5-HTT in mouse brain, in situ hybridization histochemistry using 35 w125 x S-labeled riboprobes was performed. These results were compared with 5-HTT binding site distribution as evaluated by I RTI-55 autoradiography. High levels of 5-HTT mRNA were detected in all brain stem raphe nuclei, with variations in labeling among the various subnuclei. Those brain areas known to possess serotonergic cell bodies stained intensely for both 5-HTT mRNA and 5-HTT binding sites. In contrast to previous findings in rat brain, the highest densities of 5-HTT sites were found in areas outside the raphe complex, particularly in the substantia nigra, globus pallidus, and superior...