Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The study of neurotransmitter receptors aids in the understanding of the normal anatomy, pharmacology, therapeutics and pathophysiology of disease processes involving the basal ganglia. Receptors may be studied in vitro by homogenate binding experiments, enzyme analysis or quantitative autoradiography and in vivo with positron emission tomography. In the substantia nigra (SN), receptors have been identified for somatostatin, neurotensin, substance P, glycine, benzodiazepine and GABA, opiates, dopamine, angiotensin converting enzyme (ACE) and serotonin. The striatum has receptors for dopamine, GABA and benzodiazepines, acetylcholine, opiates, substance P, glutamate and cholecystokinin. GABA and benzodiazepine receptors are also located in the globus pallidus. In Parkinson's disease, striatal dopamine D-2 receptors are elevated in patients that have not received L-DOPA therapy. This supersensitivity is reversed with agonist therapy. Muscarinic binding to cholinergic receptors seems to correlate with dopamine receptors. Delta opiate receptors are increased in the caudate and mu binding is reduced in the striatum. In the SN of patients with Parkinson's disease, there is reduced binding of somatostatin, neurotensin, mu and kappa opiates, benzodiazepine and GABA and glycine. In Huntington's disease, there is reduced binding of GABA and benzodiazepines, dopamine, acetylcholine, glutamate and CCK. There is increased binding of GABA in both the SN and globus pallidus. Glycine binding is increased in the substantia nigra and ACE is reduced.
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PMID:Receptors in the basal ganglia. 282 9

Whilst the neuropathological correlates of Alzheimer type dementia--cortical neurofibrillary tangles and senile plaques--are well defined, the prevalence of these cortical abnormalities in Parkinson's disease and their relation to dementia is unclear. In a series of 46 consecutive cases of clinically and pathologically established Parkinson's disease the prevalence of mild Alzheimer-type pathology (exceeding the normal but not as extensive as in Alzheimer's disease) was increased 2 to 3 fold compared with an age-matched control group, although there was no obvious relation to the presence or severity of dementia. In a subgroup of Parkinsonian cases (both demented and non-demented), examined neurochemically, there were both similarities (decreased choline acetyltransferase, nicotinic and serotonergic S 1 receptor activities) and distinctions (increased muscarinic receptor binding--particularly to the "L" subtype, and normal serotonergic S 2, somatostatin, and D-aspartate binding together with normal levels of an endogenous nicotine binding inhibitor) compared with a group of cases with Alzheimer's disease. Amongst the various pathological and chemical indices examined, only presynaptic cholinergic markers (including the number of Meynert neurons) and S 1 receptor binding were related to dementia in Parkinson's disease. It is suggested that whilst coincidental classical Alzheimer's disease is infrequent in Parkinson's disease (5% in the present series) Alzheimer's disease itself is distinguished from Parkinson's disease by the formation of numerous neocortical neurofibrillary tangles and a reduction in glutamate uptake, serotonergic S 2 receptors and possibly in endogenous nicotine binding inhibitor.
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PMID:Cortical neuropathological and neurochemical substrates of Alzheimer's and Parkinson's diseases. 282 87

In Alzheimer disease (AD), dysfunction in several neuronal systems is associated with alterations in neurotransmitter receptors. Although receptors are important components of normal neural circuitry, their role in the pathophysiology of AD is only beginning to be clarified. For example, despite the consistent loss of presynaptic cholinergic markers in cortex in AD, the pattern of changes in cortical muscarinic cholinergic receptors is unclear, although the density of nicotinic receptors appears to be reduced. In AD, reductions in serotonin, glutamate, and somatostatin receptors also occur in cortex, and an increase in corticotropin-releasing factor (CRF) receptors has been reported. Studies of neurotransmitter receptor alterations in AD are contributing to the characterization of the biology of this disorder and could result in the development of better diagnostic tests and therapeutic agents.
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PMID:Neurotransmitter receptor alterations in Alzheimer disease: a review. 284 Jan

The present study was conducted to evaluate the effects of neonatal treatment of male rats with monosodium-L-glutamate (MSG) on levels of immunoreactive somatostatin (IRS) in specific regions of the gastroenteropancreatic (GEP) system, in discrete hypothalamic areas, and in peripheral blood. In two identical experiments, IRS concentrations measured in the arcuate nucleus and median eminence of adult, MSG-treated rats were significantly reduced in comparison to IRS levels measured in control littermates. Levels of IRS in the preoptic-periventricular nucleus were significantly reduced only in one experiment. In contrast, neonatal MSG treatment resulted in a twofold increase of IRS levels in the pancreas and antral region of the stomach. Peripheral plasma IRS concentrations were significantly elevated in MSG-treated rats only in one experiment. Since MSG-treated rats have a deficiency in growth hormone (GH) secretion, an additional experiment was performed to determine if GH replacement therapy could reverse some or all of the changes in IRS concentrations induced by MSG treatment. With the exception of a further increase in antral IRS levels, replacement with rGH failed to restore IRS levels in other tissues or plasma of MSG rats to levels measured in control rats. These results show that neonatal MSG treatment not only affects IRS levels in the hypothalamus and blood as previously reported, but in parts of the GEP system as well. Further, effects on hypothalamic IRS levels are opposite to those on GEP IRS levels. The significance of these findings may relate to the altered metabolic state of these animals as a consequence of perturbations in the secretion of other hormones from the hypothalamus, anterior pituitary gland, and possibly the GEP system.
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PMID:Alterations in immunoreactive somatostatin levels in hypothalamic and gastroenteropancreatic tissue as a consequence of neonatal treatment with monosodium glutamate. 285 3

The effects in vivo of physiologic increases in insulin and amino acids on myocardial amino acid balance were evaluated in conscious dogs. Arterial and coronary sinus concentrations of amino acids and coronary blood flow were measured during a 30-min basal and a 100-min experimental period employing three protocols: euglycemic insulin clamp (plasma insulin equaled 70 +/- 11 microU/ml, n = 6); euglycemic insulin clamp during amino acid infusion (plasma insulin equaled 89 +/- 12 microU/ml, n = 6); and suppression of insulin with somatostatin during amino acid infusion (plasma insulin equaled 15 +/- 4 microU/ml, n = 6). Basally, only leucine and isoleucine were removed significantly by myocardium (net branched chain amino acid [BCAA] uptake equaled 0.5 +/- 0.2 mumol/min), while glycine, alanine, and glutamine were released. Glutamine demonstrated the highest net myocardial production (1.6 +/- 0.2 mumol/min). No net exchange was seen for valine, phenylalanine, tyrosine, cysteine, methionine, glutamate, asparagine, serine, threonine, taurine, and aspartate. In group I, hyperinsulinemia caused a decline of all plasma amino acids except alanine; alanine balance switched from release to an uptake of 0.6 +/- 0.4 mumol/min (P less than 0.05), while the myocardial balance of other amino acids was unchanged. In group II, amino acid concentrations rose, and were accompanied by a marked rise in myocardial BCAA uptake (0.4 +/- 0.1-2.6 +/- 0.3 mumol/min, P less than 0.001). Uptake of alanine was again stimulated (0.9 +/- 0.3 mumol/min, P less than 0.01), while glutamine production was unchanged (1.3 +/- 0.4 vs. 1.6 +/- 0.3 mumol/min). In group III, there was a 4-5-fold increase in the plasma concentration of the infused amino acids, accompanied by marked stimulation in uptake of only BCAA (6.8 +/- 0.7 mumol/min). Myocardial glutamine production was unchanged (1.9 +/- 0.4-1.3 +/- 0.7 mumol/min). Within the three experimental groups there were highly significant linear correlations between myocardial uptake and arterial concentration of leucine, isoleucine, valine, and total BCAA (r = 0.98, 0.98, 0.92, and 0.97, respectively); P less than 0.001 for each). In vivo, BCAA are the principal amino acids taken up by the myocardium basally and during amino acid infusion. Plasma BCAA concentration and not insulin determines the rate of myocardial BCAA uptake. Insulin stimulates myocardial alanine uptake. Neither insulin nor amino acid infusion alters myocardial glutamine release.
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PMID:Regulation of myocardial amino acid balance in the conscious dog. 285

The effects of somatostatin (SOM) and cholecystokinin octapeptide (CCK-8) on basal and potassium-evoked release of neurotransmitter amino acids were investigated in slices of rat caudate nucleus (CN) and, for comparison, cerebral cortex (CX). Endogenous aspartate (Asp), glutamate (Glu), glycine (Gly), and gamma-aminobutyric acid (GABA) were measured by high performance liquid chromatography. In both CN and CX, potassium (5-55 mM) produced a concentration-dependent increase in the release of Asp, Glu, Gly, and GABA in the presence of extracellular Ca2+. CCK-8 (1 microM) stimulated in CN the basal and K+-evoked release of Gly to 231% and 160% of control, respectively; this effect was blocked by sulpiride (SULP), a dopamine receptor antagonist. In contrast, SOM (1 microM) inhibited the K+-evoked release of Glu in CN by 26%, an effect that was not blocked by SULP. SOM and CCK-8 did not significantly affect the basal or K+ (35 mM)-evoked release of other amino acids in the CN or of any amino acids in CX. The results indicate that: CCK-8 facilitation of Gly release is dependent of Gly release is dependent on dopamine receptor activation, whereas the inhibition by SOM of Glu release is not: and the effects of SOM and CCK-8 are specific with respect to the brain region affected.
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PMID:Somatostatin and CCK-8 modulate release of striatal amino acids: role of dopamine receptors. 287 62

The evidence for deficiencies in neurotransmitters in Alzheimer's disease is reviewed. Major losses occur in the subcortical afferent projection systems based on acetylcholine, noradrenaline and serotonin. Within the cortex, somatostatin containing neurones and the large pyramidal cells, presumed to use glutamate/aspartate as transmitters, are the most severely damaged cells. The anatomical distribution of cell loss is explainable if the primary site of damage lies within the cortex; nerve cells are damaged by virtue of their presence within or their connections to this region. The senile plaque may represent the site of this damage and neurofibrillary tangle formation and accumulation may lead to cell death. In patients with Down's syndrome who live past 40 years, changes in transmitters apparently identical to those in Alzheimer's disease occur. The dementia of Parkinson's disease appears related to damage to cholinergic, noradrenergic and dopaminergic systems and may reflect a failure of these subcortical regions to sufficiently "activate" an otherwise undamaged cortex.
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PMID:Neurotransmitter deficits in Alzheimer's disease and in other dementing disorders. 287 73

In recent years, a number of new molecules, particularly peptides, have been identified as putative neurotransmitters. The basal ganglia, is especially rich in a number of classical transmitter molecules, amino acids and neuropeptides considered to function in neurotransmission. These include: the well-described terminal fields in the striatum which originate from the brain stem and contain the monoamines, dopamine and serotonin; amino acid containing axons projecting from the cortex and thalamus; striatal cholinergic and peptide-positive interneurons; and amino acid and peptide containing projection neurons to the globus pallidus and substantia nigra. Two amino acids, glutamate and aspartate, are considered to provide excitatory input to the striatum while gamma aminobutyric acid is thought to mediate inhibitory output. Neuropeptides which are richly concentrated in the basal ganglia include, enkephalin, dynorphin, substance P, somatostatin, neuropeptide Y and cholincystokinease. Changes in many of these peptide levels have recently been associated with a number of basal ganglia disorders.
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PMID:Neurotransmitters in the human and nonhuman primate basal ganglia. 287 74

While the dentate gyrus is clearly the simplest of the cortical fields that constitute the hippocampal formation, it nonetheless occupies a pivotal position in the flow of information through this region. Though it has been the subject of anatomical study for over a century and its major connections have been known for almost as long, the use of newly developed histochemical and immunohistochemical techniques have demonstrated many new facets of its intrinsic connectivity and afferent innervation. These techniques have established that it is innervated by cholinergic, noradrenergic, serotonergic and dopaminergic fibers. More recent studies have shown that fibers and cell bodies of the dentate gyrus are immunoreactive for variety of neuroactive substances including the excitatory amino acids glutamate and aspartate, the inhibitory transmitter GABA, as well as peptides of many types including the opioid peptides, enkephalin and dynorphin, several forms of somatostatin, neuropeptide Y, cholycystokinin, vasoactive intestinal peptide and substance P. In this review, we will briefly summarize the distribution of each of these putative transmitter systems within the dentate gyrus. The perspective emerges that the plethora of newly identified and chemically specific fiber systems enriches the classical understanding of the organization of this relatively simple cortical structure. Since there is thus far no evidence for the exclusion from the dentate gyrus of any class of transmitter bearing fiber or neuron found in the neocortex, it can be viewed as a relatively simple model system for studying the interactions of specific transmitter systems in a laminated, cortical structure.
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PMID:Transmitter systems in the primate dentate gyrus. 287 75

Neonatal mice, under fasting conditions, are susceptible to the development of lesions in the arcuate nucleus (AN) of the hypothalamus, with high doses of monosodium L-glutamate (MSG). Feeding of nutrients (e.g., sugars and L-amino acids) has been shown to have a protective effect against the development of these lesions. The purpose of these studies was to elucidate the mechanism of this protective effect. Histopathologic examination of lesions of the AN demonstrated that feeding of weaning mice before subcutaneous administration of toxic doses of MSG suppressed the development of these lesions, as compared to fasted controls. Similarly, the number of necrotic cells in the AN of neonates administered toxic doses of MSG subcutaneously was reduced when D-glucose and L-arginine were administered orally. Atropine obliterated the protective effect of D-glucose. Pretreatments consisting of gastric inhibitory polypeptide (GIP) + oral D-glucose had a protective effect of higher potency than GIP alone. Pretreatments with insulin, anorexigenic peptide (pyroGlu-His-Gly), cholecystokinin, glucagon, bombesin, and substance P (in decreasing order of effectiveness) demonstrated a protective effect against the AN lesion in neonates, whereas somatostatin and beta-endorphin had no effect. Results suggest that the protective effect of nutrients may in part be due to the stimulation of peptide hormone release during the postabsorptive phase. It is postulated that the effect of entero-pancreatic hormone, especially insulin, is to enhance the tolerance of AN neurons of neonatal mice to the toxic dose of L-glutamate.
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PMID:Mealing and related hormone release suppress hypothalamic lesions of neonatal mice by L-glutamate. 288 96


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