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

The distribution of substance P-like immunoreactivity within the squid retina and brain was studied by immunofluorescence. Positive immunoreactivity was observed as a single layer of fibres in the retina. The retina was devoid of tyrosine-hydroxylase, serotonin, gamma-aminobutyric acid, cholecystokinin, neuropeptide Y, somatostatin, enkephalin and vasoactive intestinal peptide immunoreactivities. Substance P immunoreactivity was particularly abundant in the optic lobe. The optic lobe had a distinct layer of substance P fibres near the periphery. Immunoreactive cell bodies, fibres and varicosities were additionally present in various areas of the optic lobe. Substance P immunoreactivity in the other ganglia of the brain was restricted to a few scattered fibres.
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PMID:Substance P-like immunoreactivity in the retina and optic lobe of the squid. 353 37

Pituitary growth hormone (GH) secretion is regulated by two hypothalamic factors: somatostatin, a characterized tetradecapeptide, which inhibits secretion, and GH-releasing factor, unidentified, which stimulates secretion. Biogenic amines, including norepinephrine, dopamine, serotonin, acetylcholine, and gamma-aminobutyric acid have excitatory or inhibitory effects at brain sites to modulate hypothalamic control. alpha-Adrenergic mechanisms have been shown to be of particular importance in the regulation of physiologic GH secretion, which is characterized by episodic surges of release.
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PMID:Functions of central nervous system neurotransmitters in regulation of growth hormone secretion. 610 74

Both Alzheimer's disease and senile dementia of the Alzheimer type (AD/SDAT) are progressive dementias characterized neuropathologically by the presence in the cerebral cortex of numerous neurofibrillary tangles and neuritic plaques. We use the abbreviation AD/SDAT to denote all such cases, irrespective of age of onset. Studies of neurotransmitter-related parameters in autopsied brain tissues from patients with AD/SDAT have, to date, been confined to five putative transmitter systems. Acetycholine-releasing neurones seem to be most markedly and consistently affected, as judged by the extensive reductions in choline acetyltransferase (ChAT) and acetylcholinesterase activities that have been reported. Despite numerous studies, there is no consistent evidence for the involvement of neurones releasing dopamine, noradrenaline, serotonin, or gamma-aminobutyric acid in AD/SDAT, nor for loss of muscarinic cholinergic receptors. Thus, the involvement of cholinergic neurones in AD/SDAT seems to be specific. However, the possible involvement of neurones using other chemicals as transmitters has yet to be explored. The recent recognition of the existence of so-called 'peptidergic neurones' in the mammalian brain (for review see ref. 8) and the availability of radioimmunoassay (RIA) techniques for studying these peptides, have led us to begin a systematic investigation of neuropeptides in autopsied brain tissue from cases of AD/SDAT, and from neurologically normal individuals. We report here results obtained with a RIA for somatostatin, showing that somatostatin-like immunoreactivity in the cerebral cortex is reduced in tissue from AD/SDAT patients.
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PMID:Reduced somatostatin-like immunoreactivity in cerebral cortex from cases of Alzheimer disease and Alzheimer senile dementa. 610 62

Primary cultures of dispersed hypothalamic cells were prepared from embryonic rats to study the release of immunoreactive somatostatin. The immunoreactive somatostatin content of these cultures increased during the first 2 weeks after plating and was readily measurable for several weeks thereafter; this material was characterized by gel permeation and reverse-phase chromatography. Depolarization of the cells with 60 mM K+ or with veratridine resulted in a calcium-dependent release of immunoreactive somatostatin which cochromatographed with synthetic somatostatin on reverse-phase chromatography. Tetrodotoxin blocked the veratridine-evoked release. However, even in the absence of exogenous stimuli, immunoreactive somatostatin was released by the cells into the medium. More than 70% of this tonic release was found to be calcium dependent and to be inhibited by tetrodotoxin, indicating that spontaneous electrical activity in the cultures leads to a release of immunoreactive somatostatin. gamma-Aminobutyric acid inhibited the tonic release of immunoreactive somatostatin and this was reversed by bicuculline. These findings support the hypothesis that gamma-aminobutyric acid inhibits somatostatin release in vivo.
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PMID:Release of immunoreactive somatostatin from hypothalamic cells in culture: inhibition by gamma-aminobutyric acid. 610 13

This study examines the effect of muscimol, a high affinity, specific gamma-aminobutyric acid (GABA) agonist, on glucose-stimulated somatostatin and insulin release from the isolated, perfused rat pancreas. Perfusion with low glucose (50 mg/dl) conditions resulted in basal somatostatin release of 46 +/- 4 pg/ml. Basal insulin release was less than 20 microU/ml. High glucose (300 mg/dl) conditions stimulated somatostatin and insulin release. Steady-state levels of somatostatin and insulin release under high glucose conditions were 425 +/- 12 pg/ml and 419 +/- 18 microU/ml, respectively. Perfusion with medium containing 1 microM muscimol inhibited glucose-stimulated somatostatin release by 38%, whereas the course of glucose-stimulated insulin release was unaffected. Tentative conclusions from this study are (1) that GABA is potentially a modulator of islet somatostatin but not insulin release, and (2) the fact that somatostatin, an inhibitor of insulin, can be suppressed 38% without coincidental increase in insulin release seems to indicate that, under high glucose conditions, somatostatin is without a significant paracrine effect on the beta-cells.
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PMID:Effect of muscimol on glucose-stimulated somatostatin and insulin release from the isolated, perfused rat pancreas. 611 May 97

Mouse cerebral cortex slices will synthesize [3H]glycogen in vitro. Vasoactive intestinal polypeptide (VIP) stimulates the enzymatic breakdown of this [3H]glycogen. The concentration giving 50% of maximum effectiveness (EC50) is 26 nM. Under the same experimental conditions norepinephrine also induces a concentration-dependent [3H]glycogen hydrolysis with an EC50 of 500 nM. The effect of VIP is not mediated by the release of norepinephrine because it is not blocked by the noradrenergic antagonist d-1-propranolol and is still present in mice in which an 85% depletion of norepinephrine was induced by intracisternal 6-hydroxydopamine injections. Other cortical putative neurotransmitters such as gamma-aminobutyric acid, aspartic acid, glutamic acid, somatostatin, and acetylcholine (tested with the agonist carbamylcholine) do not induce a breakdown of [3H]glycogen. This glycogenolytic effect of VIP and norepinephrine, presumed to be mediated by cyclic AMP formation, should result, at the cellular level, in an increased glucose availability for the generation of phosphate-bound energy. Given the narrow radial pattern of arborization of the intracortical VIP neuron and the tangential intracortical trajectory of the noradrenergic fibers, these two systems may function in a complementary fashion: VIP regulating energy metabolism locally, within individual columnar modules, and norepinephrine exerting a more global effect that spans adjacent columns.
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PMID:Vasoactive intestinal polypeptide induces glycogenolysis in mouse cortical slices: a possible regulatory mechanism for the local control of energy metabolism. 611 64

Motilin, [Met]enkephalin, [Leu]enkephalin, somatostatin, taurine, gamma-aminobutyric acid (GABA), and glycine were tested for their effects on Deiters neurons of the lateral vestibular nucleus in rabbits. Iontophoresis was carried out with multibarrelled micropipettes. All four peptides and three amino acids produced depression of neuron firing. No facilitatory responses were observed. The depressant action of each peptide when iontophoresed alone was dose-dependent and was rapid in onset and recovery. Their characteristic actions suggest the possibility of their independent roles as strong inhibitors, although the experimental paradigm does not allow conclusions about the individual potency of each peptide. When GABA was administered together with motilin, [Met]enkephalin, or somatostatin, the effects of the peptide and GABA were additive, producing depression greater than that with application of either substance alone. When GABA was applied in conjunction with [Leu]enkephalin, more complex interactions were observed. At low iontophoretic currents, [Leu]enkephalin antagonized the action of GABA, producing a depression less than that of GABA alone and of considerably slower onset, suggesting an additional modulatory effect. These observations support the conclusion that all substances tested are chemical mediators in the lateral vestibular nucleus and [Leu]enkephalin may be a neuromodulator as well. Because recent immunocytochemical studies indicate that Purkinje cells in the cerebellar cortex are chemically heterogeneous and exhibit immunoreactivity for motilin, taurine, the enkephalins, and somatostatin, as well as for the GABA-synthesizing enzyme glutamic acid decarboxylase, it is suggested that the Purkinje cell projections to vestibular and cerebellar nuclei are multimodal in their chemical coding. The uniformly depressant action of the peptides and amino acids reported here is consistent with earlier observations that Purkinje cells exert an inhibitory influence on the vestibular and central cerebellar nuclei.
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PMID:Inhibitory effects of motilin, somatostatin, [Leu]enkephalin, [Met]enkephalin, and taurine on neurons of the lateral vestibular nucleus: interactions with gamma-aminobutyric acid. 612 70

Regulation of somatostatin (SS) secretion was studied in an in vitro system using collagenase-dispersed cells from fetal rat hypothalamus maintained in long term monolayer culture. Cultured cells exhibit a measurable basal secretion of immunoactive SS (SSLI) which can be augmented by carbachol, acetylcholine, or oxotremorine. The EC50 for carbachol is about 1 microM. Atropine, but not hexamethonium, antagonizes the action of cholinergic agonists. Cobalt or tetrodotoxin pretreatment diminishes basal secretion and eliminates the response to carbachol. Serotonin, several serotonin agonists, and gamma-aminobutyric acid (GABA) suppress carbachol-induced secretion. The GABA blockers bicuculline or picrotoxinin reverse the effect of added GABA and by themselves also augment SSLI secretion. Picrotin is inactive. The direct response to either bicuiculline or picrotoxinin is prevented by cobalt or tetrodotoxin treatment. These observations are consistent with the presence of a muscarinic cholinergic receptor which acts by a mechanism depending on an action potential and calcium influx to enhance the release of SSLI from neurosecretory cells. The data also support the conclusion that GABAergic transmission occurs within the cultures to tonically inhibit SSLI secretion. GABAergic, cholinergic, and serotoninergic systems may thus interact at the level of the hypothalamus to modulate SS secretion in vivo and thereby influence anterior pituitary release of GH and TSH.
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PMID:Muscarinic cholinergic stimulation of somatostatin secretion from long term dispersed cell cultures of fetal rat hypothalamus: inhibition by gamma-aminobutyric acid and serotonin. 612 32

The effects of gamma-aminobutyric acid (GABA) on the secretion of insulin, glucagon, and somatostatin were studied in the isolated dog pancreas. Insulin secretion was inhibited in a dose-related fashion for 10 min or more by as little as 1 microM GABA. A prompt but small and transitory rise in somatostatin secretion, lasting only 1 min, occurred at GABA concentrations of 10 and 100 microM, levels that exert inhibitory effects on nervous tissue. Bicuculline, a GABA antagonist, inhibited insulin secretion and did not antagonize GABA-mediated insulin inhibition. The results suggest that GABA in concentrations that are known to exist in islet tissue can influence the secretion of islet hormones.
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PMID:Effects of gamma-aminobutyric acid on insulin, glucagon, and somatostatin release from isolated perfused dog pancreas. 613 11

The light-evoked release of [3H]acetylcholine (ACh) from the rabbit retina in vivo was measured and taken as an index of cholinergic amacrine cell activity. The light-evoked release of [3H]ACh was reduced by locally applied gamma-aminobutyric acid (GABA), muscimol and 3-aminopropanesulphonic acid (3-APS). The concentrations of these drugs which reduced the light-evoked release of [3H]ACh by 50% (EC50) were 900, 0.3 and 5 microM respectively. In contrast, (-)-baclofen (5 mM), but not (+)-baclofen, significantly increased the light-evoked release of [3H]ACh. The GABA antagonist, bicuculline increased the resting release of [3H]ACh but abolished the inhibitory action of muscimol on the light-evoked release of [3H]ACh. Glycine and taurine also reduced the light-evoked release of [3H]ACh from the retina, their EC50 values being 1.5 and 0.3 mM respectively. This action was blocked by strychnine, but not by bicuculline. In contrast to the GABA antagonist, strychnine did not affect the spontaneous resting release of [3H]ACh. Retinal [3H]ACh release was not affected by dopamine, 5-hydroxytryptamine (5-HT) morphine, substance P, somatostatin, cholecystokinin sulphate, thyrotropin releasing hormone, luteinizing hormone releasing hormone or angiotensin. Electroretinographic changes produced by amino acids and GABA agonists involved mainly the b-wave and were not correlated with their effects on ACh release. Thus, GABA increased the b-wave amplitude, 3-APS had no effect, whilst muscimol, taurine and glycine either had no effect, or reduced the b-wave amplitude. No obvious changes in the e.r.g. were produced by baclofen, dopamine, 5-HT, morphine or any of the peptides studied with the exception of somatostatin, which reduced the amplitude of the b-wave. It is concluded that cholinergic amacrine cell activity in the rabbit retina may be affected by inputs from other amacrines using GABA or glycine (taurine) as their transmitters, but probably not by inputs from peptidergic or dopaminergic amacrine cells. Our experiments do not provide evidence on the sites of action of GABA, glycine or taurine but the action of bicuculline on the resting release of ACh implies that the activity of the cholinergic amacrine cells is affected by a tonically active GABAergic input.
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PMID:Effect of gamma-aminobutyric acid agonists, glycine, taurine and neuropeptides on acetylcholine release from the rabbit retina. 613 99


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