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Role of ethanolamine phosphate in the hippocampus of rats with acute experimental autoimmune encephalomyelitis. Neurochem Int 2011; 58:22-34. [DOI: 10.1016/j.neuint.2010.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 09/28/2010] [Accepted: 10/14/2010] [Indexed: 11/21/2022]
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Hernández-Pinto AM, Puebla-Jiménez L, Arilla-Ferreiro E. alpha-Tocopherol decreases the somatostatin receptor-effector system and increases the cyclic AMP/cyclic AMP response element binding protein pathway in the rat dentate gyrus. Neuroscience 2009; 162:106-17. [PMID: 19393293 DOI: 10.1016/j.neuroscience.2009.04.047] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Revised: 04/06/2009] [Accepted: 04/19/2009] [Indexed: 02/07/2023]
Abstract
Neuronal survival has been shown to be enhanced by alpha-tocopherol and modulated by cyclic AMP (cAMP). Somatostatin (SST) receptors couple negatively to adenylyl cyclase (AC), thus leading to decreased cAMP levels. Whether alpha-tocopherol can stimulate neuronal survival via regulation of the somatostatinergic system, however, is unknown. The aim of this study was to investigate the effects of alpha-tocopherol on the SST signaling pathway in the rat dentate gyrus. To that end, 15-week-old male Sprague-Dawley rats were treated daily for 1 week with (+)-alpha-tocopherol or vehicle and sacrificed on the day following the last administration. No changes in either SST-like immunoreactivity (SST-LI) content or SST mRNA levels were detected in the dentate gyrus as a result of alpha-tocopherol treatment. A significant decrease in the density of the SST binding sites and an increase in the dissociation constant, however, were detected. The lower SST receptor density in the alpha-tocopherol-treated rats correlated with a significant decrease in the protein levels of the SST receptor subtypes SSTR1-SSTR4, whereas the corresponding mRNA levels were unaltered. G-protein-coupled-receptor kinase 2 expression was decreased by alpha-tocopherol treatment. This vitamin induced a significant increase in both basal and forskolin-stimulated AC activity, as well as a decrease in the inhibitory effect of SST on AC. Whereas the protein levels of AC type V/VI were not modified by alpha-tocopherol administration, ACVIII expression was significantly enhanced, suggesting it might account for the increase in AC activity. In addition, this treatment led to a reduction in Gialpha1-3 protein levels and in Gi functionality. alpha-Tocopherol did not affect the expression of the regulator of G-protein signaling 6/7 (RGS6/7). Finally, alpha-tocopherol induced an increase in the levels of phosphorylated cAMP response element binding protein (p-CREB) and total CREB in the dentate gyrus. Since CREB synthesis and phosphorylation promote the survival of many cells, including neurons, whereas SST inhibits the cAMP-PKA pathway, which is known to be involved in CREB phosphorylation, the alpha-tocopherol-induced reduction of SSTR observed here might possibly contribute, via increased cAMP levels and CREB activity, to the mechanism by which this vitamin promotes the survival of newborn neurons in the dentate gyrus.
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Affiliation(s)
- A M Hernández-Pinto
- Grupo de Neurobioquímica, Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Crta. Madrid-Barcelona Km. 33.6, Universidad de Alcalá de Henares, E-28871 Alcalá de Henares, Madrid, Spain
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Abstract
Somatostatin was first identified chemically in 1973, since when much has been established about its synthesis, storage and release. It has important physiological actions, including a tonic inhibitory effect on growth hormone release from the pituitary. It has other central actions which are not well understood but recent cloning studies have identified at least five different types of cell membrane receptor for somatostatin. The identification of their genes has allowed studies on the distribution of the receptor transcripts in the central nervous system where they show distinct patterns of distribution, although there is evidence to indicate that more than one receptor type can co-exist in a single neuronal cell. Receptor selective radioligands and antibodies are being developed to further probe the exact location of the receptor proteins. This will lead to a better understanding of the functional role of these receptors in the brain and the prospect of determining the role, if any, of somatostatin in CNS disorders and the identification of potentially useful medicines.
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Affiliation(s)
- M Schindler
- MRC Laboratory for Molecular Neuroscience, Department of Neurobiology, Babraham Institute, U.K.
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4
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Nakata A, Saito H, Nishiyama N. Facilitatory role of somatostatin via muscarinic cholinergic system in the generation of long-term potentiation in the rat dentate gyrus in vivo. Brain Res 1996; 723:135-40. [PMID: 8813390 DOI: 10.1016/0006-8993(96)00233-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We investigated whether somatostain modulates the generation of long-term potentiation (LTP) in rat perforant path-dentate gyrus synapse in vivo. When somatostatin was injected intracerebroventricularly (i.c.v.) 20 min prior to the tetanus, the intensity of LTP increased dose dependently. Synaptic potential evoked by a low-frequency test stimulation, however, was not altered by somatostatin. We next tested whether the LTP-augmenting effect of somatostain is mediated by cholinergic activation, because somatostatin was demonstrated to promote acetylcholine release in rat hippocampal slice. Pirenzepine (50 nmol/rat), a muscarinic M1 receptor antagonist, did not affect the tetanus-induced LTP by itself. But when it was co-applicated with the somatostatin (50 ng/rat) 20 min before tetanus, it completely abolished the LTP-augmenting effect of somatostatin. Then we examined the effect of octreotide, a potent agonist specifically binding to somatostatin receptor subtypes 2 and 4, on the generation of LTP. Octreotide (500 ng/rat) also facilitated the intensity of LTP. These results suggest that somatostatin facilitates the generation of perforant path-dentate gyrus granule cell LTP by activating the muscarinic cholinergic receptor and the effect of somatostatin is induced, at least partly, by somatostatin receptor subtypes 2 and 4 in vivo.
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Affiliation(s)
- A Nakata
- Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan
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Dournaud P, Jazat-Poindessous F, Slama A, Lamour Y, Epelbaum J. Correlations between water maze performance and cortical somatostatin mRNA and high-affinity binding sites during ageing in rats. Eur J Neurosci 1996; 8:476-85. [PMID: 8963438 DOI: 10.1111/j.1460-9568.1996.tb01231.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Somatostatin levels and high-affinity (somatostatin-1) binding sites are decreased in post-mortem cortical samples of Alzheimer's disease patients but the relationships between such modifications and the cognitive deficits remain to be established. We investigated these relationships in the ageing rat. Three age groups (3-4, 14-15 and 26-27 months) were tested in a modified version of the Morris water maze. Somatostatin mRNA levels were quantified by in situ hybridization and somatostatin binding sites by radioautography using the selective agonist octreotide (SMS 201995) as a competing drug to evaluate high-affinity (somatostatin-1) and low-affinity (somatostatin-2) binding sites. The number of somatostatin mRNA-containing cells was not modified with age or memory performance in cortical, hippocampal and hypothalamic regions, but somatostatin mRNA densities were significantly decreased with age and with memory performance in the frontal and parietal cortex. In the frontal cortex somatostatin mRNA densities were already decreased in 14- to 15-month-old rats, whereas the decrease was observed only in 26- to 27-month-old rats in the parietal cortex. A decrease in somatostatin-1 binding was observed with memory performance, independently of age, in the basolateral amygdala only, while somatostatin-2 binding sites were not affected. In the frontal and parietal cortex, a significant correlation occurred between the latency to find the invisible platform in the water maze and somatostatin mRNA (r = -0.54 and 0.59 respectively, P < 0.02). These results indicate that ageing rats with memory impairments display some of the features of the somatostatinergic deficits observed in Alzheimer's disease.
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Affiliation(s)
- P Dournaud
- U. 159 INSERM, Centre Paul Broca, Paris, France
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Puebla L, Arilla E. Glycine increases the number of somatostatin receptors and somatostatin-mediated inhibition of the adenylate cyclase system in the rat hippocampus. J Neurosci Res 1996; 43:346-54. [PMID: 8714523 DOI: 10.1002/(sici)1097-4547(19960201)43:3<346::aid-jnr9>3.0.co;2-j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The glycine and somatostatin (SS) neurotransmission systems in the brain have been implicated in the function of sensory, motor, and nociceptive pathways. To investigate a possible relationship between these two components, we studied the influence of glycine on the binding of 125I-Tyr11-SS to its receptors and on SS-like immunoreactivity (SSLI) levels in the rat hippocampus and frontoparietal cortex. An intracerebroventricular (i.c.v.) dose of 16 or 160 nmol of glycine induced an increase in the total number of specific SS receptors in the hippocampus but not in the frontoparietal cortex at 15 min following injection, with no changes in the affinity constant. This effect seems to be mediated by inhibitory strychnine-sensitive glycine receptors since pretreatment with the antagonist strychnine (80 micrograms/100 g body weight, intravenously) abolished this response. No significant changes in SSLI content were detected in either brain region of glycine- and strychnine plus glycine-treated rats as compared to control values. Since SS receptors are coupled via guanine nucleotide-binding G proteins to the adenylyl cyclase (AC) system, we also examined the inhibitory effects of SS and the guanine nucleotide Gpp(NH)p on AC activity in hippocampal membranes of control, glycine- and strychnine plus glycine-treated rats since the increase in SS receptors was observed only in this brain area. No significant differences were observed for the forskolin (FK)-stimulated AC enzyme activities in hippocampal membranes from all the experimental groups studied. In the hippocampus of the glycine- (160 nmol) treated group, however, basal AC activity was significantly lower, and the capacity of SS to inhibit FK-stimulated AC activity was increased as compared to the control group. Pretreatment with strychnine prevented the increase in SS-mediated inhibition of AC activity. The functional activity of the inhibitory guanine nucleotide-binding protein Gi, as determined by the inhibitory effect of the stable GTP analogue Gpp(NH)p on FK-stimulated AC activity, was significantly higher in hippocampal membranes of glycine- (160 nmol) treated rats as compared to controls. This suggests that the increased inhibition of AC activity by SS in the glycine-treated group may be due to the increase in Gi activity and/or the increase in the number of SS receptors observed. Alternatively, the greater Gi activity may be responsible for the increased binding of 125I-Tyr11-SS to its receptors observed after glycine administration. Altogether, these data suggest that the hippocampal somatostatinergic system can be regulated by strychnine-sensitive glycine receptors in the rat.
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Affiliation(s)
- L Puebla
- Departamento de Bioquímica y Biología Molecular, Universidad de Alcalá, Madrid, Spain
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López-Sañudo S, Arilla E. Changes in alpha 1-adrenergic neurotransmission alter the number of somatostatin receptors in the rat hippocampus. Neurosci Lett 1994; 177:107-10. [PMID: 7529902 DOI: 10.1016/0304-3940(94)90056-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The administration of an i.p. dose of phenylephrine (2 mg/kg) increased the number of [125I]Tyr11-somatostatin ([125I]Tyr11-SS) receptors and decreased their apparent affinity in rat hippocampal membranes 7 h after its injection. Prazosin (20 mg/kg, i.p.) administered 1 h before phenylephrine reversed effects of the latter on SS binding. Prazosin alone decreased the number of SS receptors without changing the affinity. The addition of phenylephrine or prazosin (10(-5) M) to the incubation medium did not change the SS binding characteristics. The present results support the notion that the alpha 1-adrenergic system regulates the binding of SS to its specific receptors in rat hippocampus.
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Affiliation(s)
- S López-Sañudo
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
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López-Sañudo S, Arilla E. Beta-adrenergic regulation of the somatostatinergic system in rat hippocampus. Neurosci Lett 1994; 165:27-32. [PMID: 7912420 DOI: 10.1016/0304-3940(94)90701-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Interaction of beta-adrenergic and somatostatinergic systems in the hippocampus has not been investigated fully. We studied the influence of DL-isoproterenol (ISO), a beta-adrenergic agonist and DL-propranolol (PRO), a beta-adrenergic blocking agent, on the somatostatinergic system in the rat hippocampus. The short-(5h) and long-term (14 days) administration of ISO (5 mg/kg i.p.) or of PRO (10 mg/kg i.p.) did not affect somatostatin-like immunoreactivity (SSLI) content in the hippocampus of male Wistar rats. Both short- and long-term ISO administration decreased the number of specific [125I]Tyr11-somatostatin ([125I]Tyr11-SS) receptors in synaptosomes from hippocampus (29%, P < 0.05 and 34%, P < 0.05, after short- and long-term administration, respectively) without changing the affinity constant. This decrease in the number of [125I]Tyr11-SS receptors was not due to a direct effect of ISO on these receptors since no decrease in binding was produced by high concentrations of ISO (10(-5) M) when added in vitro. In addition, this decrease could be blocked by pretreatment with PRO. Short- and long-term administration of PRO alone increased the [125I]Tyr11-SS binding in hippocampus (42%, P < 0.05 and 33%, P < 0.05, after short- or long-term administration, respectively) without changing the affinity constant. Although there is no direct evidence that the regulation of SS receptors by the beta-adrenergic system has a physiological significance, this mechanism may provide a means by which the brain environment could modulate SS receptor number and, therefore, sensitivity to SS in a subset of SS-sensitive neurons.
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Affiliation(s)
- S López-Sañudo
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
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Takazawa A, Abraham WC, Sekino Y. Cysteamine potentiates entorhinal activation of dentate gyrus granule cells in rats. Brain Res Bull 1994; 33:437-43. [PMID: 7907266 DOI: 10.1016/0361-9230(94)90287-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A dense plexus of somatostatin-positive fibers and varicosities is observed in the outer two-thirds of the dentate gyrus molecular layer where the glutamatergic perforant path afferents from the entorhinal cortex terminate. To test for a functional interaction between these two pathways, we examined the effects of cysteamine, which enhances somatostatin release for a few hours after administration but produces subsequent depletion of somatostatin lasting several days, on perforant path evoked potentials recorded in the dentate gyrus. Cysteamine (50-400 mg/kg, IP) increased the population spike dose-dependently both in anesthetized and in awake rats, but the slope of the population excitatory postsynaptic potential (EPSP) was left unchanged or even decreased. The antidromic population spike evoked by mossy fiber stimulation was not changed by cysteamine. The change is thought to be due to the increase in slope of the EPSP-spike relationship. In the hippocampal slice preparation, a similar effect of the drug (1-5 mM) on dentate evoked potentials was observed, suggesting that cysteamine acts through its effects on somatostatin in the hippocampus itself. In chronically implanted awake animals, the perforant path population spike was increased 1 h after cysteamine but returned to the predrug level by 24 h when somatostatin seemed to be depleted. These results suggest that hippocampal somatostatin released by cysteamine potentiates the response of dentate granule cells to perforant path input, without directly affecting synaptic transmission or general cell excitability.
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Affiliation(s)
- A Takazawa
- Department of Psychiatry, Saitama Medical School, Japan
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Krisch B. Somatostatin binding sites in functional systems of the brain. PROGRESS IN HISTOCHEMISTRY AND CYTOCHEMISTRY 1994; 28:1-40. [PMID: 7524112 DOI: 10.1016/s0079-6336(11)80054-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- B Krisch
- Anatomisches Institut der Christian Albrechts-Universität, Kiel, Germany
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Leroux P, Weissmann D, Pujol JF, Vaudry H. Quantitative autoradiography of somatostatin receptors in the rat limbic system. J Comp Neurol 1993; 331:389-401. [PMID: 8514916 DOI: 10.1002/cne.903310308] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The distribution of somatostatin receptors (SRIF-R) was analyzed in the limbic system of the adult rat by in vitro autoradiography with [125I-Tyr0,DTrp 8]S14 as a radioligand. Precise quantification of the density of binding sites, at 0.2 mm intervals throughout the different areas revealed a marked heterogeneity of labeling in most structures. In particular, SRIF-R were concentrated in the basal (104.4 +/- 3.3 fmol/mg proteins) and basolateral amygdaloid nuclei (94.8 +/- 4.3 fmol/mg proteins), and in the nucleus of the lateral olfactory tract (121.6 +/- 2.4 fmol/mg proteins), whereas moderate densities were detected in the amygdalo-hippocampal nucleus (76.4 +/- 2.8 fmol/mg proteins). The medial (41.3 +/- 1.9 fmol/mg proteins) and the central (24.0 +/- 1.4 fmol/mg proteins) amygdaloid nuclei contained lower SRIF-R concentrations. It appears from these observations, in the light of the anatomical pathways of the amygdala, that intra-amygdalian SRIF-containing neurons project to the amygdalo-hippocampal nucleus, and that SRIF-R in the basolateral complex are the target of afferents from limbic cortical areas. SRIF-R were detected at different levels of the hippocampal formation but their distribution was more restricted than that of SRIF-containing fibers. The maximal density of sites was detected in the ventral and dorsal parts of the subiculum (115.0 +/- 3.4 and 87.0 +/- 2.8 fmol/mg proteins, respectively) and in the parasubiculum (100.1 +/- 5.4 fmol/mg proteins). In Ammon's horn, the stratum oriens and stratum radiatum of the CA1 field were the only sites enriched in SRIF-R (74.1 +/- 2.0 and 74.6 +/- 1.9 fmol/mg proteins, respectively). The apparent lack of receptors in the pyramidal cell layer indicated that, in Ammon's horn, SRIF is involved in intra-hippocampal communication. Low levels of receptors were found in the hippocampal CA2 and CA3 fields. SRIF-R in the dentate gyrus were mainly concentrated in the molecular layer (57.3 +/- 1.2 fmol/mg proteins). A very high density of sites was also observed in the entorhinal cortex (up to 123.1 +/- 1.5 fmol/mg proteins). A clear mismatch between SRIF and SRIF-R was detected in the septum and the habenula. In the profound layers of the cingulum and retrosplenial cortex, a heterogeneous distribution of SRIF-R was observed. High concentrations of sites were detected in the rostral zone of the cingulate cortex (93.4 +/- 2.0 fmol/mg proteins) while the posterior cingulate only exhibited moderate concentrations of sites (66.5 +/- 0.7 fmol/mg proteins).(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- P Leroux
- European Institute for Peptide Research, CNRS URA 650, UA INSERM, University of Rouen, Mont-Saint-Aignan, France
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López-Sañudo S, Arilla E. Desmethylimipramine pretreatment prevents 6-hydroxydopamine induced somatostatin receptor reduction in the rat hippocampus. REGULATORY PEPTIDES 1992; 41:227-36. [PMID: 1438990 DOI: 10.1016/0167-0115(92)90116-c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Several studies have shown anatomical and functional interconnections between catecholaminergic and somatostatinergic systems. To assess whether somatostatin (SS) may act presynaptically on catecholamine neurons, SS receptors were measured using radioligand test-tube binding assays on synaptosomes from hippocampus and frontoparietal cortex--areas that are innervated by catecholaminergic neurons with different densities and that have a high number of SS receptors--from control and 6-hydroxydopamine (6-OHDA)-treated rats. Intracerebroventricular (i.c.v.) injection of the catecholamine neurotoxin 6-OHDA (0.78 mg free base/kg of body weight in saline with 0.1% ascorbic acid) lowered hippocampal and frontoparietal cortical noradrenaline (NA) and dopamine (DA) levels at 1 week following the injection. Pretreatment of rats with desmethylimipramine (DMI) (40 mg/kg, intraperitoneal) prevented the drop in NA levels, but was not effective in attenuating DA depletion in the two brain areas studied. Treatment with 6-OHDA lowered the number of 125I-Tyr11-SS receptors in the hippocampus (130 +/- 19 vs. 266 +/- 16 fmol/mg protein, P < 0.001), whereas in the frontoparietal cortex a non significant 20% reduction in receptor number was found. The dissociation constants of 125I-Tyr11-SS binding to synaptosomes from frontoparietal cortex (0.65 +/- 0.06 vs. 0.60 +/- 0.04, P not significant) and hippocampus (0.44 +/- 0.04 vs. 0.63 +/- 0.14, P not significant) were similar in control and treated groups. Pretreatment with DMI reversed up to 80% of the effect of 6-OHDA on hippocampus SS receptors. DMI alone had no observable effect on the number and affinity of SS receptors. The 6-OHDA and the DMI treatment did not affect SLI levels in the brain areas studied. These results suggest that a portion of the hippocampal SS receptors may be localized presynaptically on the noradrenergic and dopaminergic nerve terminals.
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Affiliation(s)
- S López-Sañudo
- Department of Biochemistry and Molecular Biology, Medical School, University of Alcalá, Alcalá de Henares, Madrid, Spain
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Muñoz-Acedo G, López-Sañudo S, Arilla E. Reduction of somatostatin receptors in rat hippocampus by treatment with 5,7-dihydroxytryptamine. Neurosci Lett 1992; 146:60-4. [PMID: 1361978 DOI: 10.1016/0304-3940(92)90172-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Several lines of evidence suggest that somatostatin (SS) may interact with serotonergic neurons in the central nervous system. To assess whether SS acts presynaptically on serotonin (5-hydroxytryptamine, (5-HT)) neurons, SS receptors were measured in membranes from the hippocampus, a brain region that receives dense serotonergic innervation and has a high number of SS receptors in control and 5,7-dihydroxytryptamine (5,7-DHT)-treated rats, at 1 and 3 weeks after injection. Intracerebroventricular (i.c.v.) injection of the 5-HT-specific neurotoxin 5,7-DHT (11 micrograms (free base) dissolved in 10 microliters of isotonic saline containing 0.01% ascorbic acid) produced a 70% reduction in hippocampal 5-HT content at 3 weeks after injection but not at 1 week. This change was associated with a significant decrease in SS receptor density in rat hippocampus only at 3 weeks following the injection, without influencing the apparent affinity of the receptors at any time. Administration of 5,7-DHT did not affect somatostatin-like immunoreactivity (SSLI) levels at both times studied. These results suggest that some of the hippocampal SS receptors may be localized presynaptically on the serotonergic nerve terminals.
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Affiliation(s)
- G Muñoz-Acedo
- Department of Biochemistry and Molecular Biology, Medical School, University of Alcalá, Madrid, Spain
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14
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Boyano MC, Bodega G, Alvaro I, Arilla E. Somatostatin binding reduced by ammonium acetate in the rat hippocampus can be reversed by treatment with N-carbamyl-L-glutamate plus L-arginine. Synapse 1992; 12:55-61. [PMID: 1357763 DOI: 10.1002/syn.890120107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effects of short-term (90 min), mid-term (5 days), and long-term (15 days) administration of ammonium acetate (5 mmol/Kg day i.p.) on the somatostatinergic neurotransmitter system of the rat hippocampus have been studied. Scatchard analysis of the binding of 125I-Tyr11-somatostatin to hippocampal dissociated cells indicated that administration of ammonium acetate at the times studied were associated with a decrease in the number of somatostatin receptors in this brain area, whereas the affinity of the same receptors remained unchanged. Administration of ammonium acetate did not affect the levels of somatostatin-like immunoreactivity in the hippocampus. Treatment with N-carbamyl-L-glutamate (1 mmol/Kg, i.p.) plus L-arginine (1 mmol/kg), which lead to the conversion of ammonia into urea, prevented the ammonium acetate-induced changes in somatostatin binding in this brain area. N-carbamyl-L-glutamate plus L-arginine alone had no observable effect on the somatostatinergic system. The decrease in the number of somatostatin receptors induced by ammonium acetate might reflect a decreased sensitivity of the target cells to somatostatin, a phenomenon that could contribute to the depressed neuronal excitability induced by ammonia in the rat hippocampus.
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Affiliation(s)
- M C Boyano
- Department of Biochemistry and Molecular Biology, Medical School, University of Alcalá, Madrid, Spain
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Mengod G, Rigo M, Savasta M, Probst A, Palacios JM. Regional distribution of neuropeptide somatostatin gene expression in the human brain. Synapse 1992; 12:62-74. [PMID: 1357764 DOI: 10.1002/syn.890120108] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The regional distribution of mRNA coding for the neuropeptide somatostatin has been studied in the human brain by in situ hybridization histochemistry using 32P-labeled oligonucleotides. We show that somatostatin mRNA-containing neurons are widely distributed in a number of nuclei and grey areas of the human brain, including neocortex, putamen, nucleus caudatus, nucleus accumbens, amygdala, midbrain, medulla oblongata, hippocampal formation, reticular nucleus of the thalamus, and posterior nucleus of the hypothalamus. No significant hybridization signal was observed in the substantia nigra, claustrum, globus pallidus, thalamus, and cerebellum. The topographic localization of neurons containing SOM mRNA in the human brain is in agreement with previous studies using immunocytochemical or radioimmunoassay techniques. These results show that in situ hybridization histochemistry with oligonucleotide probes can be used to map the distribution of neurons expressing SOM mRNA in human postmortem materials.
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Affiliation(s)
- G Mengod
- Department of Neurochemistry, Centro de Investigación y Desarrollo, CSIC, Barcelona, Spain
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16
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Mentlein R, Buchholz C, Krisch B. Somatostatin-binding sites on rat telencephalic astrocytes. Light- and electron-microscopic studies in vitro and in vivo. Cell Tissue Res 1990; 262:431-43. [PMID: 1981859 DOI: 10.1007/bf00305240] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Using a somatostatin-gold conjugate as ligand, high-affinity binding sites for this neuropeptide were demonstrated at three levels: (i) cultured astrocytes from rat cortex, (ii) hippocampal slice cultures, and (iii) frozen tissue sections of rat telencephalon. The conjugate proved as active as the native peptide in competing for the binding sites. Light-microscopic visualization of bound ligand was achieved by silver intensification of the colloidal gold. This method is faster and yields superior resolution compared with autoradiography. Cultured astrocytes from cortex and hippocampus could be labeled by the ligand. At the light- and electron-microscopic level, astrocytes could be double-labeled by the somatostatin-gold conjugate and immunostaining for glial fibrillary acidic protein (GFAP). In hippocampal slice cultures, the conjugate did not penetrate into the neuropil because of a covering glial layer. However, a portion of this completely GFAP-positive covering glia reacted with the somatostatin ligand. In frozen brain sections, apart from delicate punctate structures, two types of labeled glia cells were seen: single stellate astrocytes and perivascular glia cells.
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Affiliation(s)
- R Mentlein
- Anatomisches Institut, Universität Kiel, Federal Republic of Germany
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