Enhanced synaptophysin immunoreactivity in rat hippocampal culture by 5-HT1A agonist, S100b, and corticosteroid receptor agonists (original) (raw)
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Brain Research, 1996
The effects of corticosteroid receptor agonists on the expression of 5-HT1A receptor mRNA were measured in rat hippocampal cultures using in situ hybridization histochemistry. In our normal culture system, grown in serum and steroid-free media, moderate to heavy signal for 5-HTIA mRNA transcripts were detected in hippocampal neurons and glial cells. Aldosterone, a type I corticosteroid receptor agonist (10 -9 M), significantly reduced the expression of 5-HTIA mRNA both in neurons and glial fibrillary acidic protein (GFAP)-immunoreactive (IR) cells. The type II corticosteroid receptor agonist, Ru28362 (10 -8 M), also significantly decreased neuronal 5-HTIA mRNA expression. However, it was not as effective as aldosterone in reducing the label over GFAP-IR cells. These data indicate that corticosteroids may directly regulate the expression of hippocampal 5-HT~A receptors at the mRNA level in cultured hippocampal cells.
Brain Research, 1995
Serotonin and dexamethasone act as differentiating agents during development. Reducing circulating adrenal steroids or central 5-HT levels via adrenalectomy (ADX) or the tryptophan hydroxylase inhibitor, para-chlorophenylalanine (PCPA), respectively, has been shown to have de-differentiating effects in the adult brain. Morphometric analysis of 5-HT, S100/3, MAP-2 and synaptophysin immunoreactivity (IR) was used to follow the molecular plasticity of several brain regions after lesioning of 5-HT nerve terminals by para-chloroamphetamine (PCA; 2 × 10 mg/kg s.c.), a serotonin neurotoxin. Two weeks after PCA treatment we observed reductions of 5-HT, S100fl, and MAP-2 IR in parietal and temporal cortex, temporal pole, hippocampus and hypothalamus. The reductions in MAP-2 and synaptophysin-IR were reversed by 3 days of treatment with dexamethasone (10 mg/l drinking water) or ipsapirone, a 5-HTIA agonist (1 mg/kg s.c.). The loss of S100-IR was reversed only by the 5-HT1A agonist. These results indicate that both dexamethasone and serotonin have effects on adult neuronal plasticity but may work via different mechanisms. The implications of these findings to the loss of synaptophysin and MAP-2 staining in Alzheimer's disease are discussed.
Corticosteroids regulate 5-HT1A but not 5-HT1B receptor mRNA in rat hippocampus
Molecular Brain Research, 2000
The role of mineralocorticoid and glucocorticoid receptors (MR and GR, respectively) in the regulation of serotonin receptors has not been clearly delineated. There is no consensus regarding the regulation of 5-HT 1A receptors, and corticosteroid regulation of 5-HT 1B mRNA has not been previously studied. We compared the effects of long-term (two week) adrenalectomy (no MR or GR activation) and several hormone replacement protocols designed to stimulate MR selectively (ALDO), MR and GR (HCT), and continuous MR with cyclical GR activation (SHAM adrenalectomy). 5-HT 1A and 5-HT 1B mRNAs were measured by in situ hybridization in hippocampus and raphe nuclei. None of the experimental manipulations altered 5-HT 1B mRNA levels in the hippocampus or dorsal raphe, and also had no effect on 5-HT 1A mRNA in dorsal or median raphe. However, 5-HT 1A mRNA levels were regulated in a complex manner in the different subfields of hippocampus. We conclude that both MR and GR play an integrated role in regulating 5-HT 1A mRNA levels in hippocampus while having no effect on 5-HT 1B mRNA levels under these conditions.
Effects of glucocorticoids on 5-HT 1A presynaptic function in the mouse
Psychopharmacology, 1994
8-OH-DPAT, a selective 5-HT1A agonist, produced a hypothermic response in mice at a dosage of 0.5 mg/kg. Administration of corticosterone-21-acetate (0.5, 5 and 50 mg/kg, daily for 3 and 10 days) produced a dose-dependent attenuation of this hypothermic response in mice. When all controls and corticosterone treated mice were retested, 14 days after initial testing, they did not differ in the hypothermic responses induced by 8-OH-DPAT. Mice treated with aldosterone (50 mg/ kg), dexamethasone (50 mg/kg) and the specific type 2 corticosteroid receptor agonist, llb,17b-dihydroxy-21methyl-17a-pregna-l,4,6-trien-20-yn-3-one (RU26988, 30 mg/kg) for 10 days, did not differ from vehicle treated controls in the hypothermic response to 8-OH-DPAT. Mice administered corticosterone-21-acetate (30 mg/kg, daily) for 10 days displayed a motor behavioural syndrome, which was not seen in controls, when injected with 5-hydroxytryptophan (5-HTP, 100 mg/kg) 15 min after the injection of carbidopa (25 mg/kg). This was significantly decreased by pretreatment with the 5-HT1A receptor antagonist 1-(2-methoxyphenyl)-4-(4-phthalimidobutyl)-piperazine (NAN-190 5 mg/kg, 30 min prior to administration of carbidopa). Taken together, this evidence is compatible with a specific corticosterone induced facilitation of 5-HT release due to attenuation of inhibitory 5-HT~A autoreceptor function.
Neuroscience, 2002
AbstractöSynaptophysin, an integral membrane glycoprotein of synaptic vesicles, has been widely used to investigate synaptogenesis in both animal models and human patients. Kindling is an experimental model of complex partial seizures with secondary generalization, and a useful model for studying activation-induced neural growth in adult systems. Many studies using Timm staining have shown that kindling promotes sprouting in the mossy ¢ber pathway of the dentate gyrus. In the present study, we used synaptophysin immunohistochemistry to demonstrate activation-induced neural sprouting in non-mossy ¢ber cortical pathways in the adult rat. We found a signi¢cant kindling-induced increase in synaptophysin immunoreactivity in the stratum radiatum of CA1 and stratum lucidum/radiatum of CA3, the hilus, the inner molecular layer of the dentate gyrus, and layer II/III of the piriform cortex, but no signi¢cant change in layer II/III of the entorhinal cortex, 4 weeks after the last kindling stimulation. We also found that synaptophysin immunoreactivity was lowest in CA3 near the hilus and increased with increasing distance from the hilus, a reverse pattern to that seen with Timm stains in stratum oriens following kindling. Furthermore, synaptophysin immunoreactivity was lowest in dorsal and greatest in ventral sections of both CA3 and dentate gyrus in both kindled and non-kindled animals. This demonstrates that di¡erent populations of sprouting axons are labeled by these two techniques, and suggests that activationinduced sprouting extends well beyond the hippocampal mossy ¢ber system.
Activation of glucocorticoid receptors increases 5-HT< sub> 2A receptor levels
Experimental …, 2009
Major depression is associated with both dysregulation of the hypothalamic pituitary adrenal axis and serotonergic deficiency, not the least of the 5-HT 2A receptor. However, how these phenomena are linked to each other, and whether a low 5-HT 2A receptor level is a state or a trait marker of depression is unknown. In mice with altered glucocorticoid receptor (GR) expression we investigated 5-HT 2A receptor levels by Western blot and 3 H-MDL100907 receptor binding. Serotonin fibre density was analyzed by stereological quantification of serotonin transporter immunopositive fibers. To establish an effect of GR activation on 5-HT 2A levels, mature organotypic hippocampal cultures were exposed to corticosterone with or without GR antagonist mifepristone and mineralocorticoid receptor (MR) antagonist spironolactone. In GR underexpressing mice, hippocampal 5-HT 2A receptor protein levels were decreased (26.3 ± 1.6%, p b 0.05) and frontal 5-HT 2A receptor binding was decreased (20 ± 15%, p b 0.01) as compared to wild-type mice. Conversely, in over-expressing GR mice hippocampal 5-HT 2A receptor protein levels were increased (60.8 ± 4.0%, p = 0.0001) and 5-HT 2A receptor binding was increased in dorsal hippocampus (77 ± 35%, p b 0.05) as compared to wild-type mice. No difference in serotonin fibre density was observed in the GR over-expressing mice, while the GR under-expressing mice showed lower serotonergic innervation in the frontal cortex area. An effect of GR activation on 5-HT 2A receptor levels was further corroborated by the culture studies as longterm exposure of 3 μM corticosterone to organotypic hippocampal cultures increased 5-HT 2A receptor levels (p b 0.05). The corticosterone-induced 5-HT 2A receptor up-regulation was blocked by addition of either spironolactone or mifepristone.
Neuroscience, 2005
These experiments explore the role of 5-HT 1A receptors in the regulation of cell proliferation in the dentate gyrus of the intact and adrenalectomized adult rat. Depleting 5-HT with p-chlorophenylalanine (300 mg/kg initially followed by 100 mg/kg/day) or stimulating 5-HT 1A receptors with 8-OH-DPAT (1 mg/kg or 2 mg/kg, s.c. injections twice daily) for 14 days had no effect on cell proliferation as measured by Ki-67 or BrdU (5-bromo-3-deoxyuridine) immunocytochemistry in the dentate gyrus. However, combined treatment with p-chlorophenylalanine followed by 8-OH-DPAT significantly increased cell proliferation compared with p-chlorophenylalanine alone. Micro-injection of the 5-HT neurotoxin 5,7-dihydroxytryptamine into the fimbria-fornix (3.0 g/side) and the cingulate bundle (1.8 g/side) depleted hippocampal 5-HT locally but did not change cell proliferation 3 weeks after the surgery. However, 8-OH-DPAT (1 mg/kg, twice daily) stimulated cell proliferation in the dentate gyrus of hippocampal 5-HT-depleted rats compared with controls. These results suggest that 5-HT 1A modulates cell proliferation in the hippocampus by a direct post-synaptic effect. Previous studies demonstrate that adrenalectomy increases hippocampal 5-HT 1A receptor expression and binding, and thus we investigated whether the effect of adrenalectomy on cell proliferation and survival was dependent on the activity of the 5-HT 1A receptors. In contrast to the null effect following twice-daily s.c. injection, 8-OH-DPAT (2.0 mg/kg/day) delivered by s.c. osmotic pumps increased proliferation in intact rats. The 5-HT 1A antagonist WAY-100635 (1.5 mg/kg/day also delivered by osmotic pump) by itself did not alter cell proliferation, confirming that reduced serotonin activity does not change proliferation, but blocked the effect of 8-OH-DPAT. However, WAY-100635 could not block the stimulating action of adrenalectomy cell proliferation. 5-HT 1A mRNA expression was not altered in the hippocampus by adrenalectomy. Thus, the effect of adrenalectomy on cell proliferation and survival is not 5-HT 1A dependent, despite the interaction between 5-HT 1A and corticosterone.
Naunyn-schmiedebergs Archives of Pharmacology, 2002
Hippocampal 5-HT1A receptors have been shown to be suppressed by glucocorticoids in a variety of animal studies, however the molecular mechanism and the functional meaning of this effect are still not well understood. The present study was designed to investigate the impact of repeated administration of corticosterone (10 mg/kg s.c. twice daily for 7 days) on the functional consequences of 5-HT1A receptor stimulation measured electrophysiologically in hippocampal slices. Additionally, the effects of corticosterone on 5-HT1A receptor binding and on receptor mRNA levels in the hippocampus were studied. Prolonged, but not acute treatment with corticosterone attenuated (±)-8-hydroxy-2-di-N-propylamino)tetralin hydrobromide (8-OH-DPAT)-induced inhibition of population spikes, and 8-OH-DPAT-induced hyperpolarization in rat CA1 hippocampal neurons. Chronic, but not acute treatment with corticosterone also decreased 5-HT1A receptor binding in the CA1 region (in the ventral part only) and the dentate gyrus. A single dose of corticosterone increased [3H]8-OHDPAT binding in the dentate gyrus and in the CA3 and CA4 hippocampal regions. Only acute, but not prolonged treatment with corticosterone decreased the level of 5-HT1A receptor mRNA in the CA1 region and dentate gyrus of the hippocampus. 5-HT turnover in the hippocampus was not influenced by chronic corticosterone. It is concluded that a chronically elevated level of corticosterone can induce functional desensitization of 5-HT1A receptors in the CA1 area of the hippocampus, although this effect is not always followed consequently by decreases in 5-HT1A receptor synthesis in this or other areas of the hippocampus.
Two peptidergic drugs increase the synaptophysin immunoreactivity in brains of 6-week-old rats
The Histochemical …, 2000
The brain-derived peptidergic drug Cerebrolysin has been found to support the survival of neurones in vitro and in vivo. Positive effects on learning and memory have been demonstrated in various animal models and also in clinical trails. In the present study, the effects of Cerebrolysin and its peptide preparation E021 on the synapse density in the hippocampus, the dentate gyrus and in the entorhinal cortex of 24-month-old rats were investigated. Rats received the drugs or saline for control for 19 consecutive days (2.5 ml/kg per day). Slices of the brains were immunohistochemically stained with anti-synaptophysin, which is a specific marker of presynaptic terminals. Quantification of the synapse density was done by using light microscopy and a computerised image analysing system. Our results clearly showed that the rats benefit from the administration of both drugs, showing an enhancement in the number of synaptophysin-immunostained presynaptic terminals in the entorhinal cortex, the dentate gyrus, and also in the hippocampal subfields CA1, CA2, CA3 stratum lucidum and CA3 stratum radiatum. It can be assumed that these effects are the reason for improved cognitive performances of rats treated with Cerebrolysin and E021.