Mianserin Treatment Research Articles

The Effect of Mianserin on Lifespan of Caenorhabditis elegan is Abolished by Glucose.

The antidepressant Mianserin has been shown to extend the lifespan of Caenorhabditis elegan (C. elegan), a well-established model organism used in ageing research. The extension of lifespan in C. elegan was shown to be dependent on increased expression of the scaffolding protein (ANK3/unc-44). In contrast, antidepressant use in humans is associated with an increased risk of death. The C. elegan elegan in the laboratory are fed Escherichia coli (E. coli), a diet high in protein and low in carbohydrate, whereas a typical human diet is high in carbohydrates. We hypothesized that dietary carbohydrates might mitigate the lifespan-extension effect of mianserin. To investigate the effect of glucose added to the diet of C. elegan on the lifespan-extension effect of mianserin. Wild-type Bristol N2 and ANK3/unc-44 inactivating mutants were cultured on agar plates containing nematode growth medium and fed E. coli. Treatment groups included (C) control, (M50) 50 μM mianserin, (G) 73 mM glucose, and (M50G) 50 μM mianserin and 73 mM glucose. Lifespan was determined by monitoring the worms until they died. Statistical analysis was performed using the Kaplan-Meier version of the log-rank test. Mianserin treatment resulted in a 12% increase in lifespan (P<0.05) of wild-type Bristol N2 worms but reduced lifespan by 6% in ANK3/unc-44 mutants, consistent with previous research. The addition of glucose to the diet reduced the lifespan of both strains of worms and abolished the lifespan-extension by mianserin. The addition of glucose to the diet of C. elegan abolishes the lifespan-extension effects of mianserin.

Mood, stress and longevity: convergence on ANK3.

Antidepressants have been shown to improve longevity in C. elegans. It is plausible that orthologs of genes involved in mood regulation and stress response are involved in such an effect. We sought to understand the underlying biology. First, we analyzed the transcriptome from worms treated with the antidepressant mianserin, previously identified in a large-scale unbiased drug screen as promoting increased lifespan in worms. We identified the most robust treatment-related changes in gene expression, and identified the corresponding human orthologs. Our analysis uncovered a series of genes and biological pathways that may be at the interface between antidepressant effects and longevity, notably pathways involved in drug metabolism/degradation (nicotine and melatonin). Second, we examined which of these genes overlap with genes which may be involved in depressive symptoms in an aging non-psychiatric human population (n=3577), discovered using a genome-wide association study (GWAS) approach in a design with extremes of distribution of phenotype. Third, we used a convergent functional genomics (CFG) approach to prioritize these genes for relevance to mood disorders and stress. The top gene identified was ANK3. To validate our findings, we conducted genetic and gene-expression studies, in C. elegans and in humans. We studied C. elegans inactivating mutants for ANK3/unc-44, and show that they survive longer than wild-type, particularly in older worms, independently of mianserin treatment. We also show that some ANK3/unc-44 expression is necessary for the effects of mianserin on prolonging lifespan and survival in the face of oxidative stress, particularly in younger worms. Wild-type ANK3/unc-44 increases in expression with age in C. elegans, and is maintained at lower youthful levels by mianserin treatment. These lower levels may be optimal in terms of longevity, offering a favorable balance between sufficient oxidative stress resistance in younger worms and survival effects in older worms. Thus, ANK3/unc-44 may represent an example of antagonistic pleiotropy, in which low-expression level in young animals are beneficial, but the age-associated increase becomes detrimental. Inactivating mutations in ANK3/unc-44 reverse this effect and cause detrimental effects in young animals (sensitivity to oxidative stress) and beneficial effect in old animals (increased survival). In humans, we studied if the most significant single nucleotide polymorphism (SNP) for depressive symptoms in ANK3 from our GWAS has a relationship to lifespan, and show a trend towards longer lifespan in individuals with the risk allele for depressive symptoms in men (odds ratio (OR) 1.41, P=0.031) but not in women (OR 1.08, P=0.33). We also examined whether ANK3, by itself or in a panel with other top CFG-prioritized genes, acts as a blood gene-expression biomarker for biological age, in two independent cohorts, one of live psychiatric patients (n=737), and one of suicide completers from the coroner's office (n=45). We show significantly lower levels of ANK3 expression in chronologically younger individuals than in middle age individuals, with a diminution of that effect in suicide completers, who presumably have been exposed to more severe and acute negative mood and stress. Of note, ANK3 was previously reported to be overexpressed in fibroblasts from patients with Hutchinson-Gilford progeria syndrome, a form of accelerated aging. Taken together, these studies uncover ANK3 and other genes in our dataset as biological links between mood, stress and longevity/aging, that may be biomarkers as well as targets for preventive or therapeutic interventions. Drug repurposing bioinformatics analyses identified the relatively innocuous omega-3 fatty acid DHA (docosahexaenoic acid), piracetam, quercetin, vitamin D and resveratrol as potential longevity promoting compounds, along with a series of existing drugs, such as estrogen-like compounds, antidiabetics and sirolimus/rapamycin. Intriguingly, some of our top candidate genes for mood and stress-modulated longevity were changed in expression in opposite direction in previous studies in the Alzheimer disease. Additionally, a whole series of others were changed in expression in opposite direction in our previous studies on suicide, suggesting the possibility of a "life switch" actively controlled by mood and stress.

Effect of mianserin on gastric sensorimotor function and gastric emptying: a randomized, placebo‐controlled, double‐blind, crossover study in healthy volunteers

Antidepressants such as mianserin can improve symptoms in some functional dyspeptic patients but their mechanism of action remains unclear. We aimed to assess the effects of mianserin on gastric sensorimotor function in man. In this randomized, placebo-controlled, double-blind, crossover study 12 healthy subjects (six men) underwent a gastric barostat study and a gastric emptying breath test after 7 days pretreatment with placebo or mianserin (20 mg; p.o.). Graded isobaric and isovolumetric distentions were performed to determine gastric compliance and sensitivity. Subsequently, intrabag pressure was held constant and the volume increase after administration of a liquid meal (200 mL; 300 kcal) was studied. Breath was sampled before and after ingestion of a test meal and half-emptying times for solids and liquids were determined from the breath samples. Mianserin was compared to placebo using t-tests and mixed model analysis (mean ± SD). Mianserin did not affect pressures or volumes needed to induce first perception or discomfort. During isovolumetric distensions compliance was decreased after mianserin treatment (1.8 ± 0.4 vs 2.0 ± 0.3 mmHg 100 mL(-1); P < 0.05). Premeal volumes were comparable in both treatment arms (221 ± 99 vs 220 ± 88 mL), but meal-induced relaxation during the first 30 min was significantly inhibited after mianserin treatment (F(6,40) = 2.58, P < 0.05). Mianserin did not affect either solid or liquid gastric emptying. Mianserin does not alter gastric emptying rate or sensitivity to gastric distension, but inhibits gastric accommodation to a meal in its early phase. These observations provide no explanation for the effects of mianserin in functional dyspeptic patients.

The role of serotonin in the enhancement of long-term memory resulting from predator detection in Lymnaea

Serotonergic systems play important roles in modulating stress-induced arousal and vigilance behaviours. The pond snail, Lymnaea, shows multiple defensive vigilance behaviours in response to the stress associated with predator detection. Predator detection elicited by crayfish effluent (CE), increases the time to re-emerge from the shell and enhances the shadow withdrawal response. More importantly, in Lymnaea, CE enhances the ability to form long-term memory (LTM). We investigated the role of the serotonergic system in these anti-predator responses in Lymnaea. Using a serotonin-receptor antagonist, mianserin, we found that two defensive vigilance behaviours (e.g. increasing the time to re-emerge from their shell and shadow response) elicited by CE were not observed when the serotonergic system was disrupted. Also, methysergide, another serotonin antagonist, blocked the enhanced LTM formation after training in CE. Importantly, mianserin did not alter LTM formation in pond water (PW). These data suggest that a serotonergic system is activated only when Lymnaea detect a predator. When snails were trained in CE using a training procedure that in PW produces a 24-h LTM, a more persistent form of LTM (5 days) occurred. This more persistent form of LTM was abolished after mianserin treatment. Increasing 5-HT levels in the snail by the injection of 5-HT was also associated with enhanced LTM formation. Lastly, we tested whether the osphradium is implicated in CE detection and subsequent enhanced formation of LTM. Cutting the osphradial nerve to the CNS resulted in the loss of the ability to form enhanced LTM in CE. Together, these findings support the hypothesis that the serotonergic system plays a key role in modulating the predator-induced stress responses in Lymnaea.

Age-dependent plasticity of sex pheromone response in the moth, Agrotis ipsilon: Combined effects of octopamine and juvenile hormone

Male moths use sex pheromones to find their mating partners. In the moth, Agrotis ipsilon, the behavioral response and the neuron sensitivity within the primary olfactory centre, the antennal lobe (AL), to sex pheromone increase with age and juvenile hormone (JH) biosynthesis. By manipulating the JH level, we previously showed that JH controls this age-dependent neuronal plasticity, and that its effects are slow (within 2 days). We hypothesized that the hormonal effect might be indirect, and one neuromodulator candidate, which might serve as a mediator, is octopamine (OA). Here, we studied the effects of OA and an OA receptor antagonist, mianserin, on behavioral and AL neuron responses of mature and immature males during stimulation with sex pheromone. Our results indicate that, although OA injections enhanced the behavioral pheromone response in mature males, OA had no significant effect on behavior in immature males. However, mianserin injections decreased the behavioral response in mature males. AL neuron sensitivity increased after OA treatment in immature males, and decreased after mianserin treatment in mature males. Determination of OA levels in ALs of immature and mature males did not reveal any difference. To study the possible interactive effects of JH and OA, the behavioral pheromone response was analyzed in JH-deprived mature males injected with OA, and in immature males injected with fenoxycarb, a JH agonist, and mianserin. Results show that both JH and OA are necessary to elicit a behavioral response of A. ipsilon males to sex pheromone.

Complaints of Poststroke Insomnia and Its Treatment with Mianserin

We assessed the prevalence and associations of symptoms of insomnia in patients with acute ischemic stroke, and evaluated whether mianserin as a sedative antidepressant is beneficial in the treatment of poststroke insomnia. One hundred consecutively hospitalized patients were randomized to receive 60 mg/day of mianserin (n = 51) or placebo for 1 year in a double-blind trial with a 6-month follow-up after the therapy. Symptoms of insomnia were assessed with the three insomnia-related items of the Hamilton Depression Scale; patients were defined as insomniacs if any of these items was positive. Complaints of insomnia occurred in 68% of patients on admission, and in 49% at 18 months, and they were as frequent in all subgroups of patients. From 2 months, symptoms of insomnia were associated independently with depression. Living alone before stroke (at 0 and 2 months) and age (at 12 months) were other independent predictors of insomnia. The rate of recovery as evaluated by the insomnia score was more rapid in patients on mianserin than in those on placebo. At 2 months, the scores were significantly different favoring mianserin treatment (1.3 vs. 0.8, p = 0.02). We conclude that insomnia is a common complaint after ischemic stroke. Mianserin had a beneficial influence on the recovery from symptoms of insomnia, even though the intensity of poststroke depression was low.

Modulation of cellular expression of glucocorticoid receptor and glucocorticoid response element-DNA binding in rat brain during alcohol drinking and withdrawal.

To define the molecular mechanisms of abnormal hypothalamic pituitary adrenal (HPA) axis during ethanol dependence, we investigated the effect of chronic ethanol treatment (15 days) and its withdrawal (24 h) on the expression of glucocorticoid receptors (GRs) and glucocorticoid response element (GRE)-DNA binding in the rat brain. The effects of chronic mianserin [serotonin (5-HT)(2A/2C) antagonist] treatment on these parameters in various brain structures of control diet-fed and ethanol-fed rats were also investigated. It was found that ethanol treatment and withdrawal significantly decreased the GR protein levels in cortical (cingulate gyrus, frontal, parietal, and piriform cortex) and amygdaloid (central, medial, and basolateral) structures and paraventricular nucleus (PVN) of hypothalamus of rats. It was also observed that ethanol treatment produced significant reductions in GR protein levels in various hippocampal structures (CA1, CA2, CA3, and dentate gyrus), but these changes were normalized during ethanol withdrawal. Ethanol treatment also significantly decreased GRE-DNA binding in rat cortex and hippocampus, which remained decreased in the cortex but reverted to normal in hippocampus during ethanol withdrawal. Chronic mianserin (alone) treatment had no effect on cortical GRE-DNA binding and GR protein levels in cortical, amygdaloid, or PVN structures but significantly decreased the GR protein expression in various hippocampal structures and GRE-DNA binding in whole hippocampus. However, when administered concurrently with ethanol treatment, mianserin significantly antagonized the reductions in cortical GRE-DNA binding and in GR protein expression in cortical, PVN, and central, but not medial and basolateral, amygdaloid structures during ethanol withdrawal. On the other hand, mianserin treatment along with ethanol administration significantly decreased the hippocampal GRE-DNA binding and GR protein expression in various hippocampal structures during ethanol withdrawal. Furthermore, ethanol treatment and its withdrawal or mianserin treatment had no effect on the neuron-specific nuclear protein levels in the various brain structures. Taken together, these results indicate that interaction of 5-HT(2A/2C) receptors with GRs in cortical, central amygdaloid, and PVN structures may play a role in neural mechanisms of alcohol dependence. It is possible that decreased GR expression in PVN may be responsible for the abnormal HPA axis during ethanol exposure and withdrawal.

Effects of voluntary ethanol intake on the expression of Ca(2+) /calmodulin-dependent protein kinase IV and on CREB expression and phosphorylation in the rat nucleus accumbens.

To define the molecular basis of alcohol drinking behaviors, the effects of voluntary ethanol intake on the expression of Ca(2+)/calmodulin-dependent protein kinase IV (CaM kinase IV) and on the expression and phosphorylation of cAMP responsive element binding protein (CREB) [corrected] in the nucleus accumbens (NAc), central amygdala, and frontal cortex of rats were investigated. Voluntary ethanol intake significantly decreased the expression of CaM kinase IV and CREB phosphorylation but not of CREB protein levels [corrected], specifically in the shell of NAc. These changes were not observed in the core of NAc, central amygdala and frontal cortex. Mianserin treatment significantly attenuated ethanol intake and antagonized the voluntary ethanol-induced reduction in expression of CaM kinase IV and CREB phosphorylation in the shell of NAc. This is the first evidence to suggest that decreased CaM kinase IV-dependent CREB phosphorylation in the shell region of NAc may play a role in the reward mechanisms of alcohol drinking.

Dissociable effects of the 5-HT 2 antagonist mianserin on associative learning and performance in the rabbit

Serotonin 5-HT 2 antagonists that significantly retard the acquisition of classically conditioned responses (CRs) also impair the performance of the unconditioned response (UR). Effects on the UR appear to be due to an inverse agonist action at the 5-HT 2 receptor. These findings raised the possibility that the learning deficits were either secondary to a performance deficit and/or that the retardation of learning was not due to actions at the serotonin 5-HT 2 receptor. In this study, we examined the effects of the 5-HT 2-receptor antagonists, namely mianserin and d-2-bromolysergic acid diethylamide hydrogen tartrate (BOL), on CR acquisition. We also determined whether the retarded acquisition of CRs produced by mianserin (a) was due to an action at the 5-HT 2 receptor and (b) was secondary to a performance deficit. Effects of drugs on CR acquisition, maintenance, and retention were determined during trace-conditioning of the rabbit's nictitating membrane (NM) response. BOL (0.058 to 5.8 μmol/kg) had no effect on CR acquisition, whereas mianserin (0.1 to 10 μmol/kg) produced a significant and dose-dependent retardation of CR acquisition. The retarded CR acquisition produced by mianserin (10 μmol/kg) was due to its actions at the 5-HT 2 receptor, because this effect was completely blocked by a dose of BOL (5.8 μmol/kg) that had no effect when given alone. Neither maintenance nor retention of learning was affected by mianserin treatment during acquisition. We conclude that mianserin acts as an inverse agonist at the serotonin 5-HT 2 receptor to produce both a retardation of CR acquisition and an impairment of the UR. However, the learning and performance effects of mianserin are separable.

Abstracts of literature

Abstracts of literature

Post-stroke depression, not to be underestimated

Depression occurs in almost half of stroke survivors, 1 Kotila M Numminen H Waltimo O Kaste M Depression after stroke: results of the FINNSTROKE Study. Stroke. 1998; 2: 368-372 Crossref Scopus (330) Google Scholar yet H Palomäki and colleagues 2 Palomäki H Kaste M Berg A et al. Prevention of poststroke depression: 1 year randomised placebo controlled double blind trial of mianserin with 6 month follow up after therapy. J Neurol Neurosurg Psychiatry. 1999; 66: 490-494 Crossref PubMed Scopus (105) Google Scholar found that the disorder was neither common nor responsive to mianserin treatment in their trial among 100 consecutive patients with ischaemic stroke. They found that, according to DSM-IIIR criteria, major depression was present in 6% at the initial stage, 11% at 1 year, and 18% at 18 months. Mianserin, a tetracylic antidepressant, had no effect on depression or functional outcome as measured by the Rankin scale or the Barthel index. DEPARTMENT OF ERRORCan growth hormone therapy cause diabetes?—In this Correspondence letter by J P Monson and colleagues (May 13, p 1728), the third sentence of the third paragraph should be, “His warnings about the placebo effect of GH replacement (his use of the word tainted is rather curious) on improved wellbeing are overstated, particularly in view of the continued improvement in wellbeing, which is observed between 6 months and 12 months of treatment.5” Also, reference 3 should not be cited in the first paragraph. Full-Text PDF

Prevention of poststroke depression: 1 year randomised placebo controlled double blind trial of mianserin with 6 month follow up after therapy

OBJECTIVES(1) To test whether early prophylactic antidepressive treatment by mianserin is able to prevent poststroke depression, and (2) to discover whether mianserin as an antidepressant has any beneficial influence on...

Effects of nocturnal doses of mirtazapine and mianserin on sleep and on daytime psychomotor and driving performance in young, healthy volunteers

Eighteen healthy volunteers participated in a randomized, double blind, cross-over trial. They received mirtazapine, mianserin or placebo during separate periods of 15 days. Mirtazapine and mianserin were respectively administered in doses of 15 mg and 30 mg nocte for the first 7 days and doses of 30 mg and 60 mg nocte for the remaining 8 days. Assessments were made at baseline and on days 2, 8, 9 and 16 of each period to compare effects of drugs and placebo on mood, psychomotor (CTT, CRT, CFF and Vigilance) and ‘actual’ driving performance. Sleep quality and duration and side-effects were assessed at baseline and every treatment day. Mirtazapine 15 mg and mianserin 30 mg slightly impaired psychomotor and driving performance on day 2 of treatment. On day 8, the effects were virtually gone, although some driving impairment could still be observed in the mianserin condition. No drug effects on performance were found on day 9 despite the dose escalation. On day 16 of treatment, driving performance and vigilance slightly decreased in, respectively, the mirtazapine and the mianserin conditions. These effects indicate that tolerance to the drugs' adverse effects was not complete. This observation was also supported by subjective data. Similar increments in sleep duration and feelings of lethargy, drowsiness and weakness were observed throughout treatment with both drugs. Alertness and contentedness was always lower during both drug treatments than with placebo. Spontaneously reported adverse events were similar to self-rated side-effects and more of both were recorded during mianserin treatment. It is concluded that the acute and subchronic effects of nocturnal doses of both drugs were similar and equally low in magnitude. Effects on performance were much less than those seen in other studies after administration during the day. Full daily doses of both drugs should be prescribed in nocturnal dosing regimens, and not in divided doses over the day, for avoiding excessive sedation and performance impairment. © 1998 John Wiley & Sons, Ltd.

Mianserin-induced down-regulation of human 5-hydroxytryptamine2A and 5-hydroxytryptamine2C receptors stably expressed in the human neuroblastoma cell line SH-SY5Y.

We have assessed the ability of the serotonergic antagonist mianserin to modulate the number and functional activity of human 5-hydroxytryptamine2A (5-HT2A) and 5-HT2C receptors stably expressed in the human neuroblastoma cell line SH-SY5Y. Incubation of cells expressing the 5-HT2A receptor with mianserin (100 nM) for 24 h caused a significant decrease (48%) in the binding capacity of [3H] ketanserin. This receptor down-regulation was associated with a corresponding decrease in the maximal production of inositol phosphates induced by 5-HT but not by carbachol. Exposure of cells expressing the 5-HT2C receptor to mianserin (100 nM) for 72 h but not for 24 h similarly resulted in a significant reduction (44%) in [3H]mesulergine binding. Corresponding analysis of inositol phosphate production by 5-HT at the 5-HT2C receptor after incubation with mianserin showed no change in maximal response after 24 h. No change in the binding capacity of either radioligand was seen after incubation with mianserin for 1 h. A decrease in the binding affinity of both radioligands was also observed after mianserin treatment, but this decrease was similar after 1 h of incubation to that seen after 24 or 72 h, and was probably due to the retention of mianserin within the tissue. We conclude that antagonist down-regulation is evident at human 5-HT2A and 5-HT2C receptors stably expressed in a human neuroblastoma cell line and is probably mediated by a direct action of mianserin at the receptor.

Mianserin, a 5-HT2a/2c and alpha 2 antagonist, in the treatment of sexual dysfunction induced by serotonin reuptake inhibitors.

Sexual dysfunction is commonly encountered in patients treated with antidepressants. The exact mechanism responsible for the sexual impairment is as yet unclear, although activation of the serotonergic system has been implicated. In the present study, we examined the effect of the 5-HT2a/2c and alpha 2 antagonist mianserin in the treatment of patients with sexual dysfunction induced by serotonin reuptake inhibitors (SRIs). Mianserin 15 mg was coadministered to 15 male subjects with new-onset sexual dysfunction who were under treatment with SRIs. Four major domains of sexual activity-desire, erection, orgasm, and satisfaction-were assessed once weekly for 4 weeks. At the end of the study, 9 of the 15 subjects reported a marked improvement in their sexual functioning, 2 reported partial improvement, and only 4 subjects showed no improvement at all. The beneficial effects were prominent in the areas of orgasm and satisfaction and were usually noted within the first and second week of mianserin treatment. The addition of mianserin to the treatment regimen was not associated with either improvement or worsening of the basic psychiatric clinical status. It appears that the coadministration of low-dose mianserin may be an additional option in the treatment of sexual dysfunction induced by SRIs.

Mianserin treatment of patients with psychosis induced by antiparkinsonian drugs.

We evaluated the effects of mianserin, a relatively selective 5-HT2 receptor antagonist, on symptoms related to drug-induced psychosis in patients with Parkinson's disease (PD). A total of 12 patients with PD who had developed drug-induced psychosis showed delirium (DSM-III-R criteria; n = 10) and pure visual hallucinations (n = 2). The antiparkinsonian drugs involved in the drug-induced psychosis were L-DOPA/carbidopa, bromocriptine, trihexyphenidyl, and amantadine. They received mianserin (mean 36.7 mg, range 20-60 mg) given orally for 8 weeks. Complete relief or marked improvement in psychotic symptoms was noted in 8 patients, moderate improvement in 2 patients, and no effect in 2 patients. The parkinsonian disability also decreased slightly in 8 patients. These results suggest that serotonin antagonism at 5-HT2 receptors may not only play an important role in the treatment of drug-induced psychosis in PD, but may also ameliorate the symptoms of parkinsonism.

Effects of 8-OH-DPAT on corticosterone after acute and chronic administration of antidepressants

1. 1. Serotonin has a facilitary role in the role of corticosterone secretion. 8-Hydroxy-2-(di-n-propylamino)tetrali (8-OH-DPAT), a selective 5-HT1A agonist, dose dependency (0.25–1.0 mg/kg i.p.) increased rat plasma corticosterone concentration. 2. 2. 3 days parachlorophenylalanine (PCPA) (150 mg/kg) administration did not effect the 8-OH-DPAT-induced corticosterone secretion. 3. 3. Corticosterone responses to 8-OH-DPAT (0.5 mg/kg) were significantly attenuated by pretreatment with propranolol (5 mg/kg). Ketanserin (2 mg/kg), haloperidol (0.2 mg/kg), prazosin (0.1 mg/kg), and ICS-205930 (30 μ/kg) failed to antagonize the corticosterone response to 8-OH-DPAT. 4. 4. 8-OH-DPAT-induced corticosterone were investigated in male rats after treatment with mianserin (2, 10 mg/kg), imipramine (5 mg/kg), desipramine (5 mg/kg), doxepine (5 mg/kg) for 1 day or 3 weeks. Chronic mianserin (10 mg/kg) and doxepine (5mg/kg) did significantly increase 8-OH-DPAT-induced corticosterone response. Acute antidepressant, chronic imipramine, desipramine and mianserin (2 mg/kg) treatment did not change it. 5. 5. These findings demonstrate that chronic treatment of some antidepressants potentiates 8-OH-DPAT-induced increase in plasma corticosterone, by actions at 5-HT-1A receptors located postsynaptically on 5-HT neurones.

Chromic mianserin or eltoprazine treatment in rats: effects on the elevated plus-maze test and on limbic 5-HT 2C receptor levels

Rats were chronically treated with mianserin (10 mg/kg i.p) or eltoprazine (1 mg/kg i.p.) and were tested in the elevated plus-maze test for anxiety. 5-HT 2C (previously 5-HT 1C, see Humphrey et al., 1993, Trends Pharmacol. Sci. 14, 223) binding sites and their mRNA were evaluated in limbic structures (i.e., amygdala, hippocampus, septum) of a sample of these rats by autoradiographic binding studies and in situ hybridization histochemistry. Mianserin and eltoprazine displayed opposite effects in the elevated plus-maze: mianserin induced anxiolytic-like effects, while eltoprazine showed anxiogenic-like ones. Within the amygdala, but not in other structures, the quantitative autoradiographic analysis of the 5-HT 2C binding sites showed a differential effect: mianserin treatment induced a decrease in the number of these sites, while eltoprazine treatment resulted in an increase. In spite of this, neither mianserin- nor eltoprazine-treated rats displayed an alteration in the 5-HT 2C receptor mRNA levels in the brain regions examined. Our results are suggestive of a relation between anxiolytic/anxiogenic-like effects and the level of 5-HT 2C binding sites in the amygdala.

Effects of chronic mianserin administration on serotonin metabolism and receptors in the 5-hydroxytryptophan depression model

Akiyoshi, Jotaro, Kounosuke Tsuchiyama, Yuuko Mizobe, Makoto Nakamura, Hiromitsu Kuranaga and Haruo Nagayama: Effects of Chronic Administration on Serotonin Metabolism and Receptors in the 5-Hydroxytryptophan Depression Model. Prog. Neuro-Psychopharmacol. & Biol. Psychiat. 1994, 18(1): 165–179. 1. 1. To further investigate a previous postulate that increased serotonergic activity may cause depression, the effects of chronic mianserin administration on 5-HT, its metabolites, and the subtypes of 5-HT receptors were studied. 2. 2. The levels of 5-HT, 5-hydroxyindoleacetic acid, 5-HTP, 5-HT turnover and their response to 5-HTP administration all exhibited no change following mianserin treatment. 3. 3. The B max value of the high affinity site of the 5-HT-1A receptor increased and the B max value of 5-HT-2 receptor decreased with no change in the low affinity site of the 5-HT-1A receptor nor in the 5-HT-1B receptor. 4. 4. The response to 5-HTP administration showed no change in any of these receptors. 5. 5. These results suggest that the chronic mianserin administration might block both the 5-HT-2 and 5-HT-1A receptors in the 5-hydroxytryptophan depression model.

Chronic electroconvulsive seizures increase the expression of serotonin2 receptor mRNA in rat frontal cortex.

The present study examines the influence of electroconvulsive seizure (ECS), as well as antidepressant drugs, on levels of serotonin2 (5-HT2) receptor mRNA in rat frontal cortex. Using a sensitive RNase protective assay, preliminary studies demonstrated the predicted regional distribution for the 5-HT2 receptor mRNA: levels of 5-HT2 mRNA were highest in frontal cortex (2.58 amol/micrograms of total RNA), intermediate in neostriatum, thalamus, and midbrain, and lowest in hippocampus, cerebellum, and choroid plexus. Chronic (10 or 14 days), but not acute (1 or 3 days), ECS treatment significantly increased levels of 5-HT2 receptor mRNA. ECS treatment resulted in a similar time-dependent up-regulation of 5-HT2 receptor ligand binding; chronic, but not acute, ECS treatment significantly increased levels of [3H]ketanserin ligand binding, confirming previous reports. Northern blot analysis demonstrated that 5-HT2 receptor mRNA occurs as two bands (approximately 5 and 6 kb in size), both of which were increased by chronic ECS treatment. The influence of antidepressant drug treatments on 5-HT2 receptor mRNA was also examined. Chronic fluoxetine treatment increased levels of 5-HT2 receptor mRNA, although levels of [3H]ketanserin ligand binding were not altered. In contrast, chronic administration of imipramine, mianserin, and tranylcypromine, treatments that decreased ligand binding, did not decrease levels of 5-HT2 receptor mRNA. In fact, mianserin treatment caused a small, but significant, increase in levels of receptor mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)