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Imipramine- and mianserin-induced acute cell injury in primary cultured rat hepatocytes: implication of different cytochrome P450 enzymes.

The antidepressants, imipramine and mianserin, have been reported to cause liver damage. We investigated a role of cytochrome P450 (CYP)-mediated formation of a reactive metabolite in antidepressant-induced acute cell injury using hepatocytes isolated from male and female Wistar rats, and male Dark Agouti rats, which have different relative abundance of CYP enzymes. Culture of the hepatocytes with imipramine and mianserin caused a marked decrease in glutathione followed by protein thiol, which preceded lactate dehydrogenase leakage. The decreases in glutathione and protein thiol contents by imipramine were significantly slower in hepatocytes from male Dark Agouti rats than those from male Wistar rats, whereas no significant sex difference in Wistar rats was observed. The decrease in thiol by mianserin was significantly slower in hepatocytes from female Wistar than those from male Wistar rats, whereas no significant differences were found between Wistar and Dark Agouti males. Results consistent with alteration of the thiols were obtained for lactate dehydrogenase leakage induced by imipramine and mianserin. These findings indicated that CYP-mediated metabolic activation was involved in acute cell injury induced by the antidepressants; namely a CYP2D enzyme(s), which is deficient in Dark Agouti rats, and a male specific CYP enzyme(s) were suggested to be responsible for the cytotoxicity of imipramine and mianserin, respectively.

Animals↗

Noradrenergic antidepressants: does chronic treatment increase or decrease nuclear CREB-P?

Chronic administration of noradrenergic antidepressants causes a desensitization of the beta adrenoceptor coupled adenylate cyclase system. In the present studies, we attempted to answer the question of whether or not this deamplification is reflected beyond the second messenger system. Nuclear CREB-P was determined in frontal cortex of rats following acute and chronic administration of desipramine (DMI) or reboxetine and in human fibroblasts following incubation for 48 hours with DMI, reboxetine or venlafaxine. Nuclear CREB-P in the frontal cortex was significantly decreased following chronic administration of DMI or reboxetine. Moreover, incubation of human fibroblasts with DMI or reboxetine, but not with venlafaxine, caused a highly significant reduction in nuclear CREB-P suggesting that the noradrenergic antidepressants exert direct effects beyond beta adrenoceptors. The results are consistent with the view that chronic treatment with antidepressants causes a net deamplification of the norepinephrine mediated signal transduction cascade which might "normalize" the increased noradrenergic activity evident in major depression.

Animals↗

The effects of antidepressant drugs on salivary flow and content of sodium and potassium ions in human parotid saliva.

Stimulated parotid saliva was collected, using the Carlson-Crittenden cup, from normal controls and patients on antidepressant drugs. The saliva from patients using amitriptyline, dothiepin (tricyclics), fluoxetine and paroxetine (selective serotonin re-uptake inhibitors; SSRI) was analysed for flow rate, [Na+] and [K+], and was compared with that from unmedicated, non-depressed volunteers for all variables. The tricyclic antidepressants produced a significant reduction in flow (amitriptyline, p < 0.01; dothiepin, p < 0.05), and consequent decrease in [Na+] and increase in [K+]. These effects were presumably due to muscarinic receptor blockade. The SSRIs produced no significant change in these variables. A prospective study of dothiepin in non-depressed patients confirmed that it decreases stimulated parotid flow. This finding also suggested that depression itself contributed little to the oral dryness observed in and reported by the depressed patients. The patients' subjective rating of oral dryness related well to a reduction in stimulated flow. This applied to those taking either tricyclics or SSRI, both showing a reduced flow rate relative to control (p < 0.001 and p < 0.05, respectively). This amounted to a 58% reduction in flow rate in the tricyclic group. The data suggest that measurement of stimulated parotid salivary flow is a reliable indicator of drug-induced oral dryness.

Adult↗

Antidepressant drugs given repeatedly change the binding of the dopamine D2 receptor agonist, [3H]N-0437, to dopamine D2 receptors in the rat brain.

The effects of antidepressants given in a single dose or repeatedly (10 mg/kg p.o., twice daily, 14 days) on binding to dopamine D2 receptors in the striatum and limbic forebrain of Wistar male rats were studied. [3H]N-0437, (2-(N[2,3(n)-3H]propyl-N-(2-thiofuranyl)-2'-ethylamino) -5-hydroxy-1,2,3,4-tetrahydronaphthalene), a dopamine D2 receptor agonist, was used as a ligand. Already a single dose of imipramine and fluoxetine caused a statistically significant decrease in the affinity of the ligand for dopamine D2 receptors in the striatum, but only at 72 h after drug administration. Also at 72 h after the single dose of mianserin a significant increase in the density of dopamine D2 receptors was observed. Repeated imipramine, amitriptyline and mianserin increased the affinity for dopamine D2 receptors in the striatum and in the limbic forebrain. Repeated fluoxetine increased that affinity in the striatum, but decreased it in the limbic forebrain. The density of dopamine D2 receptors was increased by the repeated administration of the antidepressants studied in the limbic forebrain, but was not changed in the striatum. The results obtained in the present study are in good agreement with the previously reported enhancement of behavioural responsiveness to dopamine and dopamine stimulants (dopamine D2 up-regulation) evoked by repeated treatment with antidepressants.

Amitriptyline↗

GABA(B) receptor function and subunit expression in the rat spinal cord as indicators of stress and the antinociceptive response to antidepressants.

Experiments were undertaken to examine whether once daily i.p. administration of either of two antidepressants used for the treatment of neuropathic pain, amitriptyline (10 mg/kg) and fluoxetine (5 mg/kg), to rats for 7 days modifies GABA(B) receptor function and subunit expression in the lumbar spinal cord. The results indicate that, as previously reported for desipramine, both amitriptyline and fluoxetine increase the pain threshold to a thermal stimulus, the expression of GABA(B(1)) subunits, and baclofen-stimulated [35S]GTPgammaS binding, a measure of GABA(B) receptor function. The effects of antidepressant administration on GABA(B(1b)) and GABA(B(2)) subunit expression in spinal cord are more variable than for GABA(B(1a)). It was also discovered that repeated daily exposure to a thermal stimulus or immobilization stress increases GABA(B(1a)) expression in the lumbar spinal cord, with no commensurate change in thermal pain threshold or GABA(B) receptor sensitivity. These results support a relationship between GABA(B) receptors and the action of antidepressants. The findings demonstrate that drug-induced increases in GABA(B) receptor function can occur independently of any change in GABA(B) receptor subunit expression and are consistent with the notion that GABA(B) receptor subunits have multiple functions, only one of which is dimerization to form GABA(B) receptors. The data also suggest that GABA(B) subunit gene expression may serve as a preclinical marker of antidepressant efficacy and of drug- or stress-induced modifications in central nervous system activity.

Amitriptyline↗

Biphasic change in BDNF gene expression following antidepressant drug treatment explained by differential transcript regulation.

Brain-derived neurotrophic factor (BDNF) has been suggested as a possible target for the treatment of depression. The effect by antidepressant drugs on BDNF mRNA expression is, however, strictly dependent on both treatment duration and time after the last administration. The rat BDNF gene itself is complex and expresses four different mRNA isoforms which can be regulated by different signaling cascades. The aim of the present study was to test the hypothesis that the previously shown biphasic action by the antidepressant drugs on total BDNF expression is explained by differential BDNF transcript regulation. For this purpose, we used in situ hybridization with exon-specific oligo nucleotides for exon V (total BDNF mRNA), exon I (protein synthesis-dependent transcripts), exon III and exon IV (immediate early-gene like-transcripts). Following an acute injection, all three drugs tested: fluoxetine, desipramine and TCP decreased total BDNF mRNA (exon V) as well as exon IV mRNA, while no significant effect was recorded for exons I and III mRNAs. In contrast chronic administration of all three drugs resulted in increased expression of exon V- and exon I-containing transcripts (fluoxetine and TCP only) but no significant changes were recorded for exon III and IV mRNAs. Electroconvulsive shock administration showed up-regulation of all four BDNF mRNAs following a single shock, but after repeated administration increases were restricted to exons I- and V-containing transcripts. In summary, this study shows clear evidence of differential BDNF transcript regulation following acute and chronic antidepressant drug treatment.

Animals↗

Effect of antidepressant drugs on 6-OHDA-treated mice in the FST.

There is growing evidence suggesting that dopamine could be indirectly involved in the appearance of behavioural effects of antidepressants. In this study, we induced a partial (over 70%) and non-reversible depletion of dopamine-containing neurons in mice by i.c.v. infusion of 6-OHDA. Then, we compared the antidepressant-like effect of drugs (citalopram, paroxetine, desipramine and imipramine) with or without dopamine depletion in the mice forced swimming test. Our results clearly show that lesion with 6-OHDA does not modify the response of mice to desipramine and imipramine, whereas dopamine depletion abolished the antidepressant-like effect of citalopram and paroxetine. It could then be suggested that antidepressant-like effect of selective serotonin reuptake inhibitors (paroxetine and citalopram) in the mice FST requires the activation of dopaminergic pathways to occur.

Animals↗

A comparative study of fluoxetine, moclobemide, and tianeptine in the treatment of posttraumatic stress disorder following an earthquake.

PURPOSE: Although antidepressant drugs have been proven as an effective treatment for posttraumatic stress disorder (PTSD), there are few comparative studies of antidepressants that are acting on different neurotransmitters. The main aim of this study is to compare the efficacy of different class of antidepressant drugs on the PTSD. SUBJECTS/MATERIALS AND METHODS: In this open label study, the patients who met DSM-IV criteria for PTSD were randomly assigned to flexible doses of fluoxetine, moclobemide, or tianeptine. After the first assessment, consecutive assessments were performed at the end of weeks 2, 4, 8, and 12 using clinician administered PTSD scale (CAPS) and Clinical Global Impression of Severity (CGI-S). Changes in the total score of CAPS and sub-scale scores of symptom clusters (re-experience, avoidance, and hyperarousal) were the main output of efficacy. All statistics were based on intention-to-treat and last-observation-carried-forward (LOCF) principles. RESULTS: Thirty-eight patients were assigned to fluoxetine, 35 patients were assigned to moclobemide, and 30 patients were assigned to tianeptine group. Gender distributions and mean ages of the treatment groups were not significantly different. Drop-out rates due to an adverse events or unknown reasons were not significantly different among fluoxetine (18.4%), moclobemide (14.3%), and tianeptine (20.0%) groups. All three treatments has led to a significant improvement in PTSD severity assessed with CAPS total score (ANOVA P < 0.001). Similarly, total scores of re-experiencing, avoidance, and hyperarousal clusters that are subscales of CAPS were significantly reduced by all three treatments (with ANOVA all P values < 0.001). There was not significant difference in terms of treatment effect between three groups. DISCUSSION: Treatment groups showed very similar improvement on all ratings scales. The findings support that fluoxetine, moclobemide, and tianeptine are all effective in the treatment of PTSD. Different mechanisms of action for these antidepressant drugs might result in the same common neurochemical end point. However, further studies using different classes of antidepressant drugs are needed.

Adult↗

Antidepressant-mediated reversal of abnormal behavior and neurodegeneration in mice following olfactory bulbectomy.

Olfactory bulbectomy is an established animal model of depression that has been mostly investigated in rats. As in human major depression, bulbectomy induces behavioral alterations that can be ameliorated by chronic antidepressant treatment. Furthermore, bulbectomy in rats is known to induce neurodegeneration in some brain areas. The aim of the present study was to evaluate patterns of behavioral alterations and neurodegeneration, and their drug-induced reversibility, in bulbectomized mice. Our results reveal that in mice bulbectomy increases locomotor activity and induces deficits in the passive avoidance test, comparable to the effects seen in rats. Bulbectomy also induced neuronal degeneration, visualized by incorporation of Fluoro-Jade B, in the piriform cortex and the posterolateral cortical amygdaloid nucleus (PLCo). Chronic treatment with the antidepressant amitriptyline protected neurons in both areas and efficiently reversed abnormal locomotor activity induced by bulbectomy. Treatment with citalopram was effective in reversing the behavioral deficits induced by bulbectomy, but did not protect against neurodegeneration. Our data indicate significant overlap between mice and rats in terms of behavioral alterations and neurodegeneration following olfactory bulbectomy. However, there are differences in drug-mediated reversibility of neurodegeneration suggesting that neurodegeneration and protection may be "second-order" features in this animal model of depression. This may also be relevant in the context of studies using genetically altered mice.

Amitriptyline↗

Sodium channel blockade may contribute to the analgesic efficacy of antidepressants.

UNLABELLED: Sodium channel blockers such as lidocaine, lamotrigine, and carbamazepine can be effective in the treatment of neuropathic pain. Though not approved for neuropathic pain indications, tricyclic antidepressants are often considered first-line treatment for conditions such as post-herpetic neuralgia and diabetic neuropathy. Several tricyclic antidepressants have been shown to block peripheral nerve sodium channels, which may contribute to their antihyperalgesic efficacy. In this study, we compared the sodium channel-blocking potency of a number of antidepressants, including tricyclic antidepressants and selective serotonin reuptake inhibitors. All compounds tested inhibited Na(V)1.7 in a state- and use-dependent manner, with affinities for the inactivated state ranging from 0.24 micromol/L for amitriptyline to 11.6 micromol/L for zimelidine. The tricyclic antidepressants were more potent blockers of Na(V)1.7. Moreover, IC(50)s for block of the inactivated state for amitriptyline, nortriptyline, imipramine, desipramine, and maprotiline were in the range of therapeutic plasma concentrations for both the treatment of depression as well as neuropathic pain. By contrast, fluoxetine, paroxetine, mianserine, and zimelidine had IC(50)s for Na(V)1.7 outside their therapeutic concentration ranges and generally were not efficacious against post-herpetic neuralgia or diabetic neuropathy. These results suggest that block of peripheral nerve sodium channels may contribute to the antihyperalgesic efficacy of certain antidepressants. PERSPECTIVE: Tricyclic antidepressants are often considered first-line treatment for neuropathic pain. Some tricyclic antidepressants block sodium channels, which may contribute to their antihyperalgesic efficacy. In the current study, we compared the potency of peripheral sodium channel blockade for several tricyclic antidepressants and selective serotonin reuptake inhibitors with their therapeutic efficacy.

Analgesics↗

G protein-activated inwardly rectifying K+ channel inhibition and rescue of weaver mouse motor functions by antidepressants.

Antidepressants, including tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), have been widely used for the treatment of not only depression but also other psychiatric disorders, although the molecular mechanisms of the drug effects have not yet been sufficiently revealed. Here, we investigated the in vivo effects of these antidepressants on G protein-activated inwardly rectifying K+ (GIRK) channels, which are important for regulating the excitability of various cells, by using weaver (wv) mice, which have mutant GIRK channels and show abnormal neuronal cell death and motor disturbances. First, we found that a widely used SSRI fluoxetine (also known as Prozac) effectively inhibited wv GIRK2 channels like wild-type GIRK channels, expressed in Xenopus oocytes. Next, we found that weaver motor disturbances were remarkably alleviated by chronic treatment with fluoxetine or desipramine. Furthermore, the chronic fluoxetine treatment substantially suppressed the abnormal neuronal cell death in the weaver mouse cerebellum and pontine nuclei. These results suggest that continuous inhibition of wv GIRK2 channels by a group of antidepressants caused substantial suppression of the neuronal cell death and resulted in improvement of motor abilities in weaver mice. These results provide evidence for in vivo GIRK channel inhibition by a group of antidepressants.

Animals↗

Sequential changes in BDNF mRNA expression and synaptic levels of AMPA receptor subunits in rat hippocampus after chronic antidepressant treatment.

Increased expression of brain-derived neurotrophic factor (BDNF) appears to be involved in the mechanism of action of antidepressant drugs. It has also been proposed that potentiation of the AMPA receptor (AMPAR) function may be useful in the treatment of depression. Here we looked for the time course of the effect of different doses of two antidepressants, desipramine (DMI) and paroxetine (PAR), which differentially affect monoamine reuptake, on BDNF mRNA expression in hippocampal subfields (CA1, CA3 and dentate gyrus) and levels of AMPAR subunits in total and membrane-enriched extracts from rat hippocampus. Acute antidepressant treatment changed neither BDNF mRNA expression nor AMPAR subunit levels. In chronic treatments, rats were treated daily with the antidepressants for 7-21 days. PAR produced a time- and dose-dependent increase of BDNF expression in the three hippocampal subfields examined. On the contrary, the effect of DMI on BDNF mRNA was neither dose- nor time-dependent. In rats receiving the same chronic antidepressant treatments, PAR produced a dose-dependent increase of GluR1 and GluR2/3 levels in the membrane fraction after a 3-week treatment, and not at earlier times. DMI increased the membrane levels of AMPAR subunits after a 3-week treatment with the lower dose tested. However, a higher dose, 15 mg/kg, did not produce any change in AMPAR subunits and reduced membrane levels of alpha-tubulin and PSD-95, possibly indicating a disorganization of membrane scaffolding proteins. The results suggest that paroxetine, but not desipramine, enhances synaptic plasticity in the hippocampus by increasing BDNF mRNA expression, which determines a later AMPAR subunit trafficking to synaptic membranes.

Animals↗

Antidepressant-like effect of nicotinamide adenine dinucleotide in the forced swim test in rats.

Nicotinamide adenine dinucleotide (NADH), a cosubstrate for energy transfer in the oxidative phosphorylation, has supposedly beneficial effects on central nervous system (CNS)-related diseases, e.g., shown in an open study with depressive patients. To our knowledge there are no data concerning the efficacy of NADH in animal tests. Acute effects of NADH and the precursor nicotinamide, compared to controls and the antidepressants desipramine and fluoxetine, were examined in the forced swim test (FST) in Wistar rats. NADH, but not nicotinamide, reduced immobility and increased swimming behaviour in the FST, with a minimum effective dose of 5 mg/kg. NADH-induced behavioural profile was similar to fluoxetine, but different from desipramine. Since NADH did not induce hyperlocomotion but even decreased motor activity in the open field test, the antidepressant-like effect cannot be attributed to an increase in motor activity. These data support an antidepressant potential of NADH.

Animals↗

Antidepressant effects of nicotine and fluoxetine in an animal model of depression induced by neonatal treatment with clomipramine.

The association between smoking and depression has been widely investigated. Most of these reports suggest that nicotine (NIC) may act as an antidepressant. To examine the suggested antidepressant effect of nicotine and its possible interaction with the serotonergic system, we assessed the effect of nicotine and fluoxetine (FLX) in an animal model of depression induced by neonatal treatment with clomipramine (CLI) and submitted to the forced swim test (FST). Results corroborated that CLI-treated rats displayed higher levels of immobility. After the administration of nicotine (0.4 mg/kg sc) acutely (1 day), subchonically (7 days), and chronically (14 days), CLI-treated rats significantly reduced the immobility and increased swimming without affecting climbing. These effects were similar to the effects induced for subchronic and chronic administration of the antidepressant fluoxetine (5 mg/kg sc), a selective serotonin re-uptake inhibitor. However, fluoxetine failed to affect immobility when it was administered acutely. No synergism was observed when both drugs were administered simultaneously. The present results further corroborate the antidepressant action of nicotine and fluoxetine. The increase of swimming during the FST has been linked to an increase of serotonergic activity. Thus, it could be possible that the antidepressant action of nicotine is mediated by the serotonergic system.

Animals↗

Evidence of a possible role of altered angiotensin function in the treatment, but not etiology, of depression.

BACKGROUND: Angiotensin-converting enzyme inhibitors are reportedly effective in the treatment of depression; furthermore, antidepressants decrease angiotensin function. It appears therefore that reduced angiotensin function may be important in the treatment of depression. The aims of this study were to elucidate the actions of antidepressants on angiotensin receptors; to investigate the antidepressant potential of an angiotensin antagonist; and to study angiotensin receptors in depressed puerperal women. METHODS: The effects of antidepressant drugs on angiotensin receptors and the relationship between mood and platelet receptors in puerperal women were investigated using radioligand binding. The antidepressant potential of the angiotensin antagonist losartan was assessed using the mouse forced swim test. RESULTS: Desipramine, but neither fluoxetine nor tranylcypromine, displaced angiotensin from its receptor; however, there was no significant relationship between receptor number and depressed mood. In the forced swim test losartan was shown to possess antidepressant like activity. CONCLUSIONS: These findings indicate that antidepressants differ in the mechanism by which they reduce angiotensin function, but the link between antidepressants and angiotensin is reiterated by the demonstration that losartan possesses antidepressant like activity. There is, however, no evidence of abnormal angiotensin receptors in women with depressed mood postpartum.

Adult↗

The 5-HT3 receptor agonist attenuates the action of antidepressants in the forced swim test in rats.

Involvement of 5-hydroxytryptamine (5-HT)3 receptors in action of antidepressants was examined in the forced swim test in rats. Rats were forced to swim in a cylinder for 15 min on day 1 and for 5 min on day 2. Imipramine, desipramine and mianserin, administered after the 15-min swim session on day 1 and before the 5-min swim test on day 2, dose-dependently decreased the duration of immobility in the swim test on day 2. 1-(m-Chlorophenyl)-biguanide (mCPBG) attenuated the decreased duration of immobility induced by imipramine, desipramine and mianserin, although mCPBG did not affect the duration of immobility when it was given alone. ICS205-930 dose-dependently decreased the duration of immobility in the swim test on day 2, and the effect of ICS205-930 was attenuated by mCPBG. These results suggest that the suppression of 5-HT3 receptor activity may contribute to the action of antidepressants.

Animals↗