Steady state concentrations of clomipramine and its major metabolite desmethylclomipramine in rat brain and serum after oral administration of clomipramine

Time Perception Test in IntelliCage System for Preclinical Study: Linking Depression and Serotonergic Modulation

Background/Objectives:: The link between serotonergic modulation and depression is under debate; however, serotonin reuptake inhibitors (SRIs) are still the first-choice medicine in this condition. Disturbances in time perception are also reported in depression with one of the behavioral schedules used to study interval timing, differential-reinforcement-learning-of-low-rate, having been shown to have high predictive validity for an antidepressant effect. Here, we introduce an IntelliCage research protocol of an interval bisection task that allows more ecologically valid and less time-consuming rodent examination and provides an example of its use to confirm the previously reported acute effect of an SRI, clomipramine, on interval timing (increase in bisection point, D50). Methods: Wistar male rats (n = 25, five groups of 5-8) were trained in the IntelliCage to discriminate between short (1 s) and long (4 s) LED light stimuli by nose poking at the corresponding (left/right) side of the IntelliCage chamber to obtain a drink. When 80% of correct responses were reached, the intermediate durations of 1.7, 2.5, and 3.3 s were introduced. The number of left/right choices for each stimulus and interval timing parameters (bisection point, D50, and timing precision), derived from them, were compared after saline and clomipramine (7 mg/kg, i.p) intraperitoneal administration. Results: Rats successfully learned the task within about a week of training. The slightly increased D50 after clomipramine confirmed previous studies. Conclusions: The introduced protocol has potential to be applicable to preclinical research on depression and potentially other psychopathology, where time perception can be disturbed.

Effect of Epigallocatechin-3-gallate on Stress-Induced Depression in a Mouse Model: Role of Interleukin-1β and Brain-Derived Neurotrophic Factor

Epigallocatechin 3-gallate (EGCG) is a natural polyphenolic antioxidant in green tea leaves with well-known health-promoting properties. However, the influence of EGCG on a chronic animal model of depression remains to be fully investigated, and the details of the molecular and cellular changes are still unclear. Therefore, the present study aimed to investigate the antidepressant effect of EGCG in mice subjected to chronic unpredictable mild stress (CUMS). After eight consecutive weeks of CUMS, the mice were treated with EGCG (200 mg/kg b.w.) by oral gavage for two weeks. A forced swimming test (FST) was used to assess depressive symptoms. EGCG administration significantly alleviated CUMS-induced depression-like behavior in mice. EGCG also effectively decreased serum interleukin-1β (IL-1β) and increased the mRNA expression levels of brain-derived neurotrophic factor (BDNF) in the hippocampal CA3 region of CUMS mice. Furthermore, electron microscopic examination of CA3 neurons in CUMS mice showed morphological features of apoptosis, loss or disruption of the myelin sheath, and degenerating synapses. These neuronal injuries were diminished with the administration of EGCG. The treatment effect of EGCG in CUMS-induced behavioral alterations was comparable with that of clomipramine hydrochloride (Anafranil), a tricyclic antidepressant drug. In conclusion, our study demonstrates that the antidepressive action of EGCG involves downregulation of serum IL-1β, upregulation of BDNF mRNA in the hippocampus, and reduction of CA3 neuronal lesions.

The Anti-inflammatory Effect of the Tricyclic Antidepressant Clomipramine and Its High Penetration in the Brain Might Be Useful to Prevent the Psychiatric Consequences of SARS-CoV-2 Infection

At the time of writing (December 2020), coronavirus disease 2019 (COVID-19) has already caused more than one million deaths worldwide, and therefore, it is imperative to find effective treatments. The “cytokine storm” induced by Severe Acute Respiratory Syndrome-Coronavirus type 2 (SARS-CoV-2) is a good target to prevent disease worsening, as indicated by the results obtained with tocilizumab and dexamethasone. SARS-CoV-2 can also invade the brain and cause neuro-inflammation with dramatic neurological manifestations, such as viral encephalitis. This could lead to potentially incapacitating long-term consequences, such as the development of psychiatric disorders, as previously observed with SARS-CoV. Several pathways/mechanisms could explain the link between viral infection and development of psychiatric diseases, especially neuro-inflammation induced by SARS-CoV-2. Therefore, it is important to find molecules with anti-inflammatory properties that penetrate easily into the brain. For instance, some antidepressants have anti-inflammatory action and pass easily through the blood brain barrier. Among them, clomipramine has shown very strong anti-inflammatory properties in vitro, in vivo (animal models) and human studies, especially in the brain. The aim of this review is to discuss the potential application of clomipramine to prevent post-infectious mental complications. Repositioning and testing antidepressants for COVID-19 management could help to reduce peripheral and especially central inflammation and to prevent the acute and particularly the long-term consequences of SARS-CoV-2 infection.

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

Many genetic variants in drug metabolizing enzymes and transporters have been shown to be relevant for treating psychiatric disorders. Associations are strong enough to feature on drug labels and for prescribing guidelines based on such data. A range of commercial tests are available; however, there is variability in included genetic variants, methodology, and interpretation. We herein provide relevant background for understanding clinical associations with specific variants, other factors that are relevant to consider when interpreting such data (such as age, gender, drug-drug interactions), and summarize the data relevant to clinical utility of pharmacogenetic testing in psychiatry and the available prescribing guidelines. We also highlight areas for future research focus in this field.

In Vitro and In Vivo Pipeline for Validation of Disease-Modifying Effects of Systems Biology-Derived Network Treatments for Traumatic Brain Injury-Lessons Learned

We developed a pipeline for the discovery of transcriptomics-derived disease-modifying therapies and used it to validate treatments in vitro and in vivo that could be repurposed for TBI treatment. Desmethylclomipramine, ionomycin, sirolimus and trimipramine, identified by in silico LINCS analysis as candidate treatments modulating the TBI-induced transcriptomics networks, were tested in neuron-BV2 microglial co-cultures, using tumour necrosis factor α as a monitoring biomarker for neuroinflammation, nitrite for nitric oxide-mediated neurotoxicity and microtubule associated protein 2-based immunostaining for neuronal survival. Based on (a) therapeutic time window in silico, (b) blood-brain barrier penetration and water solubility, (c) anti-inflammatory and neuroprotective effects in vitro (p < 0.05) and (d) target engagement of Nrf2 target genes (p < 0.05), desmethylclomipramine was validated in a lateral fluid-percussion model of TBI in rats. Despite the favourable in silico and in vitro outcomes, in vivo assessment of clomipramine, which metabolizes to desmethylclomipramine, failed to demonstrate favourable effects on motor and memory tests. In fact, clomipramine treatment worsened the composite neuroscore (p < 0.05). Weight loss (p < 0.05) and prolonged upregulation of plasma cytokines (p < 0.05) may have contributed to the worsened somatomotor outcome. Our pipeline provides a rational stepwise procedure for evaluating favourable and unfavourable effects of systems-biology discovered compounds that modulate post-TBI transcriptomics.

Distribution of clomipramine, citalopram, midazolam, and metabolites in skeletal tissue after chronic dosing in rats

In recent years, the use of skeletal tissue as an alternative matrix in forensic toxicology has received new interest. In cases where extreme decomposition has taken place, analysis of skeletal tissue is often the only option left. In this article, a fully validated method is presented and the distribution of clomipramine, citalopram, midazolam, and metabolites after chronically administration is examined within skeletal tissue. Rats were chronically dosed with respectively clomipramine, citalopram, or midazolam. Extracts were quantitatively analyzed using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Clomipramine, citalopram, and metabolites, respectively desmethylclomipramine and desmethylcitalopram are shown to be detectable in all bone types sampled. Midazolam and its metabolite α-OH-midazolam could not be detected. The absence of midazolam in extracts gives an indication that drugs with pKa values under physiological pH are badly or not incorporated in bone tissue. Bone and post-mortem blood concentrations were compared. A range of different bone types was compared and showed that the concentration is strongly dependent on the bone type. In concordance with previous publications, the humerus shows the highest drug levels. Skeletal tissue concentrations found ranged from 1.1 to 587.8 ng/g. Comparison of the same bone type between the different rats showed high variances. However, the drugs-metabolite ratio proved to have lower variances (<20%). Moreover, the drugs-metabolite ratio in the sampled bones is in close concordance to the ratios seen in blood within a rat. From this, we can assume that the drugs-metabolite ratio in skeletal tissue may prove to be more useful than absolute found concentration.

Intravenous lipid emulsion therapy for acute clomipramine intoxication in rats

Aim

In this study, to assess the utility of lipid emulsion (ILE) therapy as a treatment option for overdoses of lipophilic drugs, we examined the detoxification effect of ILE therapy in rats that were administered overdoses of the tricyclic antidepressant clomipramine hydrochloride (CMI).

Methods

Female Wistar rats were orally administered 50 mg/kg CMI five times in 2‐h intervals to examine whether intralipos accelerated the elimination of CMI in the peripheral blood. Rats were divided into the intralipos (i.v. 2 g/kg intralipos) and placebo (i.v. saline) groups. The concentrations of CMI and desmethylclomipramine (DMCMI), a metabolite of CMI, in blood were measured over time by high‐performance liquid chromatography. We then gave the animals 100 mg/kg CMI orally to examine whether intralipos could inhibit the distribution of CMI. The CMI and DMCMI concentrations in peripheral blood, liver, and brain were measured 60 min after intralipos administration.

Results

The blood concentration of CMI was significantly higher in the intralipos group than in the placebo group at 60 and 120 min. After a single administration of 100 mg/kg CMI, the ratio of the concentration of CMI in liver/serum was significantly lower in the intralipos group than in the placebo group. We also found a significantly faster elimination rate for CMI in peripheral blood in the intralipos group than in the placebo group.

Conclusion

The distribution of CMI from blood to tissue was suppressed by intralipos. Therefore, ILE therapy is a promising candidate for the treatment of overdoses of lipophilic drugs.

Anti-angiogenic drugs: direct anti-cancer agents with mitochondrial mechanisms of action

Components of the mitochondrial electron transport chain have recently gained much interest as potential therapeutic targets. Since mitochondria are essential for the supply of energy that is required for both angiogenic and tumourigenic activity, targeting the mitochondria represents a promising potential therapeutic approach for treating cancer. Here we investigate the established anti-angiogenesis drugs combretastatin A4, thalidomide, OGT 2115 and tranilast that we hypothesise are able to exert a direct anti-cancer effect in the absence of vasculature by targeting the mitochondria. Drug cytotoxicity was measured using the MTT assay. Mitochondrial function was measured in intact isolated mitochondria using polarography, fluorimetry and enzymatic assays to measure mitochondrial oxygen consumption, membrane potential and complex I-IV activities respectively. Combretastatin A4, OGT 2115 and tranilast were both shown to decrease mitochondrial oxygen consumption. OGT 2115 and tranilast decreased mitochondrial membrane potential and reduced complex I activity while combretastatin A4 and thalidomide did not. OGT 2115 inhibited mitochondrial complex II-III activity while combretastatin A4, thalidomide and tranilast did not. Combretastatin A4, thalidomide and OGT 2115 induced bi-phasic concentration-dependent increases and decreases in mitochondrial complex IV activity while tranilast had no evident effect. These data demonstrate that combretastatin A4, thalidomide, OGT 2115 and tranilast are all mitochondrial modulators. OGT 2115 and tranilast are both mitochondrial inhibitors capable of eliciting concentration-dependent reductions in cell viability by decreasing mitochondrial membrane potential and oxygen consumption.

Developmental emergence of an obsessive-compulsive phenotype and binge behavior in rats

RATIONALE

Obsessive-compulsive disorder (OCD) gradually emerges and reaches clinical significance during early adulthood. Whether a predisposition for OCD manifests as binge eating disorder earlier during adolescence is proposed.

OBJECTIVES

To further characterize how OCD-like behaviors increase across maturation and to determine whether an OCD-like predisposition increases the likelihood of binge eating during adolescence.

METHODS

Male and female Sprague-Dawley rats were injected with the tricyclic antidepressant clomipramine (CMI, 15 mg/kg) or saline vehicle twice daily between postnatal days 9-15. Both groups were tested for perseverative (spontaneous alternation) and anxiety-like (elevated plus maze; marble burying) behaviors during juvenility (day 28), adolescence (day 60), and adulthood (day 90). Both motivations to eat sucrose pellets and binge eating on fat were investigated.

RESULTS

Sex- and age-dependent increases in anxiety-like and perseverative behavior were observed in CMI subjects. Differences in consummatory behaviors emerged during late adolescence, while no significant differences in alternation or anxiety-like behaviors were detected between CMI and vehicle animals until adulthood. Adolescent CMI females consumed more sucrose pellets in 30 min relative to vehicle females, whereas adolescent CMI males consumed approximately half as much as vehicle males. Sucrose consumption did not differ between groups in adulthood. Adolescent CMI rats demonstrated more fat bingeing than vehicles, independent of sex.

CONCLUSIONS

OCD-like behaviors are emerging during adolescence, but sucrose consumption and fat bingeing in CMI-treated animals significantly precedes the appearance of anxiety and perseveration. This OCD-like phenotype emerges fully during adulthood, suggesting that eating may likely serve as a coping strategy in these animals.

The bio-distribution of the antidepressant clomipramine is modulated by chronic stress in mice: effects on behavior

Major depression (MD) is one of the most common psychiatric disorders, severely affecting the quality of life of millions of people worldwide. Despite the availability of several classes of antidepressants, treatment efficacy is still very variable and many patients do not respond to the treatment. Clomipramine (CMI), a classical and widely used antidepressant, shows widespread interindividual variability of efficacy, while the environmental factors contributing to such variability remain unclear. We investigated whether chronic stress modulates the bio-distribution of CMI, and as a result the behavioral response to CMI treatment in a mouse model of chronic social defeat stress (CSDS). Our results show that stress exposure increased anxiety-like and depressive-like behaviors and altered the stress response. Chronic defeat stress furthermore significantly altered CMI bio-distribution. Interestingly, CMI bio-distribution highly correlated with anxiety-like and depressive-like behaviors only under basal conditions. Taken together, we provide first evidence demonstrating that chronic stress exposure modulates CMI bio-distribution and behavioral responses. This may contribute to CMI’s broad interindividual variability, and is especially relevant in clinical practice.

Acute and subchronic treatments with selective serotonin reuptake inhibitors increase Nociceptin/Orphanin FQ (NOP) receptor density in the rat dorsal raphe nucleus; interactions between nociceptin/NOP system and serotonin

Nociceptin/Orphanin FQ is the endogenous ligand of NOP receptor, formerly referred to as the Opioid Receptor-Like 1 receptor. We have previously shown that NOP receptors were located on serotonergic neurons in the rat dorsal raphe nucleus, suggesting possible direct interactions between nociceptin and serotonin in this region, which is a target for antidepressant action. In the present study, we investigated further the link between Selective Serotonin Reuptake Inhibitor (SSRI) antidepressant treatments and the nociceptin/NOP receptor system. Intraperitoneal administration of the SSRI citalopram induced an increase in NOP-receptor density, measured by autoradiographic [(3)H] nociceptin binding, in the rat dorsal raphe nucleus, from the first to the 21st day of treatment. This effect was also observed with other SSRIs (sertraline, fluoxetine), but not with two tricyclic antidepressants (imipramine, clomipramine) and was abolished by pre-treatment with para-chlorophenylalanine, an inhibitor of serotonin synthesis. Using microdialysis experiments, we demonstrated that NOP-receptor activation by infusion of nociceptin 10(-6) M or 10(-5) M increased the level of extracellular serotonin in the dorsal raphe nucleus. This effect was abolished by co-infusion of the NOP-receptor antagonist UFP 101. These results confirm the existence of reciprocal interactions between serotonin and nociceptin/NOP transmissions in the dorsal raphe nucleus.

Inhibitory potencies of trimipramine and its main metabolites at human monoamine and organic cation transporters

RATIONALE

The antidepressant trimipramine shows an atypical pharmacological profile and its mechanism of action is still obscure.

OBJECTIVES

The present study investigated whether trimipramine and three of its metabolites interact with targets of other antidepressants, namely, the human monoamine transporters for noradrenaline (hNAT), serotonin (hSERT), and dopamine (hDAT), and with the human organic cation transporters (hOCT1, hOCT2, and hOCT3) which are expressed in the brain and are known to be involved in the uptake of monoamines.

METHODS

HEK293 cells heterologously expressing the abovementioned transporters were used to determine the inhibition of [(3)H]MPP(+) uptake by trimipramine and its main metabolites.

RESULTS

At concentrations up to 30 μM, all transporters, except hOCT3, were inhibited by all examined substances. With IC(50) values between 2 and 10 μM, trimipramine inhibited hSERT, hNAT, hOCT1, and hOCT2, whereas clearly higher concentrations were needed for half-maximal inhibition of hDAT. Desmethyl-trimipramine showed about the same potencies as trimipramine, whereas 2-hydroxy-trimipramine was less potent at hNAT, hSERT, and hOCT1. Trimipramine-N-oxide preferentially inhibited hSERT.

CONCLUSIONS

Neither trimipramine nor its metabolites are highly potent inhibitors of the examined monoamine transporters. However, since at a steady state the sum of the concentrations of the parent compound and its active metabolites is almost two times higher than the plasma concentration of trimipramine and since it is known that tricyclic antidepressants accumulate in the brain (up to tenfold), at least partial inhibition by trimipramine and its metabolites of hSERT and hNAT (but not of hOCT3) may contribute to the antidepressant action of trimipramine.

Regional distribution of clomipramine and desmethylclomipramine in rat brain and peripheral organs on chronic clomipramine administration

The tricyclic antidepressant (TCA) clomipramine has been widely used in psychiatry for over 40 years. More recently, its therapeutic potential as an antineoplastic drug has been identified. However, there are no prior data on regional distribution in the brain of clomipramine and its primary metabolite (desmethylclomipramine) after chronic oral administration. The aim of this study was to determine the concentrations of clomipramine and desmethylclomipramine in different rat-brain regions and to compare those with levels in plasma and peripheral organs after chronic oral treatment of Sprague Dawley rats (15 mg/kg) for 14 days. The levels of both parent TCA and metabolite were analysed by high-performance liquid chromatography in six brain regions (cortex, hypothalamus, hippocampus, striatum, brainstem and cerebellum), five peripheral organs and in plasma. Our data show that the cerebral cortex had the highest concentration of clomipramine (2.9 microg/mg), with successively lower concentrations in the hypothalamus, striatum, cerebellum, hippocampus and brainstem. Of the peripheral organs, the lungs and liver, had the highest levels of clomipramine, while in the heart, only the metabolite was detected. The plasma concentration (0.17 microg/ml or 0.48 microM) was comparable to that in the hippocampus and cerebellum (approximately 0.20 microg/mg). The differential distribution of clomipramine in different brain regions and the regional variation in clomipramine to desmethylclomipramine ratios have implications for the use of clomipramine in psychiatry and neuro-oncology.

Inhibition of glial inflammatory activation and neurotoxicity by tricyclic antidepressants

Glial activation and neuroinflammatory processes play an important role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and HIV dementia. Activated glial cells can secrete various proinflammatory cytokines and neurotoxic mediators, which may contribute to neuronal cell death. Inhibition of glial activation may alleviate neurodegeneration under these conditions. In the present study, the antiinflammatory and neuroprotective effects of tricyclic antidepressants were investigated using cultured brain cells as a model. The results showed that clomipramine and imipramine significantly decreased the production of nitric oxide or tumor necrosis factor-alpha (TNF-alpha) in microglia and astrocyte cultures. Clomipramine and imipramine also attenuated the expression of inducible nitric oxide synthase and proinflammatory cytokines such as interleukin-1beta and TNF-alpha at mRNA levels. In addition, clomipramine and imipramine inhibited IkappaB degradation, nuclear translocation of the p65 subunit of NF-kappaB, and phosphorylation of p38 mitogen-activated protein kinase in the lipopolysaccharide-stimulated microglia cells. Moreover, clomipramine and imipramine were neuroprotective as the drugs reduced microglia-mediated neuroblastoma cell death in a microglia/neuron co-culture. Therefore, these results imply that clomipramine and imipramine have antiinflammatory and neuroprotective effects in the central nervous system by modulating glial activation.

Inhibition of serotonin but not norepinephrine transport during development produces delayed, persistent perturbations of emotional behaviors in mice

Serotonin (5-HT) acts as a neurotransmitter, but also modulates brain maturation during early development. The demonstrated influence of genetic variants on brain function, personality traits, and susceptibility to neuropsychiatric disorders suggests a critical importance of developmental mechanisms. However, little is known about how and when developmentally perturbed 5-HT signaling affects circuitry and resulting behavior. The 5-HT transporter (5-HTT) is a key regulator of extracellular 5-HT levels and we used pharmacologic strategies to manipulate 5-HTT function during development and determine behavioral consequences. Transient exposure to the 5-HTT inhibitors fluoxetine, clomipramine, and citalopram from postnatal day 4 (P4) to P21 produced abnormal emotional behaviors in adult mice. Similar treatment with the norepinephrine transporter (NET) inhibitor, desipramine, did not adversely affect adult behavior, suggesting that 5-HT and norepinephrine (NE) do not share the same effects on brain development. Shifting our period of treatment/testing to P90/P185 failed to mimic the effect of earlier exposure, demonstrating that 5-HT effects on adult behavior are developmentally specific. We have hypothesized that early-life perturbations of 5-HT signaling affect corticolimbic circuits that do not reach maturity until the peri-adolescent period. In support of this idea, we found that abnormal behaviors resulting from postnatal fluoxetine exposure have a post-pubescent onset and persist long after reaching adult age. A better understanding of the underlying 5-HT sensitive circuits and how they are perturbed should lead to new insights into how various genetic polymorphisms confer their risk to carriers. Furthermore, these studies should help determine whether in utero exposure to 5-HTT blocking drugs poses a risk for behavioral abnormalities in later life.

Effect of chronic treatment with clomipramine on food intake, macronutrient selection and body weight gain in rats

Long-term treatment with clomipramine (CMI), a tricyclic antidepressant, induces food craving and body weight gain in patients. The present study investigated the effects of chronic treatment with CMI on total food intake, macronutrient selection, and body weight gain in rats. Male Wistar rats were maintained on a dietary self-selection regime with separate sources of protein, fat and carbohydrate. Animals received i.p. injections of CMI (0, 3, 10, 30 mg/kg) during 27 consecutive days. Food consumption and body weight were recorded daily and results were calculated as average of three consecutive days, namely during pre-treatment (3 d before pharmacological treatment), treatment (7th-9th; 16th-18th and 25th-27th days), and post-treatment (28th-33rd days). Results showed that CMI (30 mg/kg) significantly decreased energy intake during all treatment period, an effect that was related to a decrease in both carbohydrate-rich diet intake and body weight gain. At dose of 3 mg/kg CMI increased the total energy intake in the 16th-18th days, suggesting an apparent biphasic effect of chronic treatment with CMI on caloric intake. Chronic administration with CMI (27 d) did not alter protein-rich or fat-rich diet consumption. The main result of this study indicated that chronic treatment with CMI decreases rather than increase food consumption and body weight gain in rats exposed to a macronutrient self-selection procedure.

The effects of antidepressants on cyclic AMP-response element-driven gene transcription in a model cell system

The effects of the antidepressant drugs clomipramine (CLOM), desipramine (DMI), tianeptine (TIAN) and of norfluoxetine (NORF, the active metabolite of fluoxetine), were investigated in CHO cells expressing human beta2 adrenoceptors and a secreted placental alkaline phosphatase (SPAP) reporter gene to determine their actions on cyclic AMP-driven gene transcription. After 18 h of exposure, CLOM, DMI and NORF, but not TIAN, had biphasic effects on 1 microM isoprenaline-stimulated SPAP fsproduction with concentrations between 10 nM and 1 microM enhancing the maximal (E(max)) SPAP response, without changing EC50 values, but higher concentrations produced marked inhibitory effects. At nanomolar concentrations, CLOM and DMI increased expression of phospho-CREB (cyclic AMP response element binding protein). NORF was less effective but did significantly increase phospho-CREB at a concentration of 200 nM. TIAN had no effect. None of the antidepressants had any effect on CREB expression, nor on the accumulation of cyclic AMP. After prolonged exposure (7-21 days) to a low concentration (200 nM) of the antidepressants, the enhanced E(max) values for SPAP production evident after 18 h were not maintained but CLOM and DMI induced a significant leftward shift in the isoprenaline EC50 after a 7-day period of treatment and this was sustained at the 21 day time point. TIAN did not produce any significant changes. The results demonstrate that, in vitro, some but not all antidepressants can modify gene transcription via monoamine and cyclic AMP-independent mechanisms. The in vivo adaptive responses to TIAN probably involve alterations in different gene sets to those affected by other antidepressants.

Effects of physiological covariables on pharmacokinetic parameters of clomipramine in a large population of cats after a single oral administration

This study was conducted to confirm an interindividual variability in pharmacokinetic parameters of clomipramine in a large population of cats and to identify potential covariables that would explain the presence of such pharmacokinetic variability after a single dose of Clomicalm. Clomipramine hydrochloride was administered orally according to a weight-dose chart from 0.32 to 0.61 mg/kg, to 76 cats and five blood samples were then taken by direct venipuncture at 1, 3, 6, 12, and 24 h. Plasma concentrations of clomipramine and desmethylclomipramine (DCMP) were measured by LC-MS/MS. The Standard Two-Stage technique was used to assess differences and detect correlations between pharmacokinetic parameter estimates and individual covariables. A large interindividual variability in all pharmacokinetic parameters (CV% 64-124) was detected. Statistically significant gender-related differences were detected in MR and Cl/F, where female cats had a higher mean MR (0.53) and faster Cl/F (0.36 L/h.kg) than males (0.36 and 0.21 L/h.kg, respectively). No correlation could be found between clomipramine AUC0-24 h or DCMP AUC0-24 h and sedation scores. Further feline studies are required to assess these findings after multiple dosing of clomipramine and DCMP to allow clinical extrapolation.

Antidepressants and antipsychotic drugs colocalize with 5-HT3 receptors in raft-like domains

Despite different chemical structure and pharmacodynamic signaling pathways, a variety of antidepressants and antipsychotics inhibit ion fluxes through 5-HT3 receptors in a noncompetitive manner with the exception of the known competitive antagonists mirtazapine and clozapine. To further investigate the mechanisms underlying the noncompetitive inhibition of the serotonin-evoked cation current, we quantified the concentrations of different types of antidepressants and antipsychotics in fractions of sucrose flotation gradients isolated from HEK293 (human embryonic kidney 293) cells stably transfected with the 5-HT3A receptor and of N1E-115 neuroblastoma cells in relation to the localization of the 5-HT3 receptor protein within the cell membrane. Western blots revealed a localization of the 5-HT3 receptor protein exclusively in the low buoyant density (LBD) fractions compatible with a localization within raft-like domains. Also, the antidepressants desipramine, fluoxetine, and reboxetine and the antipsychotics fluphenazine, haloperidol, and clozapine were markedly enriched in LBD fractions, whereas no accumulation occurs for mirtazapine, carbamazepine, moclobemide, and risperidone. The concentrations of psychopharmacological drugs within LBD fractions was strongly associated with their inhibitory potency against serotonin-induced cation currents. The noncompetitive antagonism of antidepressants at the 5-HT3 receptor was not conferred by an enhancement of receptor internalization as shown by immunofluorescence studies, assessment of receptor density in clathrin-coated vesicles, and electrophysiological recordings after coexpression of a dominant-negative mutant of dynamin I, which inhibits receptor internalization. In conclusion, enrichment of antidepressants and antipsychotics in raft-like domains within the cell membrane appears to be crucial for their antagonistic effects at ligand-gated ion channels such as 5-HT3 receptors.

Chlorimipramine: A novel anticancer agent with a mitochondrial target

Mitochondria have been suggested to be a potential intracellular target for cancer chemotherapy. In this report, we demonstrate the ability of the tricyclic antidepressant chlorimipramine to kill human glioma cells in vitro by a molecular mechanism resulting in an increase in caspase 3 activity following inhibition of glioma oxygen consumption. Studies with isolated rat mitochondria showed that chlorimipramine specifically inhibited mitochondrial complex III activity, which causes decreased mitochondrial membrane potential as well as mitochondrial swelling and vacuolation. The use of chlorimipramine in human as an effective, non-toxic cancer therapeutic having a strong selectivity between cancer cells and normal cells on the basis of their mitochondrial function is discussed.

Serotonin reuptake inhibitors do not prevent 5,7-dihydroxytryptamine-induced depletion of serotonin in rat brain

Although the selective toxicity of 5,7-dihydroxytryptamine (5,7-DHT) is thought to depend on the drug's transport into serotonin (5HT) neurons via the 5HT transporter, few studies have critically examined this postulation. We therefore evaluated if 5,7-DHT-induced reductions in 5HT concentrations and synthesis rate in rat brain are blocked by pretreatment with 5HT-selective reuptake inhibitors. Rats pretreated with desipramine (DMI) (to prevent norepinephrine depletion) received intracerebroventricular injections of 5,7-DHT (5, 50, 100, 200 microg/rat) 30 min after fluoxetine (20 mg/kg ip). Forty-eight hours later, they received m-hydroxybenzylhydrazine 30 min before sacrifice. The concentrations of 5HT and 5-hydroxytryptophan (5HTP, an index of 5HT synthesis) were measured in hypothalamus, cortex and brainstem. Each 5,7-DHT dose produced significant reductions in 5HT and 5HTP concentrations in all regions examined (5 microg reduced 5HT but not 5HTP), effects that were not blocked by fluoxetine. Two other 5HT reuptake blockers (chlorimipramine, alaproclate) also failed to block the 5HT and 5HTP depleting actions of 5,7-DHT. Desipramine blocked 5,7-DHT-induced norepinephrine (NE) depletion. Pretreatment with the 5HT receptor antagonist metergoline, or the 5HT(1A) agonist 8-hydroxy-(di-n-propylamino)tetralin (to slow 5HT neuronal firing rate) also failed to antagonize the 5HT depleting action of 5,7-DHT. Together, the data strongly suggest that the mechanism by which 5,7-DHT depletes the brain of serotonin does not involve 5HT-transporter-mediated concentration of neurotoxin in 5HT neurons, may not involve 5HT receptor interaction, and does not depend on the firing rate of the 5HT neuron.

Antidepressants are functional antagonists at the serotonin type 3 (5-HT3) receptor

Antidepressants are commonly supposed to enhance serotonergic and/or noradrenergic neurotransmission by inhibition of neurotransmitter reuptake through binding to the respective neurotransmitter transporters or through inhibition of the monoamine oxidase. Using the concentration-clamp technique and measurements of intracellular Ca2+, we demonstrate that different classes of antidepressants act as functional antagonists at the human 5-HT3A receptor stably expressed in HEK 293 cells and at endogenous 5-HT3 receptors of rat hippocampal neurons and N1E-115 neuroblastoma cells. The tricyclic antidepressants desipramine, imipramine, and trimipramine, the serotonin reuptake inhibitor fluoxetine, the norepinephrine reuptake inhibitor reboxetine, and the noradrenergic and specific serotonergic antidepressant mirtazapine effectively reduced the serotonin-induced Na(+)- and Ca(2)(+)-currents in a dose-dependent fashion. This effect was voltage-independent and, with the exception of mirtazapine, noncompetitive. Desipramine, imipramine, trimipramine, and fluoxetine also accelerated receptor desensitization. Moclobemide and carbamazepine had no effect on the serotonin-induced cation current. By analyzing analogues of desipramine and carbamazepine, we found that a basic propylamine side chain increases the antagonistic potency of tricyclic compounds, whereas it is abolished by an uncharged carboxamide group. The antagonistic effects of antidepressants at the 5-HT3 receptor did not correlate with their effects on membrane fluidity. In conclusion, structurally different types of antidepressants modulate the function of this ligand-gated ion channel. This may represent a yet unrecognized pharmacological principle of antidepressants.

Influence of synaptic serotonin level on [18F]altanserin binding to 5HT2 receptors in man

The feasibility of in vivo serotonin 5HT(2) receptor binding measurement using [18F]altanserin as a radioligand has been well established. In this study, the postsynaptic receptor binding potential of this ligand was examined as a possible indicator of synaptic serotonin content after pharmacological challenge. Studies were performed in 11 subjects with a history of recurrent major depression. Six of them received serotonergic antidepressive treatment at the time of the experiment, the other five patients were untreated. Two PET measurements were carried out in each subject within 2 or 3 days. Before one of the measurements, 25 mg of the serotonin re-uptake inhibitor clomipramine were given intravenously, the other measurement was done without pharmacological challenge. The data were analyzed using non-linear least-square regression and Logan's graphical method. In the whole group of subjects, binding potential and distribution volume of altanserin decreased following clomipramine challenge. The decrease was between 14 (P=0.03) and 23% (P=0.004). This effect was mainly seen in subjects not on antidepressive medication. Clomipramine challenge probably increased the synaptic serotonin level, which competed with altanserin leading to the lowered binding potential. The paradigm might, thus, be useful to estimate serotonin release in vivo. Pretreatment with serotonergic antidepressants reduces the effect of clomipramine.

Effects of clomipramine on neuronal nicotinic acetylcholine receptors

The action of the tricyclic antidepressant clomipramine on membrane currents elicited by acetylcholine was studied in Xenopus oocytes expressing neuronal alpha2beta4 nicotinic acetylcholine receptors. Clomipramine inhibited the acetylcholine responses rapidly and reversibly, with a similar IC(50) when the oocytes were preincubated with clomipramine (1.3+/-0.2 microM) or when they were exposed simultaneously with acetylcholine and clomipramine (1.5+/-0.3 microM). The EC(50) was 39.9+/-2.1 microM for acetylcholine alone and 65.7+/-3.6 microM for acetylcholine in the presence of 2 microM clomipramine. The inhibitory effect of clomipramine was weakly voltage-dependent, with an electric distance of approximately 0.14. Moreover, clomipramine increased the rate of decay of currents elicited by acetylcholine. From all of these, we conclude that clomipramine reversibly and noncompetitively regulates neuronal alpha2beta4 nicotinic acetylcholine receptors by blocking the open receptor-channel complex at a site close to the extracellular vestibule of the channel. The actions of clomipramine on neuronal nicotinic acetylcholine receptors may play an important role in the treatment of mental depression and other mood disorders.