The hippocampal salt-inducible kinase 2-CREB-regulated transcription co-activator 1 system mediates the antidepressant actions of paroxetine in mice

The hippocampal salt-inducible kinase 2 (SIK2)-CREB-regulated transcription co-activator 1 (CRTC1) system has been demonstrated to participate in not only the pathogenesis of depression but also the antidepressant mechanisms of several antidepressant medications including fluoxetine, paroxetine, and mirtazapine. Like fluoxetine, paroxetine is also a widely used selective serotonin (5-HT) reuptake inhibitor (SSRI). Recent studies have indicated that paroxetine also modulates several pharmacological targets other than the 5-HT system. Here, we speculate that paroxetine regulates the hippocampal SIK2-CRTC1 system. Chronic stress models of depression, various behavioral tests, western blotting, co-immunoprecipitation, quantitative real-time reverse transcription PCR, and genetic knockdown were used together in the present study. Our results show that the antidepressant actions of paroxetine in mice models of depression were accompanied by its preventing effects against chronic stress on hippocampal SIK2, CRTC1, and CRTC1-CREB binding. In contrast, genetic knockdown of hippocampal CRTC1 notably abrogated the antidepressant effects of paroxetine in mice. In summary, regulating hippocampal SIK2 and CRTC1 participates in the antidepressant mechanism of paroxetine, extending the knowledge of its pharmacological targets.

Characterization of "microbiome-metabolome-immunity" in depressed rats with divergent responses to Paroxetine

OBJECTIVES

Selective serotonin reuptake inhibitors (SSRIs) are the first-line anti-depressants. Unfortunately, about 30 % depressed patients do not effectively respond to SSRIs. It is still unclear that the gastrointestinal characteristics of responders and non-responders, and the differences.

METHODS

Herein, we characterized gut microbiome and metabolome of depressed rats with differential responses to Paroxetine (PX) by 16S rRNA sequencing and 1H NMR-based metabolomics, respectively. On top of this, we constructed both inter- and inner-layer networks, intuitively showing the correlations among behavioral indicators, immune factors, intestinal bacteria, and differential metabolites.

RESULTS

Consequently, we found that depressed rats differently responded to PX, which could be divided into PX responsive (PX-R) and non-responsive (PX-N) groups. Firstly, the depressive behaviors of PX-R rats and PX-N rats significantly differed. Meanwhile, inflammatory balance was also characterized for depressed rats with different responses to PX. Overall, PX-R rats and PX-N rats exhibited differential gut microbiome and metabolome, including intestinal structures, intestinal functions, metabolic profiles, metabolites, and metabolic pathways.

LIMITATIONS

Metabolites that identified by metabolomics based on 1H NMR are not comprehensive enough.

CONCLUSIONS

Taken together, our study demonstrated that gut microbiome and metabolome, as well as related functions, are of significance in differential responses of depressed rats to PX, which might be novel insights in uncovering the mechanisms of differences in efficacies of antidepressants.

Enhanced interhemispheric resting-state functional connectivity of the visual network is an early treatment response of paroxetine in patients with panic disorder

This study aimed to detect alterations in interhemispheric interactions in patients with panic disorder (PD), determine whether such alterations could serve as biomarkers for the diagnosis and prediction of therapeutic outcomes, and map dynamic changes in interhemispheric interactions in patients with PD after treatment. Fifty-four patients with PD and 54 healthy controls (HCs) were enrolled in this study. All participants underwent clinical assessment and a resting-state functional magnetic resonance imaging scan at (i) baseline and (ii) after paroxetine treatment for 4 weeks. A voxel-mirrored homotopic connectivity (VMHC) indicator, support vector machine (SVM), and support vector regression (SVR) were used in this study. Patients with PD showed reduced VMHC in the fusiform, middle temporal/occipital, and postcentral/precentral gyri, relative to those of HCs. After treatment, the patients exhibited enhanced VMHC in the lingual gyrus, relative to the baseline data. The VMHC of the fusiform and postcentral/precentral gyri contributed most to the classification (accuracy = 87.04%). The predicted changes were accessed from the SVR using the aberrant VMHC as features. Positive correlations (p < 0.001) were indicated between the actual and predicted changes in the severity of anxiety. These findings suggest that impaired interhemispheric coordination in the cognitive-sensory network characterized PD and that VMHC can serve as biomarkers and predictors of the efficiency of PD treatment. Enhanced VMHC in the lingual gyrus of patients with PD after treatment implied that pharmacotherapy recruited the visual network in the early stages.

Role of serotonin, estrogen, and TNF-α in the paroxetine-impaired steroidogenesis and testicular macrophages polarization

BACKGROUND

Paroxetine, a selective serotonin reuptake inhibitor (SSRI) antidepressant, has caused male sexual dysfunction; however, the paroxetine mechanisms of action in testes are still unclear.

OBJECTIVES

Paroxetine serotonergic effects in testes were evaluated, focusing on steroidogenesis and the correlation between macrophages population and possible TNF-α-derived oxidative stress. We also verified whether the changes are reversible following treatment interruption.

MATERIALS AND METHODS

Adult rats received paroxetine (PG35 and PG65) or tap water (CG) for 35 days. PG65 was maintained without treatment for 30 more days. Intratesticular testosterone (IT), nitrite, and malondialdehyde concentrations were measured. To confirm serotonergic and estrogenic effects, Htr1b and Esr1 expressions were analyzed. The daily sperm production (DSP), frequency of abnormal seminiferous tubules (ST), SC number, ST area, and Leydig cells nuclear area (LCnu) were evaluated. TUNEL+ germ cells, M1 (CD68+ ), and M2 (Perls+ ) macrophages were quantified. 17β-HSD7, CYP19A1, NDRG2, oxytocin, TNF-α, and iNOS were evaluated by immunoreactions. Oxytocin and NDRG2 protein levels as well as Tnfa mRNA expression were also analyzed.

RESULTS

The Htr1b downregulation in testes confirmed the paroxetine serotonergic effect. The testicular sections showed abnormal ST frequency, ST atrophy and reduction of DSP, LCnu, SC number and Perls+ macrophages. TUNEL+ germ cells and LC were associated with strong NDRG2 immunoexpression. Paroxetine reduced IT levels and 17β-HSD7 immunoexpression in parallel to increased CYP19A1, oxytocin, TNF-α and iNOS. Esr1 and Tnfa overexpression and increased number of CD68+ macrophages were also observed together with high nitrite and malondialdehyde levels. Most parameters were not recovered in PG65.

CONCLUSIONS

Paroxetine serotonergic effect impairs LC steroidogenesis, via aromatization, increasing estrogen/testosterone ratio, which in turn upregulate NDRG2, promoting apoptosis, and impairing sperm production. Serotonin-estrogen pathways may be responsible for M2/M1 polarization, Tnfa upregulation, and induction of oxidative stress. The unrecovered testicular changes after treatment discontinuation are due to persistent paroxetine serotonin/estrogen effects.

In vitro effects of selective serotonin reuptake inhibitors on Cryptococcus gattii capsule and biofilm

Infections caused by Cryptococcus gattii mainly affect immunocompetent individuals and the treatment presents important limitations. This study aimed to validate the efficacy of selective serotonin reuptake inhibitors (SSRI), fluoxetine hydrochloride (FLH), and paroxetine hydrochloride (PAH) in vitro against C. gattii. The antifungal activity of SSRI using the microdilution method revealed a minimal inhibitory concentration (MIC) of 31.25 µg/ml. The combination of FLH or PAH with amphotericin B (AmB) was analyzed using the checkerboard assay and the synergistic effect of SSRI in combination with AmB was able to reduce the SSRI or AmB MIC values 4-8-fold. When examining the effect of SSRI on the induced capsules, we observed that FLH and PAH significantly decreased the size of C. gattii capsules. In addition, the effects of FLH and PAH were evaluated in biofilm biomass and viability. The SSRI were able to reduce biofilm biomass and biofilm viability. In conclusion, our results indicate the use of FLH and PAH exhibited in vitro anticryptococcal activity, representing a possible future alternative for the cryptococcosis treatment.

Solanidine is a sensitive and specific dietary biomarker for CYP2D6 activity

BACKGROUND

Individual assessment of CYP enzyme activities can be challenging. Recently, the potato alkaloid solanidine was suggested as a biomarker for CYP2D6 activity. Here, we aimed to characterize the sensitivity and specificity of solanidine as a CYP2D6 biomarker among Finnish volunteers with known CYP2D6 genotypes.

RESULTS

Using non-targeted metabolomics analysis, we identified 9152 metabolite features in the fasting plasma samples of 356 healthy volunteers. Machine learning models suggested strong association between CYP2D6 genotype-based phenotype classes with a metabolite feature identified as solanidine. Plasma solanidine concentration was 1887% higher in genetically poor CYP2D6 metabolizers (gPM) (n = 9; 95% confidence interval 755%, 4515%; P = 1.88 × 10-11), 74% higher in intermediate CYP2D6 metabolizers (gIM) (n = 89; 27%, 138%; P = 6.40 × 10-4), and 35% lower in ultrarapid CYP2D6 metabolizers (gUM) (n = 20; 64%, - 17%; P = 0.151) than in genetically normal CYP2D6 metabolizers (gNM; n = 196). The solanidine metabolites m/z 444 and 430 to solanidine concentration ratios showed even stronger associations with CYP2D6 phenotypes. Furthermore, the areas under the receiver operating characteristic and precision-recall curves for these metabolic ratios showed equal or better performances for identifying the gPM, gIM, and gUM phenotype groups than the other metabolites, their ratios to solanidine, or solanidine alone. In vitro studies with human recombinant CYP enzymes showed that solanidine was metabolized mainly by CYP2D6, with a minor contribution from CYP3A4/5. In human liver microsomes, the CYP2D6 inhibitor paroxetine nearly completely (95%) inhibited the metabolism of solanidine. In a genome-wide association study, several variants near the CYP2D6 gene associated with plasma solanidine metabolite ratios.

CONCLUSIONS

These results are in line with earlier studies and further indicate that solanidine and its metabolites are sensitive and specific biomarkers for measuring CYP2D6 activity. Since potato consumption is common worldwide, this biomarker could be useful for evaluating CYP2D6-mediated drug-drug interactions and to improve prediction of CYP2D6 activity in addition to genotyping.

Effect of the sEH inhibitor AUDA on arachidonic acid metabolism and NF-κB signaling of rats with postpartum depression-like behavior

OBJECTIVE

To investigate whether sEH inhibitor AUDA can mitigate postpartum depression (PPD)-like symptoms in the rat model and regulate the AA/NF-κB pathway to suppress the inflammatory response in the prefrontal lobes of PPD rats.

METHODS

Five groups of Sprague Dawley rats were used: normal, sham operated, PPD model, AUDA, and paroxetine hydrochloride. During the 21-day treatment period, animals in all groups underwent assessments (open field test, forced swimming test, and sucrose consumption) for depression-like behavior. At the conclusion of the treatment period, animals in all study groups were euthanized and various proteins in the prefrontal lobes were measured.

RESULTS

Depression-like behavior in rats was attenuated by AUDA. In the prefrontal lobes of PPD rats, levels of 5-LOX, COX-2, sEH, IL-1β, IL- 6, p65, p-p65, P-IκBα, NF-κB p65, and GFAP were increased while levels of epoxyeicosatrienoic acids and 5-HT were decreased. AUDA reversed these changes, thus having a similar effect as the classic antidepressant paroxetine hydrochloride.

CONCLUSION

AUDA may constrain AA/NF-κB in the prefrontal cortex of PPD rats, thus inhibiting the inflammatory response and ultimately attenuating postpartum depression-like behavior.

Cardioprotective Effects of the GRK2 Inhibitor Paroxetine on Isoproterenol-Induced Cardiac Remodeling by Modulating NF-κB Mediated Prohypertrophic and Profibrotic Gene Expression

Pathological cardiac remodeling is associated with cardiovascular disease and can lead to heart failure. Nuclear factor-kappa B (NF-κB) is upregulated in the hypertrophic heart. Moreover, the expression of the G-protein-coupled receptor kinase 2 (GRK2) is increased and linked to the progression of heart failure. The inhibitory effects of paroxetine on GRK2 have been established. However, its protective effect on IκBα/NFκB signaling has not been elucidated. This study investigated the cardioprotective effect of paroxetine in an animal model of cardiac hypertrophy (CH), focusing on its effect on GRK2-mediated NF-κB-regulated expression of prohypertrophic and profibrotic genes. Wistar albino rats were administered normal saline, paroxetine, or fluoxetine, followed by isoproterenol to induce CH. The cardioprotective effects of the treatments were determined by assessing cardiac injury, inflammatory biomarker levels, histopathological changes, and hypertrophic and fibrotic genes in cardiomyocytes. Paroxetine pre-treatment significantly decreased the HW/BW ratio (p < 0.001), and the expression of prohypertrophic and profibrotic genes Troponin-I (p < 0.001), BNP (p < 0.01), ANP (p < 0.001), hydroxyproline (p < 0.05), TGF-β1 (p < 0.05), and αSMA (p < 0.01) as well as inflammatory markers. It also markedly decreased pIκBα, NFκB(p105) subunit expression (p < 0.05) and phosphorylation. The findings suggest that paroxetine prevents pathological cardiac remodeling by inhibiting the GRK2-mediated IκBα/NF-κB signaling pathway.

Continuous home cage monitoring of activity and sleep in mice during repeated paroxetine treatment and discontinuation

RATIONALE

Non-invasive home cage monitoring is emerging as a valuable tool to assess the effects of experimental interventions on mouse behaviour. A field in which these techniques may prove useful is the study of repeated selective serotonin reuptake inhibitor (SSRI) treatment and discontinuation. SSRI discontinuation syndrome is an under-researched condition that includes the emergence of sleep disturbances following treatment cessation.

OBJECTIVES

We used passive infrared (PIR) monitoring to investigate changes in activity, sleep, and circadian rhythms during repeated treatment with the SSRI paroxetine and its discontinuation in mice.

METHODS

Male mice received paroxetine (10 mg/kg/day, s.c.) for 12 days, then were swapped to saline injections for a 13 day discontinuation period and compared to mice that received saline injections throughout. Mice were continuously tracked using the Continuous Open Mouse Phenotyping of Activity and Sleep Status (COMPASS) system.

RESULTS

Repeated paroxetine treatment reduced activity and increased behaviourally-defined sleep in the dark phase. These effects recovered to saline-control levels within 24 h of paroxetine cessation, yet there was also evidence of a lengthening of sleep bouts in the dark phase for up to a week following discontinuation.

CONCLUSIONS

This study provides the first example of how continuous non-invasive home cage monitoring can be used to detect objective behavioural changes in activity and sleep during and after drug treatment in mice. These data suggest that effects of paroxetine administration reversed soon after its discontinuation but identified an emergent change in sleep bout duration, which could be used as a biomarker in future preclinical studies to prevent or minimise SSRI discontinuation symptoms.

Paroxetine's effect on the proinflammatory cytokine stimulation and intracellular signaling pathways in J774.2 cells

Paroxetine is extensively utilized in the management of depressive and anxious conditions. Paroxetine works by increasing serotonin levels in nerve cells in the brain. However, limited information is available regarding the direct effects of paroxetine on macrophage cells. Macrophages are a type of leukocytes involved in the body's immune response, playing a crucial role in combating infections. The impact of paroxetine on macrophages has been explored in research, although a comprehensive understanding is still pending. This study aimed to research the potential of administering paroxetine to J774.2 macrophage cells to stimulate the release of GM-CSF, TNF-α, IL-12p40, and IL-6 cytokines. Additionally, we examined the mechanisms of action of paroxetine on the p38 signaling pathway, which is involved in cytokine production, and the PI3K pathway, which is an important mechanism in intracellular signaling. Our findings revealed that paroxetine induced an inflammatory response in macrophages by promoting cytokine synthesis in a non-lipopolysaccharide (LPS) environment. We observed that paroxetine triggered the inflammatory response through the PI3K signaling pathway while suppressing the p38 signaling pathway.

Impact of CYP2D6 Genotype on Paroxetine Serum Concentration

BACKGROUND

Paroxetine is a selective serotonin reuptake inhibitor metabolized by cytochrome P450 (CYP)2D6. Only small-scale studies have reported the impact of CYP2D6 genotype on paroxetine exposure, and international guidelines differ in their recommendations on whether paroxetine should be administered according to CYP2D6 genotype. To clarify this issue, the aim of the present study was to investigate the impact of CYP2D6 genotype on paroxetine serum concentration in a large population of patients after adjusting for CYP2C19 genotype, age, and sex.

METHODS

Patients from a therapeutic drug monitoring database with records on their paroxetine serum concentrations and CYP2D6 and CYP2C19 genotyping between 2010 and 2021 were included in the study. The impact of CYP2D6 and CYP2C19 genotypes, age, and sex on the paroxetine concentration-to-dose (C/D) ratio was investigated by multiple linear regression analysis. Patients treated with relevant CYP inhibitors or inducers were excluded.

RESULTS

In total, 304 patients were included in the study: 17 CYP2D6 poor metabolizers (PMs), 114 intermediate metabolizers (IMs), 168 extensive metabolizers (EMs), and 5 ultrarapid metabolizers. Multiple linear regression analysis showed that CYP2D6 IMs and PMs had 2.2-fold and 3.8-fold higher paroxetine C/D-ratios than extensive metabolizers, respectively ( P < 0.001). Patients who were CYP2C19 IMs (n = 70) or PMs (n = 13) had 1.6-fold higher paroxetine C/D ratio than extensive metabolizers ( P = 0.04). An age ≥65 years was associated with a 2.9-fold increased C/D ratio ( P < 0.001), whereas sex was not significantly associated with paroxetine exposure.

CONCLUSIONS

The present study showed that CYP2D6 genotype is of significant importance for paroxetine dose adjustments. For CYP2D6 PMs, 25% of the regular paroxetine starting dose may be sufficient, whereas CYP2D6 IMs could receive 50% of the regular dosage. This well-powered study shows that the guidelines should consider the importance of CYP2D6 genotype for personalized dosing of paroxetine.

Paroxetine Attenuates Chondrocyte Pyroptosis and Inhibits Osteoclast Formation by Inhibiting NF-κB Pathway Activation to Delay Osteoarthritis Progression

Background

Osteoarthritis (OA), a common chronic joint disease, is characterized by cartilage degeneration and subchondral bone reconstruction. NF-κB signaling pathway-activated inflammation and NLRP3-induced pyroptosis play essential roles in the development of OA. In this study, we examine whether paroxetine can inhibit pyroptosis and reduce osteoclast formation, thereby delaying the destruction of knee joints.

Methods

We employed high-density cultures, along with quantitative polymerase chain reactions and Western blotting techniques, to investigate the effects of paroxetine on extracellular matrix synthesis and degradation. The expression levels of NF-κB and pyroptosis-related signaling pathway proteins were examined by Western blotting and immunofluorescence. Furthermore, the impact of paroxetine on RANKL-induced osteoclast formation was evaluated through TRAP staining and F-actin ring fluorescence detection. To investigate the role of paroxetine in vivo, we constructed a mouse model with destabilization of the medial meniscus (DMM) surgery. Safranin O-Fast Green staining, Hematoxylin-Eosin staining, and immunohistochemistry were conducted to observe the extent of knee joint cartilage deformation. In addition, TRAP staining was used to observe the formation of osteoclasts in the subchondral bone.

Results

In the in vitro experiments with ATDC5, paroxetine treatment attenuated IL-1β-induced activation of the pyroptosis-related pathway and suppressed extracellular matrix catabolism by inhibiting the NF-kB signaling pathway. In addition, paroxetine treatment decreased the expression of RANKL-induced osteoclast marker genes and reduced osteoclast formation. In animal experiments conducted in vivo, mice treated with paroxetine exhibited thicker knee cartilage with a smoother surface compared to the DMM group. Additionally, the formation of osteoclasts in the subchondral bone was reduced in the paroxetine-treated mice. Further analysis revealed that paroxetine treatment played a role in preserving the balance of the extracellular matrix and delaying knee joint degeneration.

Conclusion

Paroxetine can inhibit pyroptosis and reduce osteoclast formation via inhibiting the NF-κB signaling pathway, suggesting that it may have therapeutic effects in patients with OA.

Retrospective evaluation of the efficacy of daily paroxetine/tadalafil combination in patients with premature ejaculation and erectile dysfunction

OBJECTIVE

Premature ejaculation (PE) and erectile dysfunction (ED) are sexual dysfunction diseases affecting males. The phosphodiesterase type 5 (PDE5) inhibitors such as tadalafil are used to treat ED whereas selective serotonin reuptake inhibitors (SSRIs) are preferred for PE. Most of the patients with ED also suffer from PE simultaneously. The combined drug therapies are commonly preferred as they favor elevated intra-vaginal ejaculation latency time (IELT) scores and improved sexual function. The study aimed to evaluate the efficacy and safety of daily paroxetine and tadalafil combination therapy in patients with PE and ED.

PATIENTS AND METHODS

A total of 81 PE patients with ED were enrolled in the study. Patients were treated with daily paroxetine 20 mg and tadalafil 5 mg for 4 weeks. Pre- and post-treatment IELT, premature ejaculation profile (PEP), and International Index of Erectile Function-Erectile Function (IIEF-EF) scores of the patients were analyzed.

RESULTS

The mean IELT and PEP index scores, and mean IIEF-EF values improved after combination therapy (p<0.001 for each). When lifelong and acquired PE+ED patients were compared, significant improvements were observed in IELT, PEP, and IIEF-EF scores in both groups (p<0.001).

CONCLUSIONS

Even though the treatment methods are different, combined therapies to treat simultaneous PE and ED presence are effective compared to monotherapies. However, there is still no definitive treatment that can cure all subtypes of PE or ED.

Antibacterial activity of paroxetine against Staphylococcus aureus and possible mechanisms of action

Aim: To evaluate the antibacterial activity of paroxetine alone and associated with oxacillin against isolates of methicillin-sensitive and -resistant Staphylococcus aureus. Materials & methods: The broth microdilution and checkerboard techniques were used, with investigation of possible mechanisms of action through flow cytometry, fluorescence microscopy and molecular docking, in addition to scanning electron microscopy for morphological analysis. Results: Paroxetine showed a MIC of 64 μg/ml and bactericidal activity, mostly additive interactions in combination with oxacillin, evidence of action on genetic material and membrane, morphological changes in microbial cells and influence on virulence factors. Conclusion: Paroxetine has antibacterial potential from the perspective of drug repositioning.

GRK2 participation in cardiac hypertrophy induced by isoproterenol through the regulation of Nrf2 signaling and the promotion of NLRP3 inflammasome and oxidative stress

OBJECTIVE

In cases of heart failure, cardiac hypertrophy may be caused by the upregulation of G-protein-coupled receptor kinase 2 (GRK2). Both NLRP3 inflammasome and oxidative stress contribute to cardiovascular disease. In this study, we clarified the effect of GRK2 on cardiac hypertrophy in H9c2 cells induced by isoproterenol (ISO) and examined the underlying mechanisms.

METHODS

We randomly categorized H9c2 cells into five groups: an ISO group, a paroxetine plus ISO group, a GRK2 small-interfering RNA (siRNA) plus ISO group, a GRK2 siRNA combined with ML385 plus ISO group, and a control group. To determine the effect of GRK2 on cardiac hypertrophy induced by ISO, we carried out CCK8 assays, RT-PCR, TUNEL staining, ELISA assay, DCFH-DA staining, immunofluorescence staining, and western blotting.

RESULTS

By using paroxetine or siRNA to inhibit GRK2, we significantly decreased cell viability; reduced the mRNA levels of ANP, BNP, and β-MHC; and limited the apoptosis rate and protein levels of cleaved caspase-3 and cytochrome c in H9c2 cells treated with ISO. We also found that oxidative stress induced by ISO could be mitigated with paroxetine or GRK2 siRNA. This result was validated by decreased activities of the antioxidant enzymes CAT, GPX, and SOD and increased MDA levels and ROS production. We observed that the protein expression of NLRP3, ASC, and caspase-1 and the intensity of NLRP3 could be inhibited by paroxetine or GRK2 siRNA. Both paroxetine and GRK2 siRNA were able to abolish the increase in GRK2 expression induced by ISO. They also could increase protein levels of HO-1, nuclear Nrf2, and Nrf2 immunofluorescence intensity; however, they could not change the protein level of cytoplasmic Nrf2. By combining treatment with ML385, we were able to reverse GRK2 inhibition on H9c2 cells treated with ISO.

CONCLUSION

According to the results of this study, GRK2 participated in cardiac hypertrophy induced by ISO by mitigating NLRP3 inflammasome and oxidative stress through the signaling of Nrf2 in H9c2 cells.

Management of Menopausal Symptoms: A Review

IMPORTANCE

Menopause, due to loss of ovarian follicular activity without another pathological or physiological cause, typically occurs between the ages of 45 years and 56 years. During the menopausal transition, approximately 50% to 75% of women have hot flashes, night sweats, or both (vasomotor symptoms) and more than 50% have genitourinary symptoms (genitourinary syndrome of menopause [GSM]).

OBSERVATIONS

Vasomotor symptoms typically last more than 7 years and GSM is often chronic. Efficacious treatments for women with bothersome vasomotor symptoms or GSM symptoms include hormonal and nonhormonal options. Systemic estrogen alone or combined with a progestogen reduces the frequency of vasomotor symptoms by approximately 75%. Oral and transdermal estrogen have similar efficacy. Conjugated equine estrogens (CEE) with or without medroxyprogesterone acetate (MPA) were the only hormonal treatments for which clinical trials were designed to examine cardiovascular events, venous thromboembolism, and breast cancer risk. Compared with placebo, the increased risk of stroke and venous thromboembolism associated with CEE (with or without MPA) and breast cancer (with use of CEE plus MPA) is approximately 1 excess event/1000 person-years. Low-dose CEE plus bazedoxifene is not associated with increased risk of breast cancer (0.25%/year vs 0.23%/year with placebo). Bioidentical estrogens approved by the US Food and Drug Administration (with identical chemical structure to naturally produced estrogens, and often administered transdermally) also are available to treat vasomotor symptoms. For women who are not candidates for hormonal treatments, nonhormonal approaches such as citalopram, desvenlafaxine, escitalopram, gabapentin, paroxetine, and venlafaxine are available and are associated with a reduction in frequency of vasomotor symptoms by approximately 40% to 65%. Low-dose vaginal estrogen is associated with subjective improvement in GSM symptom severity by approximately 60% to 80%, with improvement in severity by 40% to 80% for vaginal prasterone, and with improvement in severity by 30% to 50% for oral ospemifene.

CONCLUSIONS AND RELEVANCE

During the menopausal transition, approximately 50% to 75% of women have vasomotor symptoms and GSM symptoms. Hormonal therapy with estrogen is the first-line therapy for bothersome vasomotor symptoms and GSM symptoms, but nonhormonal medications (such as paroxetine and venlafaxine) also can be effective. Hormone therapy is not indicated for the prevention of cardiovascular disease.

Antidepressant-induced increase in GluA2 expression does not translate in changes of AMPA receptor-mediated synaptic transmission at CA3/CA1 synapses in rats

Chronic treatment with serotonin selective reuptake inhibitors or tryciclic antidepressant drugs in rodents has been shown to increase the expression of GluA1 and/or GluA2 AMPA receptor (AMPAR) subunits in several brain areas, including the hippocampus. These changes in AMPAR composition have been suggested to result in increased glutamatergic neurotransmission and possibly underlie enhanced hippocampal synaptic plasticity through the increased availability of calcium-permeable AMPARs, specifically at CA3/CA1 synapses. However, the possibility that chronic treatment with antidepressants actually results in strengthened glutamatergic neurotransmission in CA1 has poorly been investigated. Here, we studied whether chronic treatment with the multimodal antidepressant drug trazodone mimicked the effect of paroxetine on the expression of AMPAR subunits in male wistar rat hippocampus and whether these drugs produced a parallel facilitation of field excitatory postsynaptic potentials (fEPSP) responses evoked by activation of CA3/CA1 synapses in dorsal hippocampal slices. In addition, we investigated whether the quality of glutamatergic AMPARs involved in basal neurotransmission was changed by altered subunit expression, e.g. leading to appearance of calcium-permeable AMPARs. We found a significant increase in GluA2 subunit expression following treatment with trazodone or paroxetine for twenty-one days, but not after seven-days treatment. In contrast, we did not find any significant changes in fEPSP responses supporting either a facilitation of glutamatergic neurotransmission in basal conditions or the appearance of functional calcium-permeable AMPARs at CA3/CA1 pyramidal neuron synapses. Thus, neurochemically-detected increases in the expression of AMPAR subunits cannot directly be extrapolated in increased number of functioning receptors and/or facilitated basal neurotransmission.

The Effect of Irisin on Thyroid Hormone Levels in Chronic Paroxetine-Treated Rats

It is known that serotonin reuptake inhibitors (SSRIs), which are widely used in mood disorders, affect the hypothalamic-pituitary-thyroid axis activity. In this study, we investigated the effect of paroxetine, an SSRI, on thyroid hormone levels in rats. We also examined the role of irisin, a newly discovered potential regulatory hormone for metabolism, on paroxetine-induced changes. A total of 64 Sprague-Dawley female and male rats were randomly divided into four subgroups for each gender and treated as follows: sham-operated control (vehicle), paroxetine (treated with 20 mg/kg paroxetine by oral gavage), irisin (100 ng/kg/day for 28 days with mini-osmotic pumps), and paroxetine + irisin group (n = 8). Serum fasting free triiodothyronine (fT3) and free thyroxine (fT4) levels were measured by automated chemiluminescence method. Serum thyroid-stimulating hormone (TSH) level was determined with enzyme-linked immunosorbent analysis (ELISA). Compared to the sham control group (p < 0.05), the significantly reduced fT4 and TSH serum levels in paroxetine-treated male animals were markedly increased by subcutaneous irisin perfusion. fT3 levels significantly increased in both irisin (4.35 ± 0.17 pq/mL) and paroxetine + irisin groups (4.51 ± 0.19 pq/mL) compared to sham control (3.60 ± 0.23 pq/mL) and paroxetine groups (3.57 ± 0.12 pq/mL) (p < 0.05). It was observed that serum fT3, fT4, and TSH levels decreased in female animals receiving paroxetine compared to the sham control group. Subcutaneous administration of irisin increased these hormone levels. However, these changes were not statistically significant. These results suggested that irisin may play a role in the mechanism underlying the beneficial effects of exercise in preventing SSRI-related side effects by increasing thyroid hormone levels, which were decreased by paroxetine.

The Antidepressant Paroxetine Reduces the Cardiac Sodium Current

A considerable amount of literature has been published on antidepressants and cardiac ion channel dysfunction. The antidepressant paroxetine has been associated with Brugada syndrome and long QT syndrome, albeit on the basis of conflicting findings. The cardiac voltage-gated sodium channel (Na_V1.5) is related to both of these syndromes, suggesting that paroxetine may have an effect on this channel. In the present study, we therefore carried out patch clamp experiments to examine the effect of paroxetine on human Na_V1.5 channels stably expressed in human embryonic kidney 293 (HEK-293) cells as well as on action potentials of isolated rabbit left ventricular cardiomyocytes. Additionally, computer simulations were conducted to test the functional effects of the experimentally observed paroxetine-induced changes in the Na_V1.5 current. We found that paroxetine led to a decrease in peak Na_V1.5 current in a concentration-dependent manner with an IC₅₀ of 6.8 ± 1.1 µM. In addition, paroxetine caused a significant hyperpolarizing shift in the steady-state inactivation of the Na_V1.5 current as well as a significant increase in its rate of inactivation. Paroxetine (3 µM) affected the action potential of the left ventricular cardiomyocytes, significantly decreasing its maximum upstroke velocity and amplitude, both of which are mainly regulated by the Na_V1.5 current. Our computer simulations demonstrated that paroxetine substantially reduces the fast sodium current of human left ventricular cardiomyocytes, thereby slowing conduction and reducing excitability in strands of cells, in particular if conduction and excitability are already inhibited by a loss-of-function mutation in the Na_V1.5 encoding SCN5A gene. In conclusion, paroxetine acts as an inhibitor of Na_V1.5 channels, which may enhance the effects of loss-of-function mutations in SCN5A.

Paroxetine treatment in an animal model of depression improves sperm quality

Depression in mammals is known to be associated with poor reproductive capacity. In males, it has been associated with decreased efficiency of spermatogenesis as well as the production of spermatozoa of reduced structural and functional integrity. Although antidepressants are effective in correcting depressive states, there is controversy regarding their effectiveness in restoring male reproductive function. Here, using an animal model of depression induced by a forced swim test, we confirmed that depression is accompanied by impaired male reproductive function. We further show that administration of a conventional antidepressant of the serotonin reuptake inhibitor class (paroxetine) impairs male reproductive performance in terms of sperm production and quality when administered to healthy animals. Intriguingly, when paroxetine is administered to "depressed" animals, it resulted in a complete restoration of the animal's ability to produce sperm that appears to be as capable of meeting the parameters evaluated here as those of control animals. The one-carbon cycle (1CC) is one of the most important metabolic cycles that include the methionine and folate cycles and plays a major role in DNA synthesis, amino acids, and also the production of antioxidants. Our results show that depression affects the main components of this cycle and paroxetine on healthy mice increases homocysteine levels, decreases glycine and vitamin B12, while in depressed mice, it increases folate levels and decreases vitamin B12. Thus, paroxetine exerts negative impacts on male reproductive function when administered to healthy animals and it well correlate with the altered sperm parameters and functions of depressed animals, and its mechanism remains to be explored.

The Effects of Paroxetine on Benthic Microbial Food Web and Nitrogen Transformation in River Sediments

Paroxetine is a common pharmaceutical to treat depression and has been found to pose threats to aquatic organisms. However, little is known about the effects of paroxetine on the nutrient cycle in aquatic environments. Therefore, DNA metabarcoding is used in this study to analyze the effects of paroxetine on multi-trophic microorganisms and nitrogen transformation in river sediments. Although paroxetine has no significant effect on the diversity of microbenthos, changes in benthic nitrogen-converting bacteria are consistent with the change in the various forms of nitrogen in the sediment, indicating that paroxetine affects the nitrogen conversion process by affecting nitrogen-converting bacteria. In addition, it is found that paroxetine has the ability to influence nitrogen transformation in an indirect way by affecting the trophic transfer efficiency of higher trophic levels (meiofauna and protozoa, protozoa and protozoa), subsequently affecting the growth of nitrogen-converting bacteria through a top-down mechanism (i.e., predation).The results show that paroxetine affects nitrogen transformation directly by affecting nitrogen-converting bacteria and indirectly through top-down effects, emphasizing that the assessment of paroxetine's ecological risks should consider species within different trophic levels.

Effect of Paroxetine or Quetiapine Combined With Oxycodone vs Oxycodone Alone on Ventilation During Hypercapnia: A Randomized Clinical Trial

IMPORTANCE

Opioids can cause severe respiratory depression by suppressing feedback mechanisms that increase ventilation in response to hypercapnia. Following the addition of boxed warnings to benzodiazepine and opioid products about increased respiratory depression risk with simultaneous use, the US Food and Drug Administration evaluated whether other drugs that might be used in place of benzodiazepines may cause similar effects.

OBJECTIVE

To study whether combining paroxetine or quetiapine with oxycodone, compared with oxycodone alone, decreases the ventilatory response to hypercapnia.

DESIGN, SETTING, AND PARTICIPANTS

Randomized, double-blind, crossover clinical trial at a clinical pharmacology unit (West Bend, Wisconsin) with 25 healthy participants from January 2021 through May 25, 2021.

INTERVENTIONS

Oxycodone 10 mg on days 1 and 5 and the following in a randomized order for 5 days: paroxetine 40 mg daily, quetiapine twice daily (increasing daily doses from 100 mg to 400 mg), or placebo.

MAIN OUTCOMES AND MEASURES

Ventilation at end-tidal carbon dioxide of 55 mm Hg (hypercapnic ventilation) using rebreathing methodology assessed for paroxetine or quetiapine with oxycodone, compared with placebo and oxycodone, on days 1 and 5 (primary) and for paroxetine or quetiapine alone compared with placebo on day 4 (secondary).

RESULTS

Among 25 participants (median age, 35 years [IQR, 30-40 years]; 11 female [44%]), 19 (76%) completed the trial. The mean hypercapnic ventilation was significantly decreased with paroxetine plus oxycodone vs placebo plus oxycodone on day 1 (29.2 vs 34.1 L/min; mean difference [MD], -4.9 L/min [1-sided 97.5% CI, -∞ to -0.6]; P = .01) and day 5 (25.1 vs 35.3 L/min; MD, -10.2 L/min [1-sided 97.5% CI, -∞ to -6.3]; P < .001) but was not significantly decreased with quetiapine plus oxycodone vs placebo plus oxycodone on day 1 (33.0 vs 34.1 L/min; MD, -1.2 L/min [1-sided 97.5% CI, -∞ to 2.8]; P = .28) or on day 5 (34.7 vs 35.3 L/min; MD, -0.6 L/min [1-sided 97.5% CI, -∞ to 3.2]; P = .37). As a secondary outcome, mean hypercapnic ventilation was significantly decreased on day 4 with paroxetine alone vs placebo (32.4 vs 41.7 L/min; MD, -9.3 L/min [1-sided 97.5% CI, -∞ to -3.9]; P < .001), but not with quetiapine alone vs placebo (42.8 vs 41.7 L/min; MD, 1.1 L/min [1-sided 97.5% CI, -∞ to 6.4]; P = .67). No drug-related serious adverse events were reported.

CONCLUSIONS AND RELEVANCE

In this preliminary study involving healthy participants, paroxetine combined with oxycodone, compared with oxycodone alone, significantly decreased the ventilatory response to hypercapnia on days 1 and 5, whereas quetiapine combined with oxycodone did not cause such an effect. Additional investigation is needed to characterize the effects after longer-term treatment and to determine the clinical relevance of these findings.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04310579.

Effect of Human Cytochrome P450 2D6 Polymorphism on Progesterone Hydroxylation

BACKGROUND AND OBJECTIVES

Herein, hydroxylation activities at the 6β-position and 21-position of progesterone mediated by human cytochrome P450 (CYP) 2D6 and its variants and the effects of psychotropic drugs on these hydroxylation activities were compared to clarify whether CYP2D6 polymorphisms and psychotropic drugs impact neurosteroid levels in the brain.

METHODS

Progesterone was incubated with CYP2D6.1, CYP2D6.2 (Arg296Cys, Ser486Thr), CYP2D6.10 (Pro34Ser, Ser486Thr), and CYP2D6.39 (Ser486Thr) in the absence or presence of typical psychotropic drugs (fluvoxamine, fluoxetine, paroxetine, fluphenazine, and milnacipran) and endogenous steroids (testosterone and cortisol). Then, 6β- and 21-hydroxyprogesterone levels were determined by high-performance liquid chromatography.

RESULTS

Although the Michaelis-Menten constants (Km) for progesterone 6β- and 21-hydroxylation reactions mediated by the different CYP2D6 variants were similar, the maximal velocity (Vmax) values of the reactions mediated by CYP2D6.1 and CYP2D6.2 were the highest, followed by those mediated by CYP2D6.39 and CYP2D6.10. Thus, the of progesterone 6β- and/or 21-hydroxylation reactions mediated by CYP2D6.1 and CYP2D6.2 showed the highest Vmax/Km values, followed by the reactions mediated by CYP2D6.39. All investigated compounds inhibited progesterone 21-hydroxylation mediated by CYP2D6 variants at high concentrations. Interestingly, at low concentrations, fluoxetine increased progesterone 21-hydroxylation mediated by CYP2D6.1, but not that mediated by CYP2D6.2 or CYP2D6.10. In addition, the Km value for CYP2D6.2 was elevated in the presence of fluoxetine, whereas the value for CYP2D6.1 was unaltered; however, Vmax values of both CYP2D6.1 and CYP2D6.2 were increased. Paroxetine competitively inhibited CYP2D6.1- and CYP2D6.2-mediated progesterone 21-hydroxylation.

CONCLUSIONS

These results suggest that CYP2D6 polymorphism can affect the stimulation/inhibition of progesterone 21-hydroxylation.

SSRI antidepressants differentially modulate serotonin reuptake and release in Drosophila

Selective serotonin reuptake inhibitor (SSRI) antidepressants are commonly prescribed treatments for depression, but their effects on serotonin reuptake and release are not well understood. Drosophila melanogaster, the fruit fly, expresses the serotonin transporter (dSERT), the major target of SSRIs, but real-time serotonin changes after SSRIs have not been characterized in this model. The goal of this study was to characterize effects of SSRIs on serotonin concentration and reuptake in Drosophila larvae. We applied various doses (0.1-100 μM) of fluoxetine (Prozac), escitalopram (Lexapro), citalopram (Celexa), and paroxetine (Paxil), to ventral nerve cord (VNC) tissue and measured optogenetically-stimulated serotonin release with fast-scan cyclic voltammetry (FSCV). Fluoxetine increased reuptake from 1 to 100 μM, but serotonin concentration only increased at 100 μM. Thus, fluoxetine occupies dSERT and slows clearance but does not affect concentration. Escitalopram and paroxetine increased serotonin concentrations at all doses, but escitalopram increased reuptake more. Citalopram showed lower concentration changes and faster reuptake profiles compared with escitalopram, so the racemic mixture of citalopram does not change reuptake as much as the S-isomer. Dose response curves were constructed to compare dSERT affinities and paroxetine showed the highest affinity and fluoxetine the lowest. These data demonstrate SSRI mechanisms are complex, with separate effects on reuptake or release. Furthermore, dynamic serotonin changes in Drosophila are similar to previous studies in mammals. This work establishes how antidepressants affect serotonin in real-time, which is useful for future studies that will investigate pharmacological effects of SSRIs with different genetic mutations in Drosophila.

Beneficial effects of irisin in experimental paroxetine-induced hyperprolactinemia

OBJECTIVE

It is known that selective serotonin reuptake inhibitors (SSRIs), represent an important and effective treatment of depression and other psychological disorders, these medications can increase prolactin levels mainly through activation of the serotonergic pathway. In this study, we aimed to determine the beneficial effects of irisin on paroxetine, a SSRI, induced hyperprolectinemia and in some other reproductive hormonal changes associated with hyperprolactinemia.

METHODS

Thirty two male Spraque-Dawley rats were used and divided into four groups including sham-operated control (vehicle), irisin (100 ng/kg/day for 28 days with mini-osmotic pumps), paroxetine (treated with 20 mg/kg paroxetine by oral gavage), irisin and paroxetine+irisin groups (n = 8). Serum prolactin (PRL), kisspeptin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone and 5-alpha reductase levels were determined with enzyme-linked immunosorbent analysis (ELISA).

RESULTS

In animals treated with paroxetine, PRL level increased and testosterone level decreased significantly (p < 0.05). Serum LH level was significantly increased in the group, but no significant changes were observed in the FSH, kisspeptin and 5-alpha reductase levels. Serum prolactin levels was significantly decreased in the group treated with irisin. While no significant difference was observed in kisspeptin, FSH and 5-alpha reductase levels, an increase in serum LH and testosterone levels with irisin administration (p < 0.05).

CONCLUSION

In conclusion, chronic irisin exposure may reverse paroxetine-induced hyperprolactinemia. These results indicate that irisin may have the potential to be used as a therapeutic agent by primarily affecting paroxetine-induced increased prolactin and decreased testosterone levels.

Paroxetine effects on morphine analgesic tolerance in rats

OBJECTIVES

To alleviate different pain intensities, morphine administration has been extensively used. However, prolonged administration of morphine leads to a progressive decline of its analgesic effect which limits their overall utility. Morphine tolerance is considered as a challenging issue for the treatment of both acute and chronic pain. We conducted this study in rats to investigate the effect of paroxetine on morphine tolerance when used preemptively or after morphine tolerance had developed.

METHODS

Male Wistar rats (weight 250-300 g, n=10) were used to evaluate the effects of paroxetine on tolerance to morphine. In order to induce tolerance, daily intraperitoneal injection of morphine (7 mg/kg) was done. After tolerance induction, a group of animals received intraperitoneal injection of 10 mg/kg paroxetine 30 min prior to each morphine dose. In another trial, to investigate the potential of paroxetine to prevent tolerance to morphine, animals were pretreated with 10 mg/kg paroxetine 30 min before morphine administration. In the control groups, 10 mL/kg of saline was injected. The behavioral test (tail-flick test) was done for all groups.

RESULTS

Our data showed that paroxetine significantly reversed tolerance to morphine when used after tolerance induction (p<0.001). However, administration of paroxetine before occurrence of tolerance had no effect.

CONCLUSIONS

We conclude that paroxetine could decrease tolerance to morphine when used after the occurrence of morphine tolerance, while it was not able to prevent morphine tolerance when administered preemptively.

ETHICAL COMMITTEE NUMBER

IRIB.SBMU.MSP.REC.1394.098.

Role of P34S, G169R, R296C, and S486T Substitutions in Ligand Access and Catalysis for Cytochrome P450 2D6 Allelic Variants CYP2D6*14A and CYP2D6*14B

BACKGROUND

Genetic polymorphism of cytochrome P450 (CYP) contributes to variability in drug metabolism, clearance, and response. This study aimed to investigate the functional and molecular basis for altered ligand binding and catalysis in CYP2D6*14A and CYP2D6*14B, two unique alleles common in the Asian population.

METHODS

CYP proteins expressed in Escherichia coli were studied using the substrate 3-cyano-7- ethoxycoumarin (CEC) and inhibitor probes (quinidine, fluoxetine, paroxetine, terbinafine) in the enzyme assay. Computer modelling was additionally used to create three-dimensional structures of the CYP2D6*14 variants.

RESULTS

Kinetics data indicated significantly reduced intrinsic clearance in CYP2D6*14 variants, suggesting that P34S, G169R, R296C, and S486T substitutions worked cooperatively to alter the conformation of the active site that negatively impacted the deethylase activity of CYP2D6. For the inhibition studies, IC50 values decreased in quinidine, paroxetine, and terbinafine but increased in fluoxetine, suggesting a varied ligand-specific susceptibility to inhibition. Molecular docking further demonstrated the role of P34S and R296C in altering access channel dimensions, thereby affecting ligand access and binding and subsequently resulting in varied inhibition potencies.

CONCLUSION

In summary, the differential selectivity of CYP2D6*14 variants for the ligands (substrate and inhibitor) was governed by the alteration of the active site and access channel architecture induced by the natural mutations found in the alleles.

Melancholic features (DSM-IV) predict but do not moderate response to antidepressants in major depression: an individual participant data meta-analysis of 1219 patients

It is sometimes clinically believed that major depression with melancholic features is more responsive to antidepressants than non-melancholic depression. Proper analysis and, therefore, valid evidence to support or refute this common clinical lore is lacking. The sample was taken from three placebo-controlled randomized trials of duloxetine, escitalopram and paroxetine (n = 1219). We conducted a two-step individual participant data meta-analysis to combine linear mixed-effects regressions modeling melancholic features as prognostic factor (variable that predicts overall response regardless of the treatments) and as effect modifier (variable that predict differential response to drug over placebo). Melancholic features represented a statistically significant prognostic factor for greater reduction in depression severity both on antidepressants and on placebo, especially after 4 weeks of treatment. However, they were not an effect modifier of the antidepressant treatment through the acute phase treatment: in other words. The superiority of antidepressants over placebo was not influenced by the melancholic features. The treatment decision-making as to the benefits of antidepressant treatment for patients with major depression should not be influenced by the presence or absence of melancholic features.

Attenuating effect of paroxetine on memory impairment following cerebral ischemia-reperfusion injury in rat: The involvement of BDNF and antioxidant capacity

Memory impairments are frequently reported in patients suffering from brain ischemic diseases. Oxidative/nitrosative stress, synaptic plasticity, and brain-derived neurotrophic factor (BDNF) are involved in the physiopathology of brain ischemia-induced memory disorders. In the present study, the effect of paroxetine as an efficacious antidepressant medication with antioxidant properties was evaluated on passive avoidance memory deficit following cerebral ischemia in rats. Transient occlusion of common carotid arteries was applied to induce ischemia-reperfusion injury in male Wistar rats. Paroxetine (5, 10, 20 mg/kg) was administered intraperitoneally once daily before (for 3 days) or after (for 7 days) the induction of ischemia. A week after ischemia-reperfusion injury, passive avoidance memory, long-term potentiation (LTP), BDNF levels, total antioxidant capacity, the activity of antioxidant enzymes (including catalase, glutathione peroxidase, and superoxide dismutase), the concentration of malondialdehyde (MDA), and nitric oxide (NO) were investigated in the hippocampus. In the passive avoidance test, paroxetine significantly increased the step-through latency and decreased the time spent in the dark compartment. This affirmative function of paroxetine on the passive avoidance memory was accompanied by the improvement of hippocampal LTP and an obvious augmentation in the BDNF contents. Besides, paroxetine caused a significant rise in the total antioxidant capacity and antioxidant enzyme activity; while decreased the hippocampal levels of NO and MDA. It was ultimately attained that paroxetine attenuates cerebral ischemia-induced passive avoidance memory dysfunction in rats by the enhancement of hippocampal synaptic plasticity and BDNF content together with the suppression of oxidative/nitrosative stress.

Emotional and interpersonal mechanisms in community SSRI treatment of social anxiety disorder

BACKGROUND

Affective and interpersonal behavioural patterns characteristic of social anxiety disorder show improvement during treatment with serotonin agonists (e.g., selective serotonin reuptake inhibitors), commonly used in the treatment of social anxiety disorder. The present study sought to establish whether, during community psychopharmacological treatment of social anxiety disorder, changes in positive or negative affect and agreeable or quarrelsome behaviour mediate improvement in social anxiety symptom severity or follow from it.

METHODS

Adults diagnosed with social anxiety disorder (n = 48) recorded their interpersonal behaviour and affect naturalistically in an event-contingent recording procedure for 1-week periods before and during the first 4 months of treatment with paroxetine. Participants and treating psychiatrists assessed the severity of social anxiety symptoms monthly. A multivariate latent change score framework examined temporally lagged associations of change in affect and interpersonal behaviour with change in social anxiety symptom severity.

RESULTS

Elevated agreeable behaviour and positive affect predicted greater subsequent reduction in social anxiety symptom severity over the following month of treatment. Elevated negative affect, but not quarrelsome behaviour, predicted less subsequent reduction in symptom severity.

LIMITATIONS

Limitations included limited assessment of extreme behaviour (e.g., violence) that may have precluded examining the efficacy of paroxetine because of the lack of a placebo control group.

CONCLUSION

The present study suggests that interpersonal behaviour and affect may be putative mechanisms of action for serotonergic treatment of social anxiety disorder. Prosocial behaviour and positive affect increase during serotonergic treatment of social anxiety disorder. Specifically, modulating agreeable behaviour, positive affect and negative affect in individuals' daily lives may partially explain and refine clinical intervention.

Neuropeptide Y as Alternative Pharmacotherapy for Antidepressant-Resistant Social Fear

In many social anxiety disorder (SAD) patients, the efficacy of antidepressant therapy is unsatisfactory. Here, we investigated whether mice deficient for the lysosomal glycoprotein acid sphingomyelinase (ASM−/−) represent an appropriate tool to study antidepressant-resistant social fear. We also investigated whether neuropeptide Y (NPY) reduces this antidepressant-resistant social fear in ASM−/− mice, given that NPY reduced social fear in a mouse model of SAD, namely social fear conditioning (SFC). We show that neither chronic paroxetine nor chronic amitriptyline administration via drinking water were successful in reducing SFC-induced social fear in ASM−/− mice, while the same treatment reduced social fear in ASM+/− mice and completely reversed social fear in ASM+/+ mice. This indicates that the antidepressants paroxetine and amitriptyline reduce social fear via the ASM-ceramide system and that ASM−/− mice represent an appropriate tool to study antidepressant-resistant social fear. The intracerebroventricular administration of NPY, on the other hand, reduced social fear in ASM−/− mice, suggesting that NPY might represent an alternative pharmacotherapy for antidepressant-resistant social fear. These results suggest that medication strategies aimed at increasing brain NPY concentrations might improve symptoms of social fear in SAD patients who fail to respond to antidepressant treatments.

Effect of Paroxetine on the Neuropathic Pain: A Molecular Study

Background

Neuropathic pain, due to peripheral nerve damage, has influenced millions of people living all over the world. It has been shown that paroxetine can relieve neuropathic pain. Recently, the role of certain proteins like brain-derived neurotrophic factor (BDNF), GABAA receptor, and K+-Cl- cotransporter 2 (KCC2) transporter in the occurrence of neuropathic pain has been documented. In the current study, the expression of these proteins affected by paroxetine was evaluated.

Methods

Male Wistar rats were allocated into two main groups of pre- and post-injury. Rats in each main group received paroxetine before nerve injury and at day seven after nerve damage till day 14, respectively. The lumbar spinal cord of animals was extracted to assess the expression of target genes and proteins.

Results

In the preventive study, paroxetine decreased BDNF and increased KCC2 and GABAA gene and protein expression, while in the post-injury paradigm, it decreased BDNF and increased KCC2 genes and protein expression. In this regard, an increase in the protein expression of GABAA was observed.

Conclusion

It seems that paroxetine with a change in the expression of three significant proteins involved in neuropathic pain could attenuate this type of chronic pain.

Effect of paroxetine on intestinal motility in the presence of ondansetron

Chemotherapy, radiotherapy, surgery and depression are the conditions that run in parallel fashions. All these conditions cause the release of an increased amount of serotonin in the body. Serotonin acts on these 5HT3 receptors and causes nausea and vomiting. Ondansetron acts by blocking serotonin from acting on the receptors and thus is useful in decreasing episodes of nausea and vomiting but when used concomitantly with SSRIs (selective serotonin reuptake inhibitors) as cancer patient also suffered from depression. This combination tends to decrease the efficacy of ondansetron. The present study was carried out to observe the modulatory role of ondansetron on ileal smooth muscle motility in vitro. Experiments were performed in four groups (n=6) and ileal smooth muscle activity was recorded on the power lab (USA). The effects of increasing concentrations of serotonin, ondansetron and paroxetine alone were observed. In the fourth group effects of paroxetine in the presence of fixed concentration (1ml) of ondansetron (10^-6M) was observed. The maximum response obtained by serotonin served as a control for our study (100%). Paroxetine response on intestinal motility was completely blocked in the presence of ondansetron. Our findings hence, reinforce the hypothesis that paroxetine decreases the antiemetic activity of serotonin antagonist ondansetron, by super sensitization of serotonergic receptors resulting in an increased incidence of nausea and vomiting in cancer patient despite adequate antiemetic prophylaxis.

Serotonin and serotonin reuptake inhibitors alter placental aromatase

Serotonin reuptake inhibitors (SRIs) are currently the main molecules prescribed to pregnant women that suffer from depression. Placental cells are exposed to SRIs via maternal blood, and we have previously shown that SRIs alter feto-placental steroidogenesis in an in vitro co-culture model. More specifically, serotonin (5-HT) regulates the estrogen biosynthetic enzyme aromatase (cytochrome P450 19; CYP19), which is disrupted by fluoxetine and its active metabolite norfluoxetine in BeWo choriocarcinoma cells. Based on molecular simulations, the present study illustrates that the SRIs fluoxetine, norfluoxetine, paroxetine, sertraline, citalopram and venlafaxine exhibit binding affinity for the active-site pocket of CYP19, suggesting potential competitive inhibition. Using BeWo cells and primary villous trophoblast cells isolated from normal term placentas, we compared the effects of the SRIs on CYP19 activity. We observed that paroxetine and sertraline induce aromatase activity in BeWo cells, while venlafaxine, fluoxetine, paroxetine and sertraline decrease aromatase activity in primary villous trophoblast. The effects of paroxetine and sertraline in primary villous trophoblasts were observed at the lower doses tested. We also showed that 5-HT and the 5-HT_2A receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) induced CYP19 activity. An increase in phosphorylation of serine and tyrosine and a decrease in threonine phosphorylation of CYP19 was also associated with DOI treatment. Our results contribute to better understanding how 5-HT and SRIs interact with CYP19 and may affect estrogen production. Moreover, this study suggests that alteration of placental 5-HT levels due to depression and/or SRI treatment during pregnancy may be associated with disruption of placental estrogen production.

N-Methylparoxetine Blocked Autophagic Flux and Induced Apoptosis by Activating ROS-MAPK Pathway in Non-Small Cell Lung Cancer Cells

The main mechanistic function of most chemotherapeutic drugs is mediated by inducing mitochondria-dependent apoptosis. Tumor cells usually respond to upregulate autophagy to eliminate impaired mitochondria for survival. Hypothetically, inhibiting autophagy might promote mitochondria-dependent apoptosis, thus enhancing the efficacy of chemotherapeutic therapies. We previously identified N-methylparoxetine (NMP) as an inducer of mitochondrial fragmentation with subsequent apoptosis in non-small cell lung cancer (NSCLC) cells. We discovered that ROS was accumulated in NMP-treated NSCLC cells, followed by c-Jun N-terminal kinase (JNK) and p38 MAP kinase (p38) activation. This was reversed by the application of a reactive oxygen species (ROS) scavenger, N-acetylcysteine (NAC), leading to a reduction in apoptosis. Our data suggested that NMP induced apoptosis in NSCLC cells by activating mitogen-activated protein kinase (MAPK) pathway. We further speculated that the remarkable increase of ROS in NMP-treated NSCLC cells might result from an inhibition of autophagy. Our current data confirmed that NMP blocked autophagy flux at late stage wherein lysosomal acidification was inhibited. Taken together, this study demonstrated that NMP could exert dual apoptotic functions—mitochondria impairment and, concomitantly, autophagy inhibition. NMP-related excessive ROS accumulation induced apoptosis by activating the MAPK pathway in NSCLC cells.

Enhanced availability of serotonin increases activation of unfatigued muscle but exacerbates central fatigue during prolonged sustained contractions

KEY POINTS

Animal preparations have revealed that moderate synaptic release of serotonin (5-HT) onto motoneurones enhances motor activity via activation of 5-HT2 receptors, whereas intense release of 5-HT causes spillover of 5-HT to extrasynaptic 5-HT1A receptors on the axon initial segment to reduce motoneurone activity. We explored if increasing extracellular concentrations of endogenously released 5-HT (via the selective serotonin reuptake inhibitor paroxetine) influences the ability to perform unfatigued and fatigued maximal voluntary contractions in humans. Following the ingestion of paroxetine, voluntary muscle activation and torque generation increased during brief unfatigued maximal contractions. In contrast, the ability to generate maximal torque with increased 5-HT availability was compromised under fatigued conditions, which was consistent with paroxetine-induced reductions in motoneurone excitability and voluntary muscle activation. This is the first in vivo human study to provide evidence that 5-HT released onto the motoneurones could play a role in central fatigue.

ABSTRACT

Brief stimulation of the raphe-spinal pathway in the turtle spinal cord releases serotonin (5-HT) onto motoneurones to enhance excitability. However, intense release of 5-HT via prolonged stimulation results in 5-HT spillover to the motoneurone axon initial segment to activate inhibitory 5-HT1A receptors, thus providing a potential spinal mechanism for exercise-induced central fatigue. We examined how increased extracellular concentrations of 5-HT affect the ability to perform brief, as well as sustained, maximal voluntary contractions (MVCs) in humans. Paroxetine was used to enhance 5-HT concentrations by reuptake inhibition, and three studies were performed. Study 1 (n = 14) revealed that 5-HT reuptake inhibition caused an ∼4% increase in elbow flexion MVC. However, when maximal contractions were sustained, time-to-task failure was reduced and self-perceived fatigue was higher with enhanced availability of 5-HT. Study 2 (n = 11) used twitch interpolation to reveal that 5-HT-based changes in motor performance had a neural basis. Enhanced 5-HT availability increased voluntary activation for the unfatigued biceps brachii and decreased voluntary activation of the biceps brachii by 2-5% following repeated maximal elbow flexions. The final study (n = 8) investigated whether altered motoneurone excitability may contribute to 5-HT changes in voluntary activation. F-waves of the abductor digiti minimi (ADM) were unaffected by paroxetine for unfatigued muscle and marginally affected following a brief 2-s MVC. However, F-wave area and persistence were significantly decreased following a prolonged 60-s MVC of the ADM. Overall, high serotonergic drive provides a spinal mechanism by which higher concentrations of 5-HT may contribute to central fatigue.

Antidepressants Rescue Stress-Induced Disruption of Synaptic Plasticity via Serotonin Transporter-Independent Inhibition of L-Type Calcium Channels

BACKGROUND

Long-term synaptic plasticity is a basic ability of the brain to dynamically adapt to external stimuli and regulate synaptic strength and ultimately network function. It is dysregulated by behavioral stress in animal models of depression and in humans with major depressive disorder. Antidepressants have been shown to restore disrupted synaptic plasticity in both animal models and humans; however, the underlying mechanism is unclear.

METHODS

We examined modulation of synaptic plasticity by selective serotonin reuptake inhibitors (SSRIs) in hippocampal brain slices from wild-type rats and serotonin transporter (SERT) knockout mice. Recombinant voltage-gated calcium (Ca²⁺) channels in heterologous expression systems were used to determine the modulation of Ca²⁺ channels by SSRIs. We tested the behavioral effects of SSRIs in the chronic behavioral despair model of depression both in the presence and in the absence of SERT.

RESULTS

SSRIs selectively inhibited hippocampal long-term depression. The inhibition of long-term depression by SSRIs was mediated by a direct block of voltage-activated L-type Ca²⁺ channels and was independent of SERT. Furthermore, SSRIs protected both wild-type and SERT knockout mice from behavioral despair induced by chronic stress. Finally, long-term depression was facilitated in animals subjected to the behavioral despair model, which was prevented by SSRI treatment.

CONCLUSIONS

These results showed that antidepressants protected synaptic plasticity and neuronal circuitry from the effects of stress via a modulation of Ca²⁺ channels and synaptic plasticity independent of SERT. Thus, L-type Ca²⁺ channels might constitute an important signaling hub for stress response and for pathophysiology and treatment of depression.

Efficacy and Tolerability of Two Different Kinds of Titration of Paroxetine Hydrocloride Solution: an Observational Study

BACKGROUND

Depressive disorders are expected to be the second highest cause of morbidity in the world until few years. Moreover, patients with depression frequently show many side effects and low compliance to therapy. To find a more tolerated and more efficacy therapy is a growing need.

OBJECTIVE

This observational study investigates the efficacy, safety and tolerability of paroxetine hydrochloride comparing slow versus standard titration in a population affected by Depressive Disoders (according to DSM 5).

METHODS

186 outpatients were assessed throught the following scales: Hamilton Depression Rating Scale (HDRS) for depression and World Health Organization Quality of Life Scale Bref for the perceived quality of life (WHOQOL BREF). Treatment-emerged Adverse Events (TEAEs) were recorded throught self-reports. Statystical analysys was performed by GraphPad Prism Version 5.1.

RESULTS

The efficacy of paroxetine was confirmed in both titrations by the number of clinical remitters (HDRS ≤ 7 at 12 weeks for 53% of the standard titration group and 58% of the slow titration group), without differences. About safety and tolerability there were more frequent TEAEs among the standard titration group (p < 0.01). Comparing WHOQOL BREF between the two groups at the recruitment and at the twelth week emerged a statistically significant difference (p = 0.003), with highest scores reached in slow titration group.

CONCLUSIONS

Although the short observation period is an evident limit, this study is consistent to the literature about the efficacy of both titrations of paroxetine to improve depression and shows promising results about the increased tolerability of paroxetine slow titration.

Sertraline, Paroxetine, and Chlorpromazine Are Rapidly Acting Anthelmintic Drugs Capable of Clinical Repurposing

Parasitic helminths infect over 1 billion people worldwide, while current treatments rely on a limited arsenal of drugs. To expedite drug discovery, we screened a small-molecule library of compounds with histories of use in human clinical trials for anthelmintic activity against the soil nematode Caenorhabditis elegans. From this screen, we found that the neuromodulatory drugs sertraline, paroxetine, and chlorpromazine kill C. elegans at multiple life stages including embryos, developing larvae and gravid adults. These drugs act rapidly to inhibit C. elegans feeding within minutes of exposure. Sertraline, paroxetine, and chlorpromazine also decrease motility of adult Trichuris muris whipworms, prevent hatching and development of Ancylostoma caninum hookworms and kill Schistosoma mansoni flatworms, three widely divergent parasitic helminth species. C. elegans mutants with resistance to known anthelmintic drugs such as ivermectin are equally or more susceptible to these three drugs, suggesting that they may act on novel targets to kill worms. Sertraline, paroxetine, and chlorpromazine have long histories of use clinically as antidepressant or antipsychotic medicines. They may represent new classes of anthelmintic drug that could be used in combination with existing front-line drugs to boost effectiveness of anti-parasite treatment as well as offset the development of parasite drug resistance.

Comprehensive patterns of comorbidity: copd and depression. Aspects of treatment

OBJECTIVE

Introduction: Data on the prevalence of psychopathological disorders in the exacerbation of chronic obstructive pulmonary disease (COPD) are very heterogeneous. COPD and depression have common predisposing factors. The aim: The aim of the research is to conduct a comprehensive assessment of the effect of paroxetine on the level of depressive disorders in the exacerbation of severe degree COPD in women.

PATIENTS AND METHODS

Materials and methods: The study included patients with severe degree COPD and depressive disorder. A step-by-step test, dynamometry of muscular strength of muscle groups and calculation of the percent ratio of muscular strength to mass were performed for all patients, and the strength of the respiratory muscles was measured. To assess the level of depression, the HADS questionnaire and the CES-D self-questionnaire were used. Assessment of the severity of the patient's condition was conducted according to the Hospital Alert and Depression Scale (HADS).

RESULTS

Results: In exacerbation of severe COPD, the level of depression in patients correlates with the severity of the main criteria: FEV1, the 6-minute step test distance, oxygen saturation after the 6-minute step test, expiratory pressure in the oral cavity.

CONCLUSION

Conclusions: Upon the synchronization of the standard therapy, the level of depression in patients with exacerbation of severe COPD effectively decreases. Paroxetine is a valid choice in the comprehensive treatment of COPD. According to the data of evidence-based medicine, the medication demonstrates high efficiency and favorable safety profile, without exerting a negative effect on COPD, which is of key significance in the combined pathology treatment.

Common genes associated with antidepressant response in mouse and man identify key role of glucocorticoid receptor sensitivity

Response to antidepressant treatment in major depressive disorder (MDD) cannot be predicted currently, leading to uncertainty in medication selection, increasing costs, and prolonged suffering for many patients. Despite tremendous efforts in identifying response-associated genes in large genome-wide association studies, the results have been fairly modest, underlining the need to establish conceptually novel strategies. For the identification of transcriptome signatures that can distinguish between treatment responders and nonresponders, we herein submit a novel animal experimental approach focusing on extreme phenotypes. We utilized the large variance in response to antidepressant treatment occurring in DBA/2J mice, enabling sample stratification into subpopulations of good and poor treatment responders to delineate response-associated signature transcript profiles in peripheral blood samples. As a proof of concept, we translated our murine data to the transcriptome data of a clinically relevant human cohort. A cluster of 259 differentially regulated genes was identified when peripheral transcriptome profiles of good and poor treatment responders were compared in the murine model. Differences in expression profiles from baseline to week 12 of the human orthologues selected on the basis of the murine transcript signature allowed prediction of response status with an accuracy of 76% in the patient population. Finally, we show that glucocorticoid receptor (GR)-regulated genes are significantly enriched in this cluster of antidepressant-response genes. Our findings point to the involvement of GR sensitivity as a potential key mechanism shaping response to antidepressant treatment and support the hypothesis that antidepressants could stimulate resilience-promoting molecular mechanisms. Our data highlight the suitability of an appropriate animal experimental approach for the discovery of treatment response-associated pathways across species.

Major depression is the second leading cause of disability worldwide. However, only one-third of patients with depression benefit from the first antidepressant compound they are prescribed. It is a fundamental problem that the outcomes of individual antidepressant treatments are still highly unpredictable. In clinical studies, discovery of biomarkers for antidepressant response is hampered by confounding factors such as the heterogeneity of the disease phenotype and additional environmental factors, e.g., previous life events and different schedules of psychopharmacological treatment, which reduce the power to detect true response biomarkers. To overcome some of these limitations, we have established a conceptually novel approach that allows the selection of extreme phenotypes in an antidepressant-responsive mouse strain. In the first step, we identify signatures in the transcriptome of peripheral blood associated with responses following stratification into good and poor treatment responders. As proof of concept, we translate the murine data to a population of depressed patients. We show that differences in expression profiles from baseline to week 12 of the human orthologues predict response status in patients. We finally provide evidence that sensitivity of the glucocorticoid receptor could be a potential key mechanism shaping response to antidepressant treatment.

In vitro anti-Candida activity of selective serotonin reuptake inhibitors against fluconazole-resistant strains and their activity against biofilm-forming isolates

Recent research has shown broad antifungal activity of the classic antidepressants selective serotonin reuptake inhibitors (SSRIs). This fact, combined with the increased cross-resistance frequency of the genre Candida regarding the main treatment today, fluconazole, requires the development of novel therapeutic strategies. In that context, this study aimed to assess the antifungal potential of fluoxetine, sertraline, and paroxetine against fluconazole-resistant Candida spp. planktonic cells, as well as to assess the mechanism of action and the viability of biofilms treated with fluoxetine. After 24 h, the fluconazole-resistant Candida spp. strains showed minimum inhibitory concentration (MIC) in the ranges of 20-160 μg/mL for fluoxetine, 10-20 μg/mL for sertraline, and 10-100.8 μg/mL for paroxetine by the broth microdilution method (M27-A3). According to our data by flow cytometry, each of the SSRIs cause fungal death after damaging the plasma and mitochondrial membrane, which activates apoptotic signaling pathways and leads to dose-dependant cell viability loss. Regarding biofilm-forming isolates, the fluoxetine reduce mature biofilm of all the species tested. Therefore, it is concluded that SSRIs are capable of inhibit the growth in vitro of Candida spp., both in planktonic form, as biofilm, inducing cellular death by apoptosis.

Ovariectomy changes the response to antidepressant drugs in tail suspension test in mice

Depressive symptoms are very frequent over a lifetime, especially for women. Menopause is a period of higher depressive vulnerability. There are suggestive data that estrogen deficiency may increase the susceptibility for depression. We studied whether a bilateral ovariectomy (OVX) modifies mice behaviors and antidepressant drug effects through tail suspension test (TST). We evaluated behavioral changes at 1 week, 2 weeks, and up to 2 months after OVX. The behavior responses to doxepin, paroxetine, and venlafaxine at 1 week, 2 weeks, and 2 months after OVX were evaluated. No obvious difference was detected on the duration of immobility among control group, sham group, and OVX group in the TST at 1 week and 2 weeks after OVX. But the duration of immobility of OVX group was distinctly longer than that of both control group and sham operation group at 2 months after OVX. At 1 and 2 weeks after OVX, only the antidepressant response to venlafaxine was observed, while response to paroxetine increased 2 months after OVX. Response to antidepressant drugs was strongly modified in OVX mice. The present results suggest that not all antidepressant drugs are appropriate for depression with estrogen deficiency.

Influence of the selective antagonist of the NR2B subunit of the NMDA receptor, traxoprodil, on the antidepressant-like activity of desipramine, paroxetine, milnacipran, and bupropion in mice

Pre-clinical and clinical studies indicated that a blockade of the NMDA receptor complex creates new opportunities for the treatment of affective disorders, including depression. The aim of the present study was to assess the influence of traxoprodil (10 mg/kg) on the activity of desipramine (10 mg/kg), paroxetine (0.5 mg/kg), milnacipran (1.25 mg/kg), and bupropion (10 mg/kg), each at sub-therapeutic doses. Moreover, brain levels of traxoprodil and tested agents were determined using HPLC. The obtained results were used to ascertain the nature of occurring interaction between traxoprodil and studied antidepressants. The experiment was carried out on naïve adult male Albino Swiss mice. Traxoprodil and other tested drugs were administered intraperitoneally. The influence of traxoprodil on the activity of selected antidepressants was evaluated in forced swim test (FST). Locomotor activity was estimated to exclude false positive/negative data. To assess the influence of traxoprodil on the concentration of used antidepressants, their levels were determined in murine brains using HPLC. Results indicated that traxoprodil potentiated activity of all antidepressants examined in FST and the observed effects were not due to the increase in locomotor activity. Only in the case of co-administration of traxoprodil and bupropion, increased bupropion concentrations in brain tissue were observed. All tested agents increased the traxoprodil levels in the brain. Administration of a sub-active dose of traxoprodil with antidepressants from different chemical groups, which act via enhancing monoaminergic transduction, caused the antidepressant-like effect in FST in mice. The interactions of traxoprodil with desipramine, paroxetine, milnacipran, and bupropion occur, at least partially, in the pharmacokinetic phase.

Paroxetine Useful for Palmar–Plantar Hyperhidrosis

Objective:

To report a case of palmar–plantar hyperhidrosis (PPH) In which paroxetine was found to be helpful.

Case Summary:

A 32-year-old man with a history of excessive sweating of the palms and soles since childhood was diagnosed with PPH and was prescribed paroxetine 10 mg/day, which was increased to 20 mg/day. After one month, he experienced a marked reduction in sweating and improvement in socio-occupational functioning, which were sustained during follow-up at 6 months without any emergent adverse effects.

Discussion:

Paroxetine's anticholinergic action may be responsible for its beneficial effect in PPH, as it may override the adrenergic mechanism, which has a minor effect on sweating from eccrine glands. Alternatively, paroxetine's beneficial effect in PPH may be secondary to its antianxiety effect, through central mechanisms.

Conclusions:

Paroxetine may be a useful option in the treatment of PPH.

Effect of antidepressants on spatial memory deficit induced by dizocilpine

Cognitive deficits are a core symptom of schizophrenia. It is controversial whether antidepressants could improve cognitive symptoms in schizophrenia patients. The present study was designed to identify the therapeutic effect of antidepressants on cognitive deficits in schizophrenia. In the present study, adolescent rats were repeatedly exposed to dizocilpine, which can induce cognitive deficits associated with schizophrenia. Then these rats were treated by six antidepressants (fluvoxamine, sertraline, paroxetine, escitalopram, venlafaxine, mirtazapine) or vehicle. The rats in the control group were exposed to vehicle during the study. Lastly, all rats' spatial memory (a major part of cognition) was assessed using the Morris water maze (MWM) test, and the density of hippocampal parvalbumin (PV) interneurons was evaluated to explore possible mechanisms underlying spatial memory change in schizophrenia. The results of the present study supported the hypothesis of a therapeutic effect of fluvoxamine and escitalopram on spatial memory deficit induced by dizocilpine. Additionally, the data of the present study suggested that fluvoxamine and escitalopram remitted hippocampal PV interneuron reduction induced by dizocilpine. The neuroprotective effect of fluvoxamine and escitalopram may partly explain the therapeutic effect of antidepressants on spatial memory deficit in schizophrenia patients.

Time-course of serotonin transporter occupancy by single dose of three SSRIs in human brain: A positron emission tomography study with [(11)C]DASB

Sixteen healthy volunteers were enrolled and divided into four groups according to the single administration of 10mg or 20mg escitalopram, 50mg sertraline, or 20mg paroxetine. Four positron emission tomography scans with [(11)C]DASB were performed on each subject, the first prior to taking the drug, followed by the others at 4, 24, and 48h after. Serotonin transporter occupancies of the drugs at each time point were calculated. All drugs showed maximum occupancy at 4h after dosing and then decreasing occupancies with time. Escitalopram and sertraline showed high occupancies of 69.1-77.9% at 4h, remaining at 52.8-57.8% after 48h. On the other hand, paroxetine showed relatively low occupancy of 44.6%, then decreasing to 10.3% at 48h. Escitalopram (both 10mg and 20mg) and sertraline (50mg) showed high and sustained occupancy. Paroxetine (20mg) showed relatively low and rapidly decreasing occupancy, possibly due to the low plasma concentration by single dosing schedule. Applying the reported concentration of multiple dosing, 20mg paroxetine will induce over 80% occupancy. The present study suggested that these drugs and doses would be sufficient for the treatment of depression.

Differential effects of vilazodone versus citalopram and paroxetine on sexual behaviors and serotonin transporter and receptors in male rats

RATIONALE

Sexual side effects are commonly associated with selective serotonin reuptake inhibitor (SSRI) treatment. Some evidence suggest that activation of 5-HT1A receptors attenuates SSRI-induced sexual dysfunction.

OBJECTIVE

This study in male rats compared the effects of vilazodone, an antidepressant with SSRI and 5-HT1A receptor partial agonist activity, with other prototypical SSRIs (citalopram and paroxetine) on sexual behaviors and 5-HT receptors (5-HT1A and 5-HT2A) and transporter (5-HTT) levels in select forebrain regions of the limbic system using quantitative autoradiography.

METHODS

Rats received vilazodone (1, 3, and 10 mg/kg), citalopram (10 and 30 mg/kg), or paroxetine (10 mg/kg) treatment for 14 days. Sexual behaviors (frequency and latency of mounts, intromissions, and ejaculations) were measured in the presence of an estrous female rat on days 1 (acute), 7 (subchronic), and 14 (chronic).

RESULTS

Vilazodone-treated rats exhibited no sexual dysfunction compared with controls; in contrast, the citalopram- and paroxetine-treated rats exhibited impaired copulatory and ejaculatory behaviors after subchronic and chronic treatments. Chronic vilazodone treatment markedly decreased 5-HT1A receptor levels in cortical and hippocampal regions, while the SSRIs increased levels of this receptor in similar regions. All chronic treatments reduced 5-HTT levels across the forebrain; however, the magnitude of the decrease was considerably smaller for vilazodone than for the SSRIs.

CONCLUSIONS

The current studies showed that chronic treatment with vilazodone, in contrast to citalopram and paroxetine, was not associated with diminished sexual behaviors in male rats, which may be related to the differential effects of vilazodone on 5-HT1A receptor and 5-HTT levels relative to conventional SSRIs.

Paroxetine: An update of response on intestinal motility

OBJECTIVE

To find out the possible effects of paroxetine on gastrointestinal smooth muscles in vitro as they can cause severe nausea and vomiting at the start of therapy which later settles down.

METHODS

Power lab (USA) was used for recording the contractions of ileal smooth muscle of rabbits in response to acetylcholine, serotonin and paroxetine.

RESULTS

The percent responses with acetylcholine, serotonin and paroxetine were 100, 158.7 and 6.45 percent respectively indicating that acetylcholine and serotonin causes an increase in contractility of isolated ileal smooth muscle in comparison to paroxetine which has a depressant effect on motility.

CONCLUSIONS

Inability of paroxetine to enhance the serotonergic transmission in vitro causes a decrease in its qualitative response.