Neonatal fluoxetine exposure modulates serotonergic neurotransmission and disturb inhibitory action of serotonin on food intake

Fluoxetine promotes the recovery of dysphagia and improves nutritional status and neurotrophic status in dysphagia patients after acute ischemic stroke

This study aimed to investigate the effects of fluoxetine on swallowing function, neurotrophic factors, and psychological status in patients with dysphagia after acute ischemic stroke (AIS). A total of 118 patients with dysphagia after AIS who were diagnosed and treated in our hospital from July 2020 to March 2022 were selected as the study objects with 59 cases in each group. Patients in the control group underwent routine treatment and swallowing rehabilitation without fluoxetine. Patients in the study group received routine treatment, swallowing rehabilitation, and fluoxetine treatment. The quality of life was compared according to the Generic Quality of Life Inventory-74 (CQOLI-74). Patients were followed for 90 days, and the grades were compared with the Modified Rankin Scale (mRS). The total effective rate of the study group was 84.75%, which was higher than that of the control group with 62.71% (χ2 = 7.394, P < 0.05). The life quality scores of the two groups were both dramatically elevated compared to those before the treatment, and the study group had a sensibly higher life quality score than the control group (P < 0.05). The proportion of grade 4~5 in the study group was significantly lower than that in the control group (χ2 = 492, P < 0.05). The total incidence of adverse reactions in the control group was 5.08% (3/59), which was significantly lower than that in the study group with 11.86% (7/59) (χ2 = 1.748, P = 0.186). Fluoxetine has a significant effect on the treatment of dysphagia after AIS by enhancing the recovery of dysphagia and promoting the recovery of neurological function.

Serotonergic neuromodulation of synaptic plasticity

Synaptic plasticity constitutes a fundamental process in the reorganization of neural networks that underlie memory, cognition, emotional responses, and behavioral planning. At the core of this phenomenon lie Hebbian mechanisms, wherein frequent synaptic stimulation induces long-term potentiation (LTP), while less activation leads to long-term depression (LTD). The synaptic reorganization of neuronal networks is regulated by serotonin (5-HT), a neuromodulator capable of modify synaptic plasticity to appropriately respond to mental and behavioral states, such as alertness, attention, concentration, motivation, and mood. Lately, understanding the serotonergic Neuromodulation of synaptic plasticity has become imperative for unraveling its impact on cognitive, emotional, and behavioral functions. Through a comparative analysis across three main forebrain structures-the hippocampus, amygdala, and prefrontal cortex, this review discusses the actions of 5-HT on synaptic plasticity, offering insights into its role as a neuromodulator involved in emotional and cognitive functions. By distinguishing between plastic and metaplastic effects, we provide a comprehensive overview about the mechanisms of 5-HT neuromodulation of synaptic plasticity and associated functions across different brain regions.

Fluoxetine alters rat's milk properties causing impact on offspring's development

Fluoxetine is an antidepressant used to treat several conditions including postpartum depression. This disease causes cognitive, emotional, behavioral and physical changes, negatively affecting the mother, child and family life. However, fluoxetine is excreted in breast milk, causing short and long-term effects on children who were exposed to the drug during lactation, so studies that seek to uncover the consequences of these effects are needed. Thus, the aim of this study was to evaluate the effects of fluoxetine on the nutritional characteristics of milk and on growth and neurobehavioral development of the offspring on a rat model. Lactating rats were divided into 4 groups: control group and three experimental groups, which were treated with different doses of fluoxetine (1, 10 and 20 mg/kg) during the lactation. Dams body weight and milk properties were measured, as well as offspring's growth and physical and neurobehavioral development. Results showed that the use of fluoxetine during lactation decreased dam's body weight and alters milk's properties, leading to a decrease in offspring's growth until adulthood. Therefore, the use of fluoxetine during lactation needs to be cautiously evaluated, with the benefits to the mothers and the associated risk to the offspring carefully balance.

Perinatal serotonergic manipulation shapes anhedonic and cognitive behaviors in a sex- and age-dependent manner: Identification of related biological functions at central and peripheral level

Poor knowledge about psychiatric disorders often results in similar diagnoses for patients with different symptoms, thus limiting the effectiveness of the available medications. As suggested by several lines of evidence, to improve these shortcomings, it is essential to identify biomarkers associated with specific symptoms and to stratify patients into more homogeneous populations taking a further step toward personalized medicine. Here, we aimed to associate specific behavioral phenotypes with specific molecular alterations by employing an animal model based on the pharmacological manipulation of the serotonergic system, which mimics a condition of vulnerability to develop psychiatric disorders. In particular, we treated female and male rats with fluoxetine (FLX 15 mg/kg dissolved in drinking water) during prenatal or early postnatal life, and we evaluated different pathological-like phenotypes (cognitive deficit, anhedonia, and anxiety) by exposing the rats to a battery of behavioral tests during adolescence and adulthood. In addition, we carried out molecular analyses on specific brain areas and in the blood. Our results showed that perinatal FLX administration determined age- and sex-dependent effects, with males being more sensitive to prenatal manipulation and manifesting anhedonic-like behavior and females to early postnatal exposure, exhibiting cognitive deficits and a less anxious phenotype. Furthermore, we identified, peripherally and centrally, biological functions altered by perinatal serotonin modulation regardless of the timing of exposure and sex, and other pathways specific for the pathological-like phenotypes. The results presented here provide new insights into potential biomarkers associated with specific behavioral phenotypes that may be useful for broadening knowledge about psychiatric conditions.

Toxicological Study on Chiral Fluoxetine Exposure to Adult Zebrafish (Danio rerio): Enantioselective and Sexual Mechanism on Disruption of the Brain Serotonergic System

The increasing number of people with depression worldwide has led to concerns regarding antidepressant contamination in aquatic environments, which could have the risk of negative effects on aquatic organisms. Chirality increases its toxicity potentials. Accordingly, we investigated the negative effects of racemic (rac-), R-, and S-FX at environmental levels (100 ng/L) on the brain serotonergic system in zebrafish (Danio rerio) for 42 days. Additionally, we measured the whole-body concentrations of FX and norfluoxetine (NFX). We found that S-FX exposure disrupted the brain serotonergic system more severely than rac- and R-FX exposure. The mechanism underlying this disruption induced by S-FX was sex-specific, with female zebrafish showing disruption of the serotonin (5-HT) release process but male zebrafish showing disruption of the 5-HT synthesis process. In addition, enantioselective enrichment and biotransformation (R-FX to R-NFX and S-FX to S-NFX) occurred in zebrafish. Sex-specific accumulation was also observed, with higher concentrations in females. Our study provides evidence for enantiomer- and sex-specific effects of FX exposure at biologically relevant concentrations. More broadly, our study demonstrated that SSRI antidepressants, such as FX, can affect aquatic life by causing important shifts in not only their active sites of the serotonin transporter.

Repeated fluoxetine treatment induces transient and long-term astrocytic plasticity in the medial prefrontal cortex of normal adult rats

Fluoxetine (Flx)-induced neuronal plasticity plays an important role in the effective treatment of depression and mood disorders. It is less understood whether repeated Flx treatment induces astrocytic plasticity that outlasts the presence of the drug in the body. We showed previously that Flx-induced neuronal plasticity in the medial prefrontal cortex (mPFC) persisted up to 20 days after the treatment. In this study, adult rats were subjected to a 15-day repeated Flx treatment at a daily dose of 20 mg/kg body weight. Astrocytic metabolites and markers were assessed in the mPFC at day 1 (d1) and day 20 (d20) after the treatment. Significant transient reductions in the concentrations of astrocytic metabolites taurine and myo-inositol and the expressions of glial fibrillary acidic protein (GFAP) and aquaporin-4 (AQP4) were observed in the mPFC of Flx-treated rats at d1, which recovered to the control levels at d20. Further, Flx treatment resulted in long-lasting changes in Kir4.1 expression in the mPFC, which remained downregulated at d20. The expression of 5-HT_1A receptor in the mPFC of Flx-treated rats was downregulated at d1 but became upregulated at d20. In summary, repeated Flx treatment induces both transient and long-term astrocytic plasticity in the mPFC of adult rats. The changes observed at d1 are consistent with disturbed water homeostasis and astrocytic de-maturation in the mPFC. The persistent changes in the expressions of Kir4.1 and 5-HT_1A at d20, presumably of the astrocytic origin, might have contributed to the long-term neurotrophic effects of repeated Flx treatment in the mPFC.

Perinatal exposure to a high-fat diet alters proopiomelanocortin, neuropeptide Y and dopaminergic receptors gene expression and the food preference in offspring adult rats

Exposure to the hight-fat diet may alter the control of food intake promoting hyperphagia and obesity. The objective of this study was to investigate the effects of this diet on dopamine receptors (drd1 and drd2), proopiomelanocortin (pomc), neuropeptideY (npy) genes expression, and preference food in adult rats. Wistar female rats were fed a hight-fat or control diet during pregnancy and lactation. The offspring were allocated into groups: Lactation - Control (C) and High-fat (H). Post-weaning - Control Control (CC), offspring of mothers C, fed a control diet after weaning; Control Hight-fat (CH), offspring of mothers C, fed a hight-fat diet after weaning; Hight-fat Control (HC), offspring of mothers H, fed with control diet after weaning; and Hight-fat Hight-fat (HH), offspring of mothers H, fed a H diet after weaning. The groups CH and HH presented greater expression of drd1 in comparison to the CC. The drd2 of CH and HC presented higher gene expression than did CC. HH presented higher pomc expression in comparison to the other groups. HC also presented greater expression in comparison to CH. The npy of HH presented greater expression in relation to CH and HC. HH and HC have had a higher preference for a high-fat diet at 102º life's day. The high-fat diet altered the gene expression of the drd1, drd2, pomc and npy, and influencing the food preference for high-fat diet.

Serotonin stimulated parathyroid hormone related protein induction in the mammary epithelia by transglutaminase-dependent serotonylation

Mammary-derived serotonin has been implicated in breast-to-bone communication during lactation by increasing parathyroid hormone related-protein (PTHrP) in the mammary gland. It is well established that PTHrP acts on the bone to liberate calcium for milk synthesis during lactation; however, the mechanism of serotonin’s regulation of PTHrP has not been fully elucidated. Recently, serotonylation has been shown to be involved in a variety of physiological processes mediated by serotonin. Therefore, we investigated whether serotonylation is involved in serotonin’s regulation of PTHrP in the mammary gland using lactogenically differentiated mouse mammary epithelial cells. We investigated the effect of increased intracellular serotonin using the antidepressant fluoxetine or 5-hydroxytryptophan (serotonin precursor), with or without transglutaminase inhibition and the corresponding action on PTHrP induction and activity. Treatment with fluoxetine or 5-hydroxytryptophan significantly increased intracellular serotonin concentrations and subsequently increased PTHrP gene expression, which was reduced with transglutaminase inhibition. Furthermore, we determined that transglutaminase activity is increased with lactogenic differentiation and 5-hydroxytryptophan or fluoxetine treatment. We investigated whether RhoA, Rac1, and Rab4 were potential serotonylation target proteins. We speculate that RhoA is potentially a serotonylation target protein. Our data suggest that serotonin regulates PTHrP induction in part through the process of serotonylation under lactogenic conditions in mouse mammary epithelial cells.

Effect of Electroacupuncture on Reuptake of Serotonin via miRNA-16 Expression in a Rat Model of Depression

The current study aimed to investigate the effects and mechanisms of electroacupuncture (EA) treatment applied to Bai hui (GV20) and Yin tang (GV29) acupoints (1 mA, 2 Hz, continuous wave, 20 minutes) for 28 days in a rat model of chronic unpredictable mild stress (CUMS) on reuptake of serotonin (5-hydroxytryptamine (5-HT)) and miRNA-16 levels in the hippocampus and serum. Rats were housed in individual cages, and CUMS was used to establish a rat model of depression. After EA treatment for 4 weeks, behavioral changes and indices including 5-HT transporter (SERT), 5-HT, and miRNA-16 levels in the hippocampus and serum were examined. The EA treatment significantly improved base levels of sucrose preference and exploratory behavior and significantly decreased SERT protein and mRNA expression in the hippocampus of depressed rats. Significantly increased 5-HT levels were observed, and miRNA-16 levels were significantly decreased in the hippocampus and serum of depressed rats. In conclusion, the antidepressant effects of EA treatment may be affected via inhibition of 5-HT reuptake, upregulation of 5-HT levels, and inhibition of miRNA-16 expression in the hippocampus and serum.

Exposure of dams to fluoxetine during lactation disturbs maternal behavior but had no effect on the offspring behavior

Fluoxetine is one of the most commonly prescribed drugs for treatment of depression during pregnancy as well as postpartum. Nevertheless, fluoxetine can cross the placental barrier and/or be secreted through breastmilk and questions remain unanswered regarding safety of the unborn and/or nursing infant. Passive administration of antidepressants to infants can cause neurological developmental delay and/or dysfunction. To date, there are limited studies on neurobehavioral effects due to passive administration of fluoxetine in nursing animals. Thus, the aim of the present study was to evaluate the effects of fluoxetine exposure on the behavior of lactating dams and their offspring. Dams received either 1, 10 or 20 mg/kg fluoxetine via oral gavage (controls received water alone) from lactating day (LD) 1 to 21. Maternal behavioral studies were conducted from LD5 to LD7 and offspring studies were conducted from LD2 to LD60. Results showed dysfunction in maternal behavior, both in direct and indirect behavior, but there were no differences and/or deficiencies observed in offspring behavior. These data suggest that the impairment of dams maternal behavior combined with the amount of fluoxetine that the offspring received through breast milk during lactation did not alter their social behavior in infancy and/or adulthood, suggesting no neurodevelopmental damage associated with maternal use of fluoxetine. This study contributes to the field of human psychiatric diseases by further elucidating the effects of antidepressant medications on the health of mothers as well as children who were passively exposed to drug treatment.

Serotonin transporter inhibition during neonatal period induces sex-dependent effects on mitochondrial bioenergetics in the rat brainstem

The serotonin reuptake is mainly regulated by the serotonin transporters (SERTs), which are abundantly found in the raphe nuclei, located in the brainstem. Previous studies have shown that dysfunction in the SERT has been associated with several disorders, including depression and cardiovascular diseases. In this manuscript, we aimed to investigate how gender and the treatment with a serotonin selective reuptake inhibitor (SSRI) could affect mitochondrial bioenergetics and oxidative stress in the brainstem of male and female rats. Fluoxetine, our chosen SSRI, was used during the neonatal period (i.e., from postnatal Day 1 to postnatal Day 21-PND1 to PND21) in both male and female animals. Thereafter, experiments were conducted in adult rats (60 days old). Our results demonstrate that, during lactation, fluoxetine treatment modulates the mitochondrial bioenergetics in a sex-dependent manner, such as improving male mitochondrial function and female antioxidant capacity.