Sex-dependent effects of chronic fluoxetine exposure during adolescence on passive avoidance memory, nociception, and prefrontal brain-derived neurotrophic factor mRNA expression

Cardiac and hepatic side effects of fluoxetine in male and female adolescent rats

BACKGROUND

Fluoxetine (FLX) is widely prescribed as an antidepressant medicine in the juvenile population.

OBJECTIVES

Although some adverse effects of FLX have been reported in adults, the present study aimed to investigate the side effects of FLX treatment during adolescence on the cardiac and hepatic systems.

METHODS

Male and female rats were gavaged with FLX (5 mg/kg/day) on postnatal days (PND) 21 to PND 60. Following treatment, blood samples were collected and hepatic enzymes were evaluated. The specimens of the liver and heart of animals were subjected to histopathological assessment.

RESULTS

Fluoxetine significantly raised serum alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in males, whereas the aspartate aminotransferase (AST) level increased in both male and female animals. In the histopathological study, hepatic plates were more seriously affected, and the sinusoids were irregular in adolescent male rats. Degenerative changes were observed especially in the first and second hepatic zones of FLX-treated male rats. Signs of inflammation and accumulation of lymphoid groups were frequently observed in the portal triad of the hepatic lobules. These alterations were more severe in male livers. Minimum or nearly normal changes were observed in female liver slides. In addition, the histological assessment indicated that treatment with FLX during adolescence also increased the heart's weight and the wall thickness of the right and left ventricles (hypertrophy) in male and especially female animals.

CONCLUSION

Our findings may provide new insights into the cardiac and hepatic adverse effects of FLX.

Pain sensitivity as a state marker and predictor for adolescent non-suicidal self-injury

BACKGROUND

The pain analgesia hypothesis suggests that reduced pain sensitivity (PS) is a specific risk factor for the engagement in non-suicidal self-injury (NSSI). Consistent with this, several studies found reduced PS in adults as well as adolescents with NSSI. Cross-sectional studies in adults with borderline personality disorder (BPD) suggest that PS may (partially) normalize after remission or reduction of BPD symptoms. The objective of the present study was to investigate the development of PS over 1 year in a sample of adolescents with NSSI and to investigate whether PS at baseline predicts longitudinal change in NSSI.

METHODS

N = 66 adolescents who underwent specialized treatment for NSSI disorder participated in baseline and 1-year follow-up assessments, including heat pain stimulation for the measurement of pain threshold and tolerance. Associations between PS and NSSI as well as BPD and depressive symptoms were examined using negative binomial, logistic, and linear regression analyses.

RESULTS

We found that a decrease in pain threshold over time was associated with reduced NSSI (incident rate ratio = 2.04, p = 0.047) and that higher pain tolerance at baseline predicted lower probability for NSSI (odds ratio = 0.42, p = 0.016) 1 year later. However, the latter effect did not survive Holm correction (p = 0.059). No associations between PS and BPD or depressive symptoms were observed.

CONCLUSION

Our findings suggest that pain threshold might normalize with a decrease in NSSI frequency and could thus serve as a state marker for NSSI.

NXP032 ameliorates cognitive impairment by alleviating the neurovascular aging process in aged mouse brain

Vascular aging is well known to be associated with the breakdown of the neurovascular unit (NVU), which is essential for maintaining brain homeostasis and linked to higher cognitive dysfunction. Oxidative stress is believed to be a significant cause of the vascular aging process. Vitamin C is easily oxidized under physiological conditions, so it loses its potent antioxidant activity. We developed a DNA aptamer that enhances the function of vitamin C. NXP032 is the binding form of the aptamer and vitamin C. In this study, we investigated the effect of NXP032 on neurovascular stabilization through the changes of PECAM-1, PDGFR-β, ZO-1, laminin, and glial cells involved in maintaining the integrity of the blood-brain barrier (BBB) in aged mice. NXP032 was orally administered daily for 8 weeks. Compared to young mice and NXP032-treated mice, 20-month-old mice displayed cognitive impairments in Y-maze and passive avoidance tests. NXP032 treatment contributed to reducing the BBB damage by attenuating the fragmentation of microvessels and reducing PDGFR-β, ZO-1, and laminin expression, thereby mitigating astrocytes and microglia activation during normal aging. Based on the results, we suggest that NXP032 reduces vascular aging and may be a novel intervention for aging-induced cognitive impairment.

5-HT attenuates chronic stress-induced cognitive impairment in mice through intestinal flora disruption

BACKGROUND

The microbiota-gut-brain axis plays an important role in the development of depression. The aim of this study was to investigate the effects of 5-HT on cognitive function, learning and memory induced by chronic unforeseeable mild stress stimulation (CUMS) in female mice. CUMS mice and TPH2 KO mice were used in the study. Lactococcus lactis E001-B-8 fungus powder was orally administered to mice with CUMS.

METHODS

We used the open field test, Morris water maze, tail suspension test and sucrose preference test to examine learning-related behaviours. In addition, AB-PAS staining, immunofluorescence, ELISA, qPCR, Western blotting and microbial sequencing were employed to address our hypotheses.

RESULTS

The effect of CUMS was more obvious in female mice than in male mice. Compared with female CUMS mice, extracellular serotonin levels in TPH2 KO CUMS mice were significantly reduced, and cognitive dysfunction was aggravated. Increased hippocampal autophagy levels, decreased neurotransmitter levels, reduced oxidative stress damage, increased neuroinflammatory responses and disrupted gut flora were observed. Moreover, L. lactis E001-B-8 significantly improved the cognitive behaviour of mice.

CONCLUSIONS

These results strongly suggest that L. lactis E001-B-8 but not FLX can alleviate rodent depressive and anxiety-like behaviours in response to CUMS, which is associated with the improvement of 5-HT metabolism and modulation of the gut microbiome composition.

Effects of chronic fluoxetine treatment on anxiety- and depressive-like behaviors in adolescent rodents - systematic review and meta-analysis

Background

Drugs prescribed for psychiatric disorders in adolescence should be studied very extensively since they can affect developing and thus highly plastic brain differently than they affect the adult brain. Therefore, we aimed to summarize animal studies reporting the behavioral consequences of chronic exposure to the most widely prescribed antidepressant drug among adolescents i.e., fluoxetine.

Methods

Electronic databases (Medline via Pubmed, Web of Science Core Collection, ScienceDirect) were systematically searched until April 12, 2022, for published, peer-reviewed, controlled trials concerning the effects of chronic fluoxetine administration vs. vehicle on anxiety and depression measures in naïve and stress-exposed adolescent rodents. All of the relevant studies were selected and critically appraised, and a meta-analysis of eligible studies was performed.

Results

A total of 18 studies were included in the meta-analysis. In naïve animals, chronic adolescent fluoxetine administration showed dose-related anxiogenic-like effects, measured as a reduction in time spent in the open arms of the elevated plus maze. No significant effects of chronic adolescent fluoxetine on depression-like behavior were reported in naïve animals, while in stress-exposed rodents chronic adolescent fluoxetine significantly decreased immobility time in the forced swim test compared to vehicle.

Conclusions

These results suggest that although chronic fluoxetine treatment proves positive effects in animal models of depression, it may simultaneously increase anxiety in adolescent animals in a dose-related manner. Although the clinical implications of the data should be interpreted with extreme caution, adolescent patients under fluoxetine treatment should be closely monitored.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00420-w.

Modulating role of serotonergic signaling in sleep and memory

Serotonin is an important neurotransmitter with various receptors and wide-range effects on physiological processes and cognitive functions including sleep, learning, and memory. In this review study, we aimed to discuss the role of serotonergic receptors in modulating sleep-wake cycle, and learning and memory function. Furthermore, we mentioned to sleep deprivation, its effects on memory function, and the potential interaction with serotonin. Although there are thousands of research articles focusing on the relationship between sleep and serotonin; however, the pattern of serotonergic function in sleep deprivation is inconsistent and it seems that serotonin has not a certain role in the effects of sleep deprivation on memory function. Also, we found that the injection type of serotonergic agents (systemic or local), the doses of these drugs (dose-dependent effects), and up- or down-regulation of serotonergic receptors during training with various memory tasks are important issues that can be involved in the effects of serotonergic signaling on sleep-wake cycle, memory function, and sleep deprivation-induced memory impairments. This comprehensive review was conducted in the PubMed, Scopus, and ScienceDirect databases in June and July 2021, by searching keywords sleep, sleep deprivation, memory, and serotonin.

Estrogen receptor agonists induce anti‑edema effects by altering α and β estrogen receptor gene expression

The present study aimed to examine whether the attenuation of estrogen receptor expression is prevented by propyl pyrazole triol (PPT), an agonist for estrogen receptor α (ERα) or and diarypropiolnitrile (DPN), an agonist for estrogen receptor β (ERβ) after traumatic brain injury (TBI). The tests performed on ovariectomized female Wistar rats included sham group, vehicle group, and treated groups: PPT, DPN, and PPT+DPN 30 minutes after TBI. Blood‑brain barrier (BBB) disruption and brain water content were estimated. RT‑PCR and\r\nwestern blotting were utilized to evaluate ESR1 and ESR2 gene and protein expression. The data indicated that PPT, DPN, and PPT+DPN attenuated TBI‑induced brain edema. Also, BBB disruption after TBI was prevented in PPT, DPN, and PPT+DPN‑treated TBI animals. Estrogen agonist‑treated animals showed a significant elevation in Esr1 mRNA and protein expression levels in the brain tissue of TBI rats. In addition, the data indicated a significant elevation of Esr2 mRNA and protein expression levels in the brain tissue of estrogen agonist‑treated TBI rats. The data shows that both ESR1 and ESR2 agonists can enhance ER mRNA and protein levels in TBI animals' brain. It appears that this effect contributes to the neuroprotective function of ER agonists.

Short communication: Ex-vivo effects of fluoxetine on production of biomarkers for inflammation and neurodevelopment by the placenta

Fluoxetine is commonly prescribed during pregnancy but developmental exposure to the drug, like infection, is associated with sex-specific behavioral changes in the offspring. We evaluated the effects of Fluoxetine on production of biomarkers for inflammation (pro/anti-inflammatory cytokines) and neurodevelopment (Brain-Derived Neurotrophic Factor, BDNF) in the presence and absence of infection in female and male placenta explant cultures. In addition to minor anti-inflammatory effects of the drug, Fluoxetine had significant sex- and infection-dependent effects on BDNF production. Further studies are needed to determine the extent to which these observed changes occur in vivo and their impact on pregnancy and neurodevelopmental outcomes.

Serotonin depletion during the postnatal developmental period causes behavioral and cognitive alterations and decreases BDNF level in the brain of rats

A survey of the literature indicates that the developmental disruptions in serotonin (5-HT) levels can influence the brain development and the function. To the best of our knowledge, so far, there are a few studies about the effects of developmental period 5-HT depletion on cognition and behavior of adult male and female rats. Therefore, in the present study, we examined the effects of postnatal days (PND 10-20) administration of para-chlorophenylalanine (PCPA, 100 mg/kg, s.c) a 5-HT synthesis inhibitor, on anxiety-related behaviors, pain sensitivity, short-term recognition memory, and hippocampal and prefrontal cortex (PFC) brain-derived neurotrophic factor (BDNF) mRNA expression in adult male and female rats. Novel object recognition memory (NORM) and behavioral parameters (anxiety-like behaviors and pain sensitivity) were evaluated in early adulthood and after that, the hippocampi and PFC of the rat's brain were removed for the determination of BDNF mRNA expression. Our results indicated that the postnatal period administration of PCPA impaired short-term NORM. The postnatal developmental period treatment with PCPA also increased anxiety-like behaviors in the open field and elevated plus maze (EPM) tests. Postnatal PCPA treatment increased pain sensitivity in the hot plate test in both male and female rats, especially in female animals. In addition, postnatal days serotonin depletion decreased BDNF level in the hippocampus and PFC of both male and female rats. These findings demonstrate that serotonin plays the main role in neurodevelopment, cognitive functions, and behavior. Therefore, serotonergic system dysregulation during the developmental periods may have more adverse influences on the brain development of rats.

Alterations in the behavior, cognitive function, and BDNF level in adult male rats following neonatal blockade of GABA-A receptors

Gamma-aminobutyric acid (GABA) is an important inhibitory neurotransmitter in the mature brain. At an early developmental period, it acts in an excitatory manner that influences many processes of proliferation, migration, and differentiation of the neurons. Previous evidence indicated that manipulation of the GABAergic system function by activation or blockade of its receptors during developmental periods leads to behavioral and cognitive abnormality in adulthood. Therefore, we examined the effects of neonatal blockade of GABA-A receptors by bicuculline on behavior, cognitive function, and hippocampal and prefrontal cortex (PFC) brain-derived neurotrophic factors level (BDNF) in adulthood. As a result, neonatal rats were treated with either bicuculline (75,150, and 300 μg/kg) or DMSO on postnatal days 7,9, and 11. These groups underwent the behavioral (open field, elevated plus maze, and hot plate) and learning and memory (passive avoidance learning and memory) tests in postnatal days (PNDs) 61-70. After the ending of the behavioral tests, the rats were sacrificed under deep anesthesia and the hippocampi and prefrontal cortex (PFC) of the brain were removed for assessing the BDNF mRNA expression. Our results indicated that neonatal administration of bicuculline at the highest dose increased passive avoidance memory and hippocampal BDNF level. Meanwhile, this drug at a low dose impaired this type of memory and increased PFC BDNF level. Besides, treatment with bicuculline during postnatal days increased anxiety and pain sensitivity in a dose-dependent manner. Taken together, these findings confirmed the notion that GABA-A receptors during the developmental period are important for programming neurobehavioral phenotypes in adult life.

Effects of adolescent administration of fluoxetine on novel object recognition memory, anxiety-like behaviors, and hippocampal brain-derived neurotrophic factor level

AIMS

Fluoxetine (FLX) is a common selective serotonin reuptake inhibitor, which is used in adolescents with psychiatric disorders. Controversial results have been obtained in different studies about the effects of FLX on cognitive functions. The present study was designed to examine the effects of chronic FLX exposure during adolescence on cognitive function, anxiety-like behaviors, and hippocampal brain-derived neurotrophic factor (BDNF) mRNA expression among adult male and female rats.

MAIN METHODS

The sex-dependent effects of FLX chronic administration during adolescence (5 mg/kg/day, gavage) on short-term novel object recognition memory (NORM), anxiety-like behaviors, and BDNF mRNA expression in the hippocampus were examined. NORM and anxiety-like behaviors were assessed by novel object recognition, open field, and elevated plus-maze (EPM) tests, respectively. The expression of BDNF mRNA was also evaluated by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR).

KEY FINDINGS

The present findings revealed the dysfunction of short-term NORM among the adolescent male and female rats exposed to FLX, while the mRNA expression of BDNF was significantly higher among the males. Moreover, adolescent FLX administration had different effects on the anxiety-like behaviors of the male and female rats. Adolescent FLX treatment also decreased the body weight of the male animals.

SIGNIFICANCE

In conclusion, adolescent FLX treatment impairs cognitive functions in both sexes and increases BDNF mRNA expression in the hippocampus of the male animals. FLX administration during adolescence has sex-dependent effects on anxiety-like behaviors. These findings indicate that the impairment of cognitive functions can occur following the adolescent manipulation of the serotonergic system. Therefore, the side effects of chronic FLX administration during adolescence should be more considered.