Effects of reboxetine and citalopram pretreatment on changes in cocaine and amphetamine regulated transcript (CART) expression in rat brain induced by the forced swimming test

Anxiolytic-Like and Antidepressant-Like Effects of Resveratrol in Streptozotocin-Induced Diabetic Rats

Introduction

Diabetes is associated with anxiety and depression. Resveratrol, one of the most potent natural polyphenols with antioxidant properties, has been demonstrated to have benefits against diabetes. In the current study, we investigated the effects of resveratrol on depression and anxiety-like behaviors in diabetic rats.

Methods

Adult male Wistar albino rats were assigned for control and diabetic groups, and these groups were divided into four subgroups as follows: Saline-treated, DMSO-treated, resveratrol-treated and imipramine-treated animals (n=10). Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ) (50 mg/kg), and 2 days after the STZ injection the rats having hyperglycemia (>300 mg/dl) were assigned to be diabetic. Rats in treatment groups were injected intraperitoneally with resveratrol (20 mg/kg) and imipramine (10 mg/kg) for 4 weeks. After 4-week-treatment period, tail suspension test (TST), forced swimming test (FST), elevated plus maze test (EPM) and locomotor activity test were performed. Blood samples were collected to estimate serum superoxide dismutase (SOD) and NADPH oxidase (Nox) levels.

Results

Diabetic rats displayed depressive-like behaviors in the FST and TST, and anxiety-like behaviors in the EPM. Resveratrol and imipramine decreased anxiety-like and depressive-like behaviors without affecting locomotor activity in diabetic rats. A significant reduction in SOD levels and a marked increase in Nox levels were observed in diabetic rats. Resveratrol treatment normalized these levels, while imipramine did not affect neither SOD nor Nox levels.

Conclusion

This study indicates that chronic resveratrol treatment may able to treat comorbid anxiety-and depressive-like behaviors in diabetes through inhibition of oxidative stress.

Low cocaine- and amphetamine-regulated transcript (CART) peptide levels in human cerebrospinal fluid of major depressive disorder (MDD) patients

BACKGROUND

Cocaine- and amphetamine-regulated transcript (CART) peptide is a candidate neuropeptide as a biomarker for major depressive disorder (MDD) because of its effects on emotion and distribution covering brain areas involved in the pathophysiology of MDD symptoms. However, it is unknown whether CART peptide levels are altered in the cerebrospinal fluid (CSF) of patients with MDD patients and are correlated with MDD symptoms.

METHODS

Subjects were 24 patients with MDD and 25 healthy controls matched for age, gender and ethnicity (Japanese). We measured CSF CART levels by a commercially available immunoassay kit and analyzed the relationships of the levels with antidepressant dose and symptoms assessed with the 21 item Hamilton Depression Rating Scale (HAMD-21).

RESULTS

CSF CART levels were significantly decreased in the patients than in the controls (p < 0.05). In MDD patient group, the CART levels had a negative correlation with antidepressant dose (imipramine-equivalent dose) (ρ = -0.55, p < 0.01) and significantly decreased in antidepressant-treated group (AD-treated group) compared to controls (p < 0.05). CSF CART levels showed significant negative correlations with psychomotor retardation, somatic anxiety, and general somatic symptoms (all p < 0.05) and a positive correlation with obsessive and compulsive symptoms (p < 0.05).

LIMITATIONS

In our analysis, all classes of antidepressants were combined together and the effects of medication use in a longitudinal manner did not confirm.

CONCLUSIONS

We report for the first time that CSF CART peptide levels are reduced in patients with MDD compared with healthy controls. The CART levels showed negative correlations with antidepressant dose and some symptoms, supporting the possibility that CART peptide is involved in the development of depressive symptoms.

Antidepressant-like activity of methyl jasmonate involves modulation of monoaminergic pathways in mice

PURPOSE

The efficacy of current antidepressant drugs has been compromised by adverse effects, low remission and delay onset of action necessitating the search for alternative agents. Methyl jasmonate (MJ), a bioactive compound isolated from Jasminum grandiflorum has been shown to demonstrate antidepressant activity but its mechanism of action remains unknown. Thus, the role of monoaminergic systems in the antidepression-like activity of MJ was investigated in this study.

MATERIALS AND METHODS

Mice were given i.p. injection of MJ (5, 10 and 20mg/kg), imipramine (10mg/kg) and vehicle (10mL/kg) 30min before the forced swim test (FST) and tail suspension test (TST) were carried out. The involvement of monoaminergic systems in the anti-depressant-like effect of MJ (20mg/kg) was evaluated using p-chlorophenylalanine (pCPA), metergoline, yohimbine, prazosin, sulpiride and haloperidol in the TST.

RESULTS

MJ significantly decrease the duration of immobility in the FST and TST relative to control suggesting antidepressant-like property. However, pretreatment with yohimbine (1mg/kg, i.p., an α₂-adrenergic receptor antagonist) or prazosin (62.5μg/kg, i.p., an α₁-adrenoceptor antagonist) attenuated the antidepressant-like activity of MJ. Also, pCPA; an inhibitor of serotonin biosynthesis (100mg/kg, i.p) or metergoline (4mg/kg, i.p., 5-HT₂ receptor antagonist) reversed the anti-immobility effect of MJ. Sulpiride (50mg/kg, i.p., a D₂ receptor antagonist) or haloperidol (0.2mg/kg, i.p., a dopamine receptor antagonist) reversed the anti-immobility effect of MJ.

CONCLUSION

The results of this study suggest that serotonergic, noradrenergic and dopaminergic systems may play a role in the antidepressant-like activity of MJ.

Rescue of glutamate transport in the lateral habenula alleviates depression- and anxiety-like behaviors in ethanol-withdrawn rats

Alcoholism and psychiatric disorders like depression and anxiety are often comorbid. Although the mechanisms underlying this comorbidity are unclear, emerging evidence suggests that maladaptation of the glial glutamate transporter GLT-1 may play a role. Findings from animal and human studies have linked aversive states, including those related to drugs of abuse and depression, to aberrant activity in the lateral habenula (LHb). The relationship between GLT-1 maladaptation, LHb activity, and abnormal behaviors related to alcohol withdrawal, however, remains unknown. Here we show that dihydrokainic acid (DHK), a GLT-1 blocker, potentiated glutamatergic transmission to LHb neurons in slices from ethanol naïve rats; this potentiation, though, was not observed in slices from rats withdrawn from repeated in vivo ethanol administration, suggesting reduced GLT-1 function. Furthermore, GLT-1 protein expression was reduced in the LHb of withdrawn rats. This reduction was restored by systemic administration of ceftriaxone, a β-lactam antibiotic known to increase GLT-1 expression. Systemic ceftriaxone treatment also normalized the hyperactivity of LHb neurons in slices from withdrawn rats, which was reversed by bath-applied DHK. Finally, systemic administration of ceftriaxone alleviated depression- and anxiety-like behaviors, which was fully blocked by intra-LHb administrations of DHK, suggesting that GLT-1's function in the LHb is critical. These findings highlight the significant role of LHb astrocytic GLT-1 in the hyperactivity of LHb neurons, and in depressive- and anxiety-like behaviors during ethanol withdrawal. Thus, GLT-1 in the LHb could serve as a therapeutic target for psychiatric disorders comorbid with ethanol withdrawal.

Methyl jasmonate attenuated lipopolysaccharide-induced depressive-like behaviour in mice

Depression is a recurrent neuropsychiatric disorder that affects millions of individuals worldwide and impact negatively on the patients' social functions and quality of life. Studies have shown that i.p injection of lipopolysaccharide (LPS) induces depressive-like behavior in rodents via induction of oxidative stress and neuroinflammation. Methyl jasmonate (MJ), an isolated compound from jasmine plant has gained reputation in aromatherapy for treatment of depression, nervousness and memory deficits. This study was designed to evaluate the effects of MJ on LPS-induced depressive-like behavior in mice. Mice were given MJ (5-20 mg/kg), imipramine (10 mg/kg) or vehicle (10 mL/kg) intraperitoneally for 7 consecutive days. On day 7, treatment was carried out 30 min prior to i.p injection of LPS (830 μg/kg). Twenty four hours after LPS administration, tail suspension, forced swim and sucrose preference tests were carried out. Thereafter, serum corticosterone levels were determined using ELISA. The levels of malondialdehyde (MDA), glutathione (GSH) and tumor necrosis factor-alpha (TNF-α) were determined in brain tissue homogenates. LPS significantly increased immobility time in the tail suspension and forced swim tests when compared with vehicle (p < 0.05), which indicates depressive-like syndromes. However, the increased immobility time was significantly reduced by MJ (5-20 mg/kg) when compared with LPS-treated group. LPS administration also altered the levels of MDA, GSH, corticosterone and TNF alpha in mice, which was significantly reversed by MJ. These findings suggest that attenuation of LPS-induced depressive-like behavior by MJ may be related to suppression of oxidative stress and release of TNF alpha.

Alpha7 nicotinic acetylcholine receptor agonists and PAMs as adjunctive treatment in schizophrenia. An experimental study

Nicotine has been found to improve cognition and reduce negative symptoms in schizophrenia and a genetic and pathophysiological link between the α7 nicotinic acetylcholine receptors (nAChRs) and schizophrenia has been demonstrated. Therefore, there has been a large interest in developing drugs affecting the α7 nAChRs for schizophrenia. In the present study we investigated, in rats, the effects of a selective α7 agonist (PNU282987) and a α7 positive allosteric modulator (PAM; NS1738) alone and in combination with the atypical antipsychotic drug risperidone for their utility as adjunct treatment in schizophrenia. Moreover we also investigated their utility as adjunct treatment in depression in combination with the SSRI citalopram. We found that NS1738 and to some extent also PNU282987, potentiated a subeffective dose of risperidone in the conditioned avoidance response test. Both drugs also potentiated the effect of a sub-effective concentration of risperidone on NMDA-induced currents in pyramidal cells of the medial prefrontal cortex. Moreover, NS1738 and PNU282987 enhanced recognition memory in the novel object recognition test, when given separately. Both drugs also potentiated accumbal but not prefrontal risperidone-induced dopamine release. Finally, PNU282987 reduced immobility in the forced swim test, indicating an antidepressant-like effect. Taken together, our data support the utility of drugs targeting the α7 nAChRs, perhaps especially α7 PAMs, to potentiate the effect of atypical antipsychotic drugs. Moreover, our data suggest that α7 agonists and PAMs can be used to ameliorate cognitive symptoms in schizophrenia and depression.

Microinjection of cocaine- and amphetamine-regulated transcript 55-102 peptide into the nucleus accumbens could modulate anxiety-related behavior in rats

Cocaine- and amphetamine-regulated transcript (CART) peptide is abundantly expressed in the nucleus accumbens (NAcc) and is involved in stress, anxiety and reward responses. To examine the role of CART peptide in anxiety-related behavior, naïve rats were bilaterally injected with CART 55-102 peptide (0.5, 1.0 or 2.5 µg/0.5 µl/side) or vehicle into the NAcc. Following this, their anxiety-related behavior was assessed using the elevated plus maze and the open field tests with a one-week interval between the tests. There was no difference in the time spent in open arms, or number of entries into open arms on the elevated plus maze in the CART-treated animals at any dose, when compared with the vehicle-treated group. However, there was a significant increase in the time spent in the center of the open field with administration of the low dose of CART peptide (0.5 µg/0.5 µl/side), although this effect disappeared at the high dose (2.5 µg/0.5 µl/side). None of the doses of CART peptide altered total locomotion in these tests. To further determine the possible anxiety-modulating effect of CART peptide at low dosages, the light and dark test was performed. Additional groups of rats given doses of 0.01 µg/0.5 µl/side or 0.5 µg/0.5 µl/side of CART peptide showed increased exploration time in the light side. These results suggest that accumbal-CART peptide reduces anxiety-like behavior in a dose-dependent manner.

Animal models as tools to study the pathophysiology of depression

The incidence of depressive illness is high worldwide, and the inadequacy of currently available drug treatments contributes to the significant health burden associated with depression. A basic understanding of the underlying disease processes in depression is lacking; therefore, recreating the disease in animal models is not possible. Popular current models of depression creatively merge ethologically valid behavioral assays with the latest technological advances in molecular biology. Within this context, this study aims to evaluate animal models of depression and determine which has the best face, construct, and predictive validity. These models differ in the degree to which they produce features that resemble a depressive-like state, and models that include stress exposure are widely used. Paradigms that employ acute or sub-chronic stress exposure include learned helplessness, the forced swimming test, the tail suspension test, maternal deprivation, chronic mild stress, and sleep deprivation, to name but a few, all of which employ relatively short-term exposure to inescapable or uncontrollable stress and can reliably detect antidepressant drug response.

Effect of desipramine and citalopram treatment on forced swimming test-induced changes in cocaine- and amphetamine-regulated transcript (CART) immunoreactivity in mice

Recent study demonstrates antidepressant-like effect of cocaine- and amphetamine-regulated transcript (CART) in the forced swimming test (FST), but less is known about whether antidepressant treatments alter levels of CART immunoreactivity (CART-IR) in the FST. To explore this possibility, we assessed the treatment effects of desipramine and citalopram, which inhibit the reuptake of norepinephrine and serotonin into the presynaptic terminals, respectively, on changes in levels of CART-IR before and after the test swim in mouse brain. Levels of CART-IR in the nucleus accumbens shell (AcbSh), dorsal bed nucleus of the stria terminalis (dBNST), and hypothalamic paraventricular nucleus (PVN) were significantly increased before the test swim by desipramine and citalopram treatments. This increase in CART-IR in the AcbSh, dBNST, and PVN before the test swim remained elevated by desipramine treatment after the test swim, but this increase in these brain areas returned to near control levels after test swim by citalopram treatment. Citalopram, but not desipramine, treatment increased levels of CART-IR in the central nucleus of the amygdala (CeA) and the locus ceruleus (LC) before the test swim, and this increase was returned to control levels after the test swim in the CeA, but not in the LC. These results suggest common and distinct regulation of CART by desipramine and citalopram treatments in the FST and raise the possibility that CART in the AcbSh, dBNST, and CeA may be involved in antidepressant-like effect in the FST.

Changes in c-Fos Expression in the Forced Swimming Test: Common and Distinct Modulation in Rat Brain by Desipramine and Citalopram

Rodents exposed to a 15-min pretest swim in the forced swimming test (FST) exhibit prolonged immobility in a subsequent 5-min test swim, and antidepressant treatment before the test swim reduces immobility. At present, neuronal circuits recruited by antidepressant before the test swim remain unclear, and also less is known about whether antidepressants with different mechanisms of action could influence neural circuits differentially. To reveal the neural circuits associated with antidepressant effect in the FST, we injected desipramine or citalopram 0.5 h, 19 h, and 23 h after the pretest swim and observed changes in c-Fos expression in rats before the test swim, namely 24 h after the pretest swim. Desipramine treatment alone in the absence of pretest swim was without effect, whereas citalopram treatment alone significantly increased the number of c-Fos-like immunoreactive cells in the central nucleus of the amygdala and bed nucleus of the stria terminalis, where this pattern of increase appears to be maintained after the pretest swim. Both desipramine and citalopram treatment after the pretest swim significantly increased the number of c-Fos-like immunoreactive cells in the ventral lateral septum and ventrolateral periaqueductal gray before the test swim. These results suggest that citalopram may affect c-Fos expression in the central nucleus of the amygdala and bed nucleus of the stria terminalis distinctively and raise the possibility that upregulation of c-Fos in the ventral lateral septum and ventrolateral periaqueductal gray before the test swim may be one of the probable common mechanisms underlying antidepressant effect in the FST.

Amygdala nuclei critical for emotional learning exhibit unique gene expression patterns

The amygdala is a heterogeneous, medial temporal lobe structure that has been implicated in the formation, expression and extinction of emotional memories. This structure is composed of numerous nuclei that vary in cytoarchitectonics and neural connections. In particular the lateral nucleus of the amygdala (LA), central nucleus of the amygdala (CeA), and the basal (B) nucleus contribute an essential role to emotional learning. However, to date it is still unclear to what extent these nuclei differ at the molecular level. Therefore we have performed whole genome gene expression analysis on these nuclei to gain a better understanding of the molecular differences and similarities among these nuclei. Specifically the LA, CeA and B nuclei were laser microdissected from the rat brain, and total RNA was isolated from these nuclei and subjected to RNA amplification. Amplified RNA was analyzed by whole genome microarray analysis which revealed that 129 genes are differentially expressed among these nuclei. Notably gene expression patterns differed between the CeA nucleus and the LA and B nuclei. However gene expression differences were not considerably different between the LA and B nuclei. Secondary confirmation of numerous genes was performed by in situ hybridization to validate the microarray findings, which also revealed that for many genes, expression differences among these nuclei were consistent with the embryological origins of these nuclei. Knowing the stable gene expression differences among these nuclei will provide novel avenues of investigation into how these nuclei contribute to emotional arousal and emotional learning, and potentially offer new genetic targets to manipulate emotional learning and memory.

Region- and sex-specific changes in CART mRNA in rat hypothalamic nuclei induced by forced swim stress

Cocaine and amphetamine regulated transcript (CART) mRNA and peptides are highly expressed in the paraventricular (PVN), dorsomedial (DMH) and arcuate (ARC) nuclei of the hypothalamus. It has been suggested that these nuclei regulate the hypothalamic-pituitary-adrenal (HPA) axis, autonomic nervous system activity, and feeding behavior. Our previous studies showed that forced swim stress augmented CART peptide expression significantly in whole hypothalamus of male rats. In another study, forced swim stress increased the number of CART-immunoreactive cells in female PVN, whereas no effect was observed in male PVN or in the ARC nucleus of either sex. In the present study, we evaluated the effect of forced swim stress on CART mRNA expression in PVN, DMH and ARC nuclei in both male and female rats. Twelve male (stressed and controls, n=6 each) and 12 female (stressed and controls, n=6 each) Sprague-Dawley rats were used. Control animals were only handled, whereas forced swim stress procedure was applied to the stressed groups. Brains were dissected and brain sections containing PVN, DMH and ARC nuclei were prepared. CART mRNA levels were determined by in situ hybridization. In male rats, forced swim stress upregulated CART mRNA expression in DMH and downregulated it in the ARC. In female rats, forced swim stress increased CART mRNA expression in PVN and DMH, whereas a decrease was observed in the ARC nucleus. Our results show that forced swim stress elicits region- and sex-specific changes in CART mRNA expression in rat hypothalamus that may help in explaining some of the effects of stress.

The antidepressants citalopram and reboxetine reduce seizure frequency in rats with chronic epilepsy

PURPOSE

  For a long time, antidepressants have been thought to possess proconvulsant properties. This assumption, however, remains controversial, since anticonvulsant effects have been attributed to certain antidepressants. To date, it remains unclear which antidepressants can be used for the treatment of depression in patients with epilepsy. In this respect, studies investigating the convulsant liability of antidepressants in a chronic epilepsy model can give valuable information. The present study was designed to determine the seizure liability of citalopram and reboxetine in the kainic acid-induced post-status epilepticus model for temporal lobe epilepsy.

METHODS

  Two months after the induction of status epilepticus, chronic epileptic rats (n = 16) were video-electroencephalography (EEG) monitored during seven consecutive weeks. Weeks 1, 3, 5, and 7 served as sham weeks during which the rats received intraperitoneal saline injections for four consecutive days, followed by a 3-day sham washout period during which no injections were given. During weeks 2, 4, and 6, rats received intraperitoneal injections with either citalopram (5, 10, and 15 mg/kg, once daily, n = 8) or reboxetine (10, 20, and 30 mg/kg, twice daily, n = 8) for 4 days, again followed by a washout period of 3 days. Drugs were administered in a randomly assigned fixed-dose regimen per week. Each rat served as its own control. The drug doses were selected based on the doses reported to have antidepressant effects in rats.

KEY FINDINGS

  Citalopram significantly decreased the spontaneous seizure frequency at the highest dose tested, that is, the mean number of seizures decreased from 12.8 seizures to 8.8 seizures per week (31%) after treatment with 15 mg/kg citalopram. This dose also significantly decreased the cumulative seizure duration. Administration of 5 and 10 mg/kg citalopram did not alter the seizure frequency. The two highest doses of reboxetine significantly decreased the spontaneous seizure frequency, that is, 20 mg/kg reboxetine decreased the seizure frequency from 14.1 to 7.9 (44%) and 30 mg/kg reboxetine decreased the seizure frequency from 11.8 to 7.2 (39%). In addition, both doses significantly decreased the cumulative seizure duration. Administration of 10 mg/kg reboxetine did not alter seizure frequency. Citalopram and reboxetine had no effect on seizure severity and seizure duration in any of the doses tested.

SIGNIFICANCE

  In general we can conclude that antidepressant doses of citalopram and reboxetine have, depending on the dose, an anticonvulsant effect or no effect on spontaneous seizures in the kainic acid-induced post-status epilepticus rat model.

Behavioral interactions of simvastatin and fluoxetine in tests of anxiety and depression

Simvastatin inhibits 3-hydroxy-3-methylglutaryl CoA reductase, the rate-limiting enzyme in the cholesterol biosynthetic pathway, and is widely used to control plasma cholesterol levels and prevent cardiovascular disease. However, emerging evidence indicates that the beneficial effects of simvastatin extend to the central nervous system. The effects of simvastatin combined with fluoxetine provide an exciting and potential paradigm to decreased anxiety and depression. Thus, the present paper investigates the possibility of synergistic interactions between simvastatin and fluoxetine in models of anxiety and depression. We investigated the effects of subchronically administered simvastatin (1 or 10 mg/kg/day) combined with fluoxetine (2 or 10 mg/kg) at 24, 5, and 1 hour on adult rats before conducting behavioral tests. The results indicate that simvastatin and/or fluoxetine treatment reduces anxiety-like behaviors in the elevated plus-maze and open-field tests. Our results showed that simvastatin and/or fluoxetine induced a significant increase in the swimming activity during the forced swimming test (antidepressant effect), with a concomitant increase in climbing time in simvastatin-treated animals only (noradrenergic activation). We hypothesize that anxiolytic and antidepressant effects of simvastatin and/or fluoxetine produce their behavioral effects through similar mechanisms and provide an important foundation for future preclinical research.

CART peptide following social novelty in the prairie vole (Microtus ochrogaster)

Prairie voles (Microtus ochrogaster) are monogamous rodents that display high levels of affiliative behaviors, including pair-bonding, biparental care, and cooperative breeding. Species differences in basal cocaine- and amphetamine-regulated transcript (CART) mRNA and peptide expression have been found between prairie voles and polygamous meadow voles. Therefore, we hypothesized that the CART system may play a role in the regulation of social behavior in this species. Male and female adult prairie voles were placed in a cage either alone, or with a novel social partner of the same or opposite sex. After 45 min, subjects were sacrificed and CART peptide expression was examined using immunohistochemistry. We examined fifteen hypothalamic, limbic, and hindbrain regions of interest, focusing on areas that show species-specific patterns of expression. We found that subjects paired with a novel conspecific had lower levels of peptide in the bed nucleus of the stria terminalis (BNST) than isolated animals. This may reflect increased peptide release following increased dopaminergic activity in animals exposed to a novel conspecific. Additionally, CART peptide was higher in the nucleus accumbens (NAc) of subjects paired with an opposite sex partner compared to those paired with a same-sex conspecific, although there was no difference between isolated subjects and either socially housed group. These findings suggest that CART in the NAc is differentially responsive to the sex of adult conspecifics and that the social environment influences CART expression in the prairie vole in a region- and stimulus-specific manner.