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Studies have shown a relationship between diabetes mellitus (DM) and the development of major depressive disorder. Alterations in oxidative stress are associated with the pathophysiology of both diabetes mellitus and major depressive disorder. This study aimed to evaluate the effects of antioxidants N-acetylcysteine and deferoxamine on behaviour and oxidative stress parameters in diabetic rats. To this aim, after induction of diabetes by a single dose of alloxan, Wistar rats were treated with N-acetylcysteine or deferoxamine for 14 days, and then depressive-like behaviour was evaluated. Oxidative stress parameters were assessed in the prefrontal cortex, hippocampus, amygdala, nucleus accumbens and pancreas. Diabetic rats displayed depressive-like behaviour, and treatment with N-acetylcysteine reversed this alteration. Carbonyl protein levels were increased in the prefrontal cortex, hippocampus and pancreas of diabetic rats, and both N-acetylcysteine and deferoxamine reversed these alterations. Lipid damage was increased in the prefrontal cortex, hippocampus, amygdala and pancreas; however, treatment with N-acetylcysteine or deferoxamine reversed lipid damage only in the hippocampus and pancreas. Superoxide dismutase activity was decreased in the amygdala, nucleus accumbens and pancreas of diabetic rats. In diabetic rats, there was a decrease in catalase enzyme activity in the prefrontal cortex, amygdala, nucleus accumbens and pancreas, but an increase in the hippocampus. Treatment with antioxidants did not have an effect on the activity of antioxidant enzymes. In conclusion, animal model of diabetes produced depressive-like behaviour and oxidative stress in the brain and periphery. Treatment with antioxidants could be a viable alternative to treat behavioural and biochemical alterations induced by diabetes.

A growing body of evidence points toward an association between the glutamatergic system, as well as immune system dysregulation and major depression. So, the present study was aimed at evaluating the behavioral and molecular effects of the ketamine, an antagonist of the N-methyl-D-aspartate (NMDA) receptor of glutamate in maternally deprived adult rats. In deprived rats treated with saline, we observed an increase in the immobility time; however, ketamine treatment reversed this effect, decreasing immobility time. In addition, maternal deprivation induced an increase in cytokines: TNF-α and IL-1 in serum, and in IL-6 in serum and cerebrospinal fluid (CSF). Interestingly, ketamine treatment reduced the levels of all the cytokines in deprived rats. In conclusion, these findings further support a relationship between immune activation and depression. Considering the action of ketamine, this study suggested that antagonists of the NMDA receptor, such as ketamine, could exert their effects by modulation of the immune system.

Studies have pointed to a relationship between MAPK kinase (MEK) signaling and the behavioral effects of antidepressant drugs. So, in the present study we examined the behavioral and molecular effects of ketamine, an antagonist of the N-methyl-d-aspartate receptor (NMDA), which has been shown to have an antidepressant effect after the inhibition of MEK signaling in Wistar rats. Our results showed that acute administration of the MEK inhibitor PD184161, produced depressive-like behavior and stopped antidepressant-like effects of ketamine in the forced swimming test. The phosphorylation of extracellular signal-regulated kinase 1/2 (pERK 1/2) was decreased by PD184161 in the amygdala and nucleus accumbens, and the effects of ketamine on pERK 1/2 in the prefrontal cortex and hippocampus were inhibited by PD184161. The ERK 2 levels were decreased by PD184161 in the nucleus accumbens; and the effects of ketamine were blocked in this brain area. The p38 protein kinase (p38MAPK) and proBDNF were inhibited by PD184161, and the MEK inhibitor prevented the effects of ketamine in the nucleus accumbens. In addition, ketamine increased pro-BDNF levels in the hippocampus. In conclusion, our findings demonstrated that an acute blockade of MAPK signaling lead to depressive-like behavior and stopped the antidepressant response of ketamine, suggesting that the effects of ketamine could be mediated, at least in part, by the regulation of MAPK signaling in these specific brain areas.

Maternally deprived rats were treated with tianeptine (15 mg/kg) once a day for 14 days during their adult phase. Their behavior was then assessed using the forced swimming and open field tests. The BDNF, NGF and energy metabolism were assessed in the rat brain. Deprived rats increased the immobility time, but tianeptine reversed this effect and increased the swimming time; the BDNF levels were decreased in the amygdala of the deprived rats treated with saline and the BDNF levels were decreased in the nucleus accumbens within all groups; the NGF was found to have decreased in the hippocampus, amygdala and nucleus accumbens of the deprived rats; citrate synthase was increased in the hippocampus of non-deprived rats treated with tianeptine and the creatine kinase was decreased in the hippocampus and amygdala of the deprived rats; the mitochondrial complex I and II-III were inhibited, and tianeptine increased the mitochondrial complex II and IV in the hippocampus of the non-deprived rats; the succinate dehydrogenase was increased in the hippocampus of non-deprived rats treated with tianeptine. So, tianeptine showed antidepressant effects conducted on maternally deprived rats, and this can be attributed to its action on the neurochemical pathways related to depression.

Recent studies show that activation of the mTOR signaling pathway is required for the rapid antide- pressant actions of glutamate N-methyl-D-aspartate (NMDA) receptor antagonists. A relationship be- tween mTOR kinase and the endoplasmic reticulum (ER) stress pathway, also known as the unfolded protein response (UPR) has been shown. We evaluate the effects of ketamine administration on the mTOR signaling pathway and proteins of UPR in the prefrontal cortex (PFC), hippocampus, amygdala and nucleus accumbens, after the inhibiton of mTOR signaling in the PFC. Male adult Wistar rats received pharmacological mTOR inhibitor, rapamycin (0.2 nmol), or vehicle into the PFC and then a single dose of ketamine (15 mg/kg, i.p.). The immunocontent of mTOR, eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), eukaryotic elongation factor 2 kinase (eEF2K) homologous protein (CHOP), PKR-like ER kinase (PERK) and inositol-requiring enzyme 1 (IRE1) e alpha were determined in the brain. The mTOR levels were reduced in the rapamycin group treated with saline and ketamine in the PFC; p4EBP1 levels were reduced in the rapamycin group treated with ketamine in the PFC and nucleus accumbens; the levels of peEF2K were increased in the PFC in the vehicle group treated with ketamine and reduced in the rapamycin group treated with ketamine. The PERK and IRE1-alpha levels were decreased in the PFC in the rapamycin group treated with ketamine. Our results suggest that mTOR signaling inhibition by rapamycin could be involved, at least in part, with the mechanism of action of ketamine; and the ke- tamine antidepressant on ER stress pathway could be also mediated by mTOR signaling pathway in certain brain structures.

Studies indicated that mammalian target of rapamycin (mTOR), oxidative stress, and inflammation are involved in the pathophysiology of major depressive disorder (MDD). Ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, has been identified as a novel MDD therapy; however, the antidepressant mechanism is not fully understood. In addition, the effects of ketamine after mTOR inhibition have not been fully investigated. In the present study, we examined the behavioral and biochemical effects of ketamine in the prefrontal cortex (PFC), hippocampus, amygdala, and nucleus accumbens after inhibition of mTOR signaling in the PFC. Male adult Wistar rats received pharmacological mTOR inhibitor, rapamycin (0.2 nmol) or vehicle into the PFC and then a single dose of ketamine (15 mg/kg, i.p.). Immobility was assessed in forced swimming tests, and then oxidative stress parameters and inflammatory markers were evaluated in the brain and periphery. mTOR activation in the PFC was essential to ketamine’s antidepressant-like effects. Ketamine increased lipid damage in the PFC, hippocampus, and amygdala. Protein carbonyl was elevated in the PFC, amygdala, and NAc after ketamine administration. Ketamine also increased nitrite/nitrate in the PFC, hippocampus, amygdala, and NAc. Myeloperoxidase activity increased in the hippocampus and NAc after ketamine administration. The activities of superoxide dismutase and catalase were reduced after ketamine administration in all brain areas studied. Inhibition of mTOR signaling pathways by rapamycin in the PFC was required to protect against oxidative stress by reducing damage and increasing antioxidant enzymes. Finally, the TNF-α level was increased in serum by ketamine; however, the rapamycin plus treatment group was not able to block this increase. Activation of mTOR in the PFC is involved in the antidepressant-like effects of ketamine; however, the inhibition of this pathway was able to protect certain brain areas against oxidative stress, without affecting inflammation parameters.

Animal models of chronic stress represent valuable tools by which to investigate the behavioral, endocrine and neurobiological changes underlying stress-related psychopathologies, such as major depression, and the efficacy of antidepressant therapies. The present study was aimed at investigating the neurochemical effects of the antidepressant tianeptine in rats exposed to the chronic stress model. To this aim, rats were subjected to 40days of chronic unpredictable stressful stimuli, after which the animals received saline or tianeptine (15mg/kg) once a day for 7days. Additionally, IL-6, IL-1, TNF-α levels and oxidative stress parameters were assessed in the prefrontal cortex (PFC), hippocampus (HPC), amygdala (AMY) and nucleus accumbens (NAc) in all of the experimental groups studied. The results indicated that chronic mild stress and tianeptine did not exercise any effects on cytokines in all of the structures studied; in the PFC and AMY thiobarbituric acid reactive substances (TBARS) levels were decreased in control rats treated with tianeptine in the HPC; superoxide dismutase (SOD) activity was found to have decreased in stressed rats treated with saline in the PFC, HPC, AMY and NAc, and tianeptine reversed this effect; catalase (CAT) activity was found to have decreased in the PFC, HPC and NAc of stressed rats treated with saline, but was shown to have increased in stressed rats treated with tianeptine, and tianeptine also reversed the decreases in CAT activity in stressed rats treated with saline, suggesting that tianeptine exerted antioxidant activity. In conclusion, the present findings open new vistas on the pharmacological activity of tianeptine, in particular, concerning its ability to attenuate oxidative stress.

This study was designed to investigate the effects of treatment with the antioxidants N-acetylcysteine (NAC) and deferoxamine (DFX) in intracellular pathways in the brain of diabetic rats. To conduct this study we induced diabetes in Wistar rats with a single injection of alloxan, and afterwards rats were treated with NAC or DFX for 14 days. Following treatment completion, the immunocontent of c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase-38 (MAPK38), brain-derived neurotrophic factor (BDNF), and protein kinases A and C (PKA and PKC) were determined in the prefrontal cortex (PFC), hippocampus, amygdala and nucleus accumbens (NAc). DFX treatment increased JNK content in the PFC and NAc of diabetic rats. In the amygdala, JNK was increased in diabetics treated with saline or NAC. MAPK38 was decreased in the PFC of control and in diabetic rats treated with NAC or DFX; and in the NAc in all groups. PKA was decreased in the PFC with DFX treatment. In the amygdala, PKA content was increased in diabetic rats treated with either saline or NAC, compared to controls; and it was decreased in either NAC or DFX-treated groups, compared to saline-treated diabetic animals. In the NAc, PKA was increased in NAC-treated diabetic rats. PKC was increased in the amygdala of NAC-treated diabetic rats. In the PFC, the BDNF levels were decreased following treatment with DFX in diabetic rats. In the hippocampus of diabetic rats the BDNF levels were decreased. However, treatment with DFX reversed this effect. In the amygdala the BDNF increased with DFX in non-diabetic rats. In the NAc DFX treatment increased the BDNF levels in diabetic rats. In conclusion, both diabetes and treatment with antioxidants were able to alter intracellular pathways involved in the regulation of cell survival in a brain area and treatment-dependent fashion.

Background Ketamine, an antagonist of N-methyl- d -aspartate (NMDA) receptors, has presented antidepressant effects in basic and clinical studies. The MAPK kinase (MEK) signaling pathway could be a target for novel antidepressant drugs and an important pathway involved in neuronal plasticity. Thus, this study evaluated the effects of the administration of ketamine on the phosphorylation of TrKB and CREB, and oxidative stress parameters in the prefrontal cortex (PFC), hippocampus, amygdala, and nucleus accumbens (NAc) rats, after the inhibition of MAPK pathway (PD184161). Methods Male adult Wistar rats were submitted to a surgical procedure to receive a single dose of a pharmacological inhibitor of MAPK (PD184161) at a dose of (0.1 μg/μl) or vehicle. Then, they were divided: 1) vehicle + saline; 2) inhibitor PD184161 + saline; 3) vehicle + ketamine 15 mg/kg; and 4) inhibitor PD184161 + ketamine 15 mg/kg. Results MEK inhibitor and ketamine increased the phosphorylation of the transcription factor cAMP response element-binding protein (pCREB) and neurotrophic factor/tropomyosin related kinase B receptor (pTrKB) in the PFC, and decreased pCREB in the hippocampus. The MEK inhibitor abolished ketamine's effects in the hippocampus. In the amygdala, pCREB was decreased, and pTrKB was increased after MEK inhibitor plus ketamine. Ketamine increased the thiobarbituric acid reactive species (TBARS) in the PFC, hippocampus, amygdala, and NAc; MEK inhibitor antagonized these effects. The carbonyl was increased in the PFC by both ketamine and MEK inhibitor, but inhibitor infusion plus ketamine administration reduced this effect. In the amygdala, MEK inhibitor increased carbonyl. Conclusion Ketamine's effects on pCREB, pTrKB, and oxidative stress are mediated, at least in part, by a mechanism dependent of MAPK signaling inhibition.

Studies have suggested that ketamine, a nonselective NMDA receptor antagonist, could be a new drug in the treatment of major depression, but the way ketamine presents such effects remains to be elucidated. Therefore, the objective of this paper was to evaluate the effects of ketamine treatment on parameters related to depression in the brain of adult rats subjected to an animal model of depression. The animals were divided into: non-deprived + saline; non-deprived + ketamine; deprived + saline; deprived + ketamine. Treatments involving ketamine (15 mg/kg) were administered once a day during 14 days in the animal’s adult phase. After treatment, the brain derived-neurotrophic factor (BDNF) levels, oxidative stress and energy metabolism activity were evaluated in brain structures of rats involved in the circuit of depression. In the amygdala, hippocampus and nucleus accumbens (NAc), a reduction in BDNF levels was observed in deprived rats, but the animals treated with ketamine reversed the effects of this animal model only in the amygdala and NAc. In addition to this, the complex I activity, in deprived rats, was diminished in the prefrontal cortex (PFC) and amygdala; in the PFC and hippocampus, the complex II-III was diminished in deprived rats; still the administration of ketamine increased the complex IV activity in the PFC and amygdala of rats submitted to the maternal deprivation. In deprived rats, the creatine kinase activity was reduced in the PFC and amygdala, however the administration of ketamine reversed this decrease in the amygdala. The malondialdehyde (MDA) equivalents were increased in non-deprived rats treated with ketamine in the PFC and NAc. Carbonyl levels in the PFC were diminished in control rats that received saline. Though ketamine treatment reversed this effect in deprived rats in the PFC and hippocampus. Still, in NAc, the carbonyl levels were diminished in deprived rats. The superoxide dismutase (SOD) activity was increased in control rats that received ketamine in the PFC and NAc, and were diminished in deprived rats that received saline or ketamine in the PFC and hippocampus. These findings may help to explain that dysfunctions involving BDNF, oxidative stress and energy metabolism within specific brain areas, may be linked with the pathophysiology of depression, and antidepressant effects of ketamine can be positive, at least partially due to the control of these pathways.

Studies indicate that histone deacetylation is important for long term changes related to stress and antidepressant treatment. The present study aimed to evaluate the effects of the classic antidepressant imipramine, and of an antagonist of the N-methyl-d-asparte (NMDA) receptor, ketamine, on behavior and histone deacetylase (HDAC) activity in the brains of maternally deprived adult rats. To this aim, deprived and non-deprived (control) male Wistar rats were divided into the following groups: non-deprived+saline; non-deprived+imipramine (30 mg/kg); non-deprived+ketamine (15 mg/kg); deprived+saline; deprived+imipramine (30 mg/kg); and deprived+ketamine (15 mg/kg). The drugs were administrated once a day for 14 days during their adult phase. Their behavior were then assessed using the forced swimming and open field tests. In addition, the HDAC activity was evaluated in the prefrontal cortex, hippocampus, amygdala and nucleus accumbens using the kit ELISA-sandwich test. In deprived rats treated with saline, we observed an increase in the immobility time, but treatments with imipramine and ketamine were able to reverse this alteration, decreasing the immobility time. Also, there was a decrease on number of crossings with imipramine treatment in non-deprived rats, and an increase on number of crossings with ketamine treatment in deprived rats. The HDAC activity did not alter in the prefrontal cortex, hippocampus and amygdala by deprivation or via treatment with imipramine or ketamine. However, in the nucleus accumbens we observed an increase of HDAC activity in the deprived rats, and interestingly, imipramine and ketamine treatments were able to decrease HDAC activity in this brain area. These findings provide a novel insight into the epigenetic regulation of histone deacetylase in the nucleus accumbens caused by imipramine and ketamine, and indicate that molecular events are necessary to reverse specific stress-induced behavior.

A growing body of evidence is pointing toward an association between immune molecules, as well brain-derived neurotrophic factor (BDNF) and the depression. The present study was aimed to evaluate the behavioral and molecular effects of the antidepressant imipramine in maternally deprived adult rats. To this aim, maternally deprived and non-deprived (control group) male rats were treated with imipramine (30mg/kg) once a day for 14 days during their adult phase. Their behavior was then assessed using the forced swimming test. In addition to this, IL-10, TNF-α and IL-1β cytokines were assessed in the serum and cerebrospinal fluid (CSF). In addition, BDNF protein levels were assessed in the prefrontal cortex, hippocampus and amygdala. In deprived rats treated with saline was observed an increase on immobility time, compared with non-deprived rats treated with imipramine (p