Márcio R. Martins

The role of hippocampus in the pathophysiology of bipolar disorder.

Bipolar disorder (BD) is thought to be associated with abnormalities within discrete brain regions associated with emotional regulation, particularly in fronto-limbic-subcortical circuits. Several reviews have addressed the involvement of the prefrontal cortex in the pathophysiology of BD, whereas little attention has been given to the role of the hippocampus. This study critically reviews data from brain imaging, postmortem, neuropsychological, and preclinical studies, which suggested hippocampal abnormalities in BD. Most of the structural brain imaging studies did not find changes in hippocampal volume in BD, although a few studies suggested that anatomical changes might be restricted to the psychotic, pediatric, or unmedicated BD subgroups. Functional imaging studies showed abnormal brain activation in the hippocampus and its closely related regions during emotional, attentional, and memory tasks. This is consistent with neuropsychological findings that revealed a wide range of cognitive disturbances during acute mood episodes and a significant impairment in declarative memory during remission. Postmortem studies indicate abnormal glutamate and GABA transmission in the hippocampus of BD patients, whereas data from preclinical studies suggest that the regulation of hippocampal plasticity and survival might be associated with the therapeutic effects of mood stabilizers. In conclusion, the available evidence suggests that the hippocampus plays an important role in the pathophysiology of BD.

Cognitive impairment in sepsis survivors from cecal ligation and perforation

Objective:Critical illness survivors present long-term cognitive impairment, including problems with memory and learning. We evaluated cognitive performance in rats that survived from sepsis induced by cecal ligation and puncture (CLP). Design:Prospective, controlled experiment. Setting:Animal basic science laboratory. Subjects:Male Wistar rats, weighing 300–350 g. Interventions:The rats underwent CLP (sepsis group) with “basic support” (saline at 50 mL/kg immediately and 12 hrs after CLP plus ceftriaxone at 30 mg/kg and clindamycin at 25 mg/kg 6, 12, and 18 hrs after CLP) or sham-operated (control group). Measurements and Main Results:Ten days after surgery, the animals underwent three behavioral tasks: a) inhibitory avoidance task; b) habituation to an open field; and c) continuous multiple-trials step-down inhibitory avoidance task (CMSIA). In the habituation to an open-field task, there were no differences in the number of crossings and rearings. The sepsis group showed significantly decreased performance in latency retention compared with the sham group in inhibitory avoidance. Furthermore, when tested by the habituation to an open-field task, the sepsis group did not show any difference between training and test, indicating memory impairment. In the CMSIA, the sepsis group showed a significant increase in the number of training trials required to reach the acquisition criterion. Conclusion:Our data provide the first experimental demonstration that survivors from CLP show learning and memory impairment after complete physical recovery from sepsis.

Protective effect of N-acetylcysteine and deferoxamine on carbon tetrachloride-induced acute hepatic failure in rats.

Objective:Carbon tetrachloride (CCl4) is a lipid-soluble potent hepatotoxic; thus, it widely is used as an animal model of severe hepatic failure. Treatment with antioxidants may modulate the toxic effects of CCl4 on liver, generally with drug administration before CCl4, which can restrict its use in the clinical setting. We here describe the effects of N-acetylcysteine, deferoxamine, or both in the treatment of CCl4-induced hepatic failure. Design:Prospective, randomized, controlled experiment. Setting:Animal basic science laboratory. Subjects:Male Wistar rats, weighing 200–250 g. Interventions:Rats exposed to CCl4 were treated with N-acetylcysteine and/or deferoxamine or vehicle. Measurements and Main Results:N-acetylcysteine plus deferoxamine treatment significantly attenuated hepatic and central nervous system oxidative damage after acute hepatic failure induced by CCl4. In addition, the serum levels of alanine aminotransferase, total bilirubin, and prothrombin time in the N-acetylcysteine plus deferoxamine group were significantly lower than those in the N-acetylcysteine or deferoxamine and saline groups. After N-acetylcysteine plus deferoxamine treatment, hepatocellular necrosis and inflammatory infiltration induced by carbon tetrachloride were greatly decreased. Survival in untreated rats was 5%. Survival increased to 25% and 35%, respectively, with N-acetylcysteine and deferoxamine treatment. In rats treated with N-acetylcysteine plus deferoxamine, survival was 80%. Conclusions:Our data provide the first experimental demonstration that N-acetylcysteine plus deferoxamine reduces mortality rate, decreases oxidative stress, and limits inflammatory infiltration and hepatocyte necrosis induced by CCl4 in the rat.

Haloperidol and clozapine, but not olanzapine, induces oxidative stress in rat brain

Typical and atypical antipsychotic drugs have been shown to have different clinical and behavioral profiles. Haloperidol (HAL) is a typical neuroleptic that acts primarily as a D2 dopamine receptor antagonist. It has been proposed that reactive oxygen species play a causative role in neurotoxic effects induced by HAL. We evaluated oxidative damage in rat brain induced by chronic HAL, clozapine (CLO) or olanzapine (OLZ) administration. Adult male Wistar rats received daily injections of Hal (1.5mg/kg), CLO (25mg/kg) or OLZ (2.5, 5.0 or 10.0mg/kg). Control animals were given saline (SAL; NaCl 0.9%). Thiobarbituric acid reactive substances (TBARS) and protein carbonylation were measured in the hippocampus (HP), striatum (ST) and cortex (CX). TBARS was increased in the striatum after HAL treatment. In contrast, there was a decrease of TBARS levels induced by HAL, CLO and OLZ treatments in the cortex. Protein carbonyls after HAL and CLO treatment was increased in the hippocampus, compared to control. In hippocampus, OLZ did not show significant difference to control in both oxidative parameters. Our findings demonstrated that atypical antipsychotic CLO produced less oxidative damage than HAL and we did not find oxidative damage induced by OLZ.

Increased oxidative stress in submitochondrial particles after chronic amphetamine exposure

Previous studies have suggested that reactive oxygen species (ROS) production may play a role in the pathophysiology of many neuropsychiatric disorders, such as bipolar disorder (BD) and schizophrenia (SCZ). In addition, there is an emerging body of data indicating that BD and SCZ may be associated with mitochondrial dysfunction. We studied the effects of acute and chronic d-amphetamine on ROS production in submitochondrial particles of rat brain. Male Wistar rats were divided in two experimental groups: acute and chronic treatment. In the acute treatment, rats received one single IP injection of d-amphetamine (1, 2 or 4 mg/kg) or saline (control group). In the chronic treatment, rats received one daily IP injection of d-amphetamine (1, 2 or 4 mg/kg) or saline for 7 days. Locomotor activity was assessed with the open field task, and thiobarbituric acid reactive substances (TBARS) and superoxide production were measured in submitochondrial particles of the prefrontal cortex and hippocampus. Both acute and chronic amphetamine treatment increased locomotor behavior. Chronic amphetamine exposure induced a 3- to 6-fold increase of TBARS and a 1.5- to 2-fold increase of superoxide production in submitochondrial particles of prefrontal cortex and hippocampus (P < 0.05). No effects on superoxide or TBARS were observed with acute treatment. These findings suggest that amphetamine-induced mitochondrial ROS generation may be a useful model to investigate the hypothesis of altered brain energy metabolism associated with BD and SCZ. Further studies assessing the effects of mood stabilizers and antipsychotics in preventing mitochondrial oxidative stress are necessary.

Methylphenidate treatment induces oxidative stress in young rat brain

Methylphenidate (MPH) is frequently prescribed for the treatment of attention deficit/hyperactivity disorder. Psychostimulants can cause long-lasting neurochemical and behavioral adaptations. Here, we evaluated oxidative damage in the rat brain and the differential age-dependent response to MPH after acute and chronic exposure. We investigated the oxidative damage, assessed by the thiobarbituric acid reactive species (TBARS), and the protein carbonyl assays in cerebellum, prefrontal cortex, hippocampus, striatum, and cerebral cortex of young (25 days old) and adult (60 days old) male Wistar rats after acute and chronic exposure to MPH. Chronic MPH-treated young rats presented a dose-dependent increase in TBARS content and protein carbonyls formation in specific rat brain regions. In the acute exposure, only MPH highest dose increased lipid peroxidation in the hippocampus. No difference in protein carbonylation was observed among groups in all structures analyzed. In adult rats, we did not find oxidative damage in both acute and chronic treatment. Chronic exposure to MPH in induces oxidative damage in young rat brain, differentially from chronic exposure during adulthood. These findings highlight the need for further research to improve understanding of MPH effects on developing nervous system and the potential consequences in adulthood resulting from early-life drug exposure.

Antioxidant treatment prevented late memory impairment in an animal model of sepsis.

Objective:Assess the effect of antioxidant treatment on late memory impairment and early hippocampus oxidative stress after cecal ligation and perforation. Subjects:Male Wistar rats. Interventions:Rats underwent sham operation or cecal ligation and perforation. Animals that underwent cecal ligation and perforation were divided into groups: 1) treated with basic support (50 mL/kg saline, 30 mg/kg ceftriaxone, and 25 mg/kg clindamycin every 6 hrs), 2) treated with basic support plus N-acetylcysteine (20 mg/kg N-acetylcysteine at 3, 6, 12, 18, and 24 hrs after cecal ligation and perforation), 3) treated with basic support plus deferoxamine (20 mg/kg deferoxamine at 3 and 24 hrs after cecal ligation and perforation), 4) treated with basic support plus N-acetylcysteine and deferoxamine, or 5) treated with N-acetylcysteine plus deferoxamine. Measurements and Main Results:On days 10 and 30 after surgery, the animals underwent behavioral tasks: inhibitory avoidance task, habituation to an open field, and continuous multiple-trials step-down inhibitory avoidance task. The sepsis group showed significantly decreased performance in latency retention compared with the sham group in the inhibitory avoidance task. In the open-field task, the sepsis group presented memory impairment after sepsis. In the continuous multiple-trials step-down inhibitory avoidance task, the sepsis group showed a significant increase in the number of training trials required to reach the acquisition criterion. All these memory impairments were prevented by N-acetylcysteine plus deferoxamine treatment, but not its isolate use. In addition, the combined use of antioxidants attenuated oxidative damage in hippocampus 6 hrs after sepsis induction. Conclusions:Antioxidant treatment prevented the development of late cognitive deficits in an animal model of sepsis.

Protein synthesis, PKA, and MAP kinase are differentially involved in short- and long-term memory in rats

We studied the involvement of hippocampal protein synthesis-, PKA-, and MAP kinase-dependent processes in short- (STM) and long-term memory (LTM) for inhibitory avoidance task. Fifteen minutes before or immediately after training rats received intrahippocampal infusions of vehicle, the protein synthesis inhibitor anisomycin, the PKA inhibitor Rp-cAMPs or the MAPKK inhibitor PD098059. The results show that STM recruits PKA and MAPK, whereas, LTM depends on PKA activity and protein synthesis during the early post-training period.

The Aqueous Extracts of Passiflora alata and Passiflora edulis Reduce Anxiety-Related Behaviors Without Affecting Memory Process in Rats

Several species of Passiflora have been employed widely as a folk medicine because of sedative and tranquillizer activities. In this study, we evaluate the effects on anxiety and memory process of two popularly used Passiflora species. To this aim, male Wistar rats (weighing 250-300 g) were intraperitoneally injected with the aqueous extract of Passiflora alata or Passiflora edulis (25, 50, 100, or 150 mg/kg; single injection) 30 minutes prior to the elevated plus-maze test, inhibitory avoidance test, or habituation to an open-field apparatus. The effects of both species of Passiflora were compared with that of diazepam (1 mg/kg), a standard anxiolytic drug. Our findings revealed that, similar to diazepam, the treatment with P. alata (100 and 150 mg/kg) and P. edulis (50, 100, and 150 mg/kg) induced anxiolytic-like effects in rats. Memory was not affected by the treatment with any dose of P. alata or P. edulis, but diazepam disrupted memory process in rats. Phytochemical analysis showed that the content of flavonoids of the aqueous extract of P. edulis is almost twice that of P. alata. These differences in contents of flavonoids could explain the lower active doses of the aqueous extract of P. edulis in inducing anxiolytic-like effects compared to P. alata. In conclusion, our findings suggest that, distinct from diazepam, the aqueous extract of both species of Passiflora induced anxiolytic-like effects in rats without disrupting memory process.

Antipsychotic-induced oxidative stress in rat brain.

Typical and atypical antipsychotic drugs have been shown to have different clinical and behavioral profiles. Haloperidol (HAL) is a typical neuroleptic that acts primarily as a D2 dopamine receptor antagonist. It has been proposed that reactive oxygen species play a causative role in neurotoxic effects induced by HAL. We evaluated oxidative damage in rat brain induced by chronic (28 days) HAL, clozapine (CLO), olanzapine (OLZ) or aripiprazole (ARI) administration. Adult male Wistar rats received daily injections of HAL (1.5 mg/kg), CLO (25 mg/kg), OLZ (2.5, 5 or 10 mg/kg) or ARI (2, 10 or 20 mg/kg); control animals received vehicle (Tween 1% solution). Thiobarbituric acid reactive substances (TBARS) and protein carbonylation were measured in the prefrontal cortex, hippocampus, striatum and cerebral cortex. The results showed that TBARS were increased in the striatum after HAL treatment. On the other hand, TBARS were diminished in the prefrontal cortex by OLZ and ARI. Our results also showed that all drugs tested in this work decreased TBARS levels in the cerebral cortex. In hippocampus, TBARS levels were not altered by any drug. Protein carbonyl content after HAL and CLO treatment was increased in the hippocampus. Moreover, OLZ and ARI did not alter protein carbonyl content when compared to control group. ARI chronic administration (20 mg/kg) also increased mitochondrial superoxide in the prefrontal cortex and striatum. ARI did not alter mitochondrial superoxide in the hippocampus and cerebral cortex. Moreover, HAL, OLZ and CLO did not cause significant alterations in mitochondrial superoxide in rat brain. Our findings demonstrate that OLZ and ARI do not induce oxidative damage in rat brain as observed after HAL and CLO treatment.