The Role of HPA Axis and Allopregnanolone on the Neurobiology of Major Depressive Disorders and PTSD.

Under stressful conditions, the hypothalamic-pituitary-adrenal (HPA) axis acts to promote transitory physiological adaptations that are often resolved after the stressful stimulus is no longer present. In addition to corticosteroids (e.g., cortisol), the neurosteroid allopregnanolone (3α,5α-tetrahydroprogesterone, 3α-hydroxy-5α-pregnan-20-one) participates in negative feedback mechanisms that restore homeostasis. Chronic, repeated exposure to stress impairs the responsivity of the HPA axis and dampens allopregnanolone levels, participating in the etiopathology of psychiatric disorders, such as major depressive disorder (MDD) and post-traumatic stress disorder (PTSD). MDD and PTSD patients present abnormalities in the HPA axis regulation, such as altered cortisol levels or failure to suppress cortisol release in the dexamethasone suppression test. Herein, we review the neurophysiological role of allopregnanolone both as a potent and positive GABAergic neuromodulator but also in its capacity of inhibiting the HPA axis. The allopregnanolone function in the mechanisms that recapitulate stress-induced pathophysiology, including MDD and PTSD, and its potential as both a treatment target and as a biomarker for these disorders is discussed.

Neurosteroids and Neurotrophic Factors: What Is Their Promise as Biomarkers for Major Depression and PTSD?

Even though major depressive disorder (MDD) and post-traumatic stress disorder (PTSD) are among the most prevalent and incapacitating mental illnesses in the world, their diagnosis still relies solely on the characterization of subjective symptoms (many of which are shared by multiple disorders) self-reported by patients. Thus, the need for objective measures that aid in the detection of and differentiation between psychiatric disorders becomes urgent. In this paper, we explore the potential of neurosteroids and neurotrophic proteins as biomarkers for MDD and PTSD. Circulating levels of the GABAergic neuroactive steroid, allopregnanolone, are diminished in MDD and PTSD patients, which corroborates the finding of depleted neurosteroid levels observed in animal models of these disorders. The neurotrophic protein, brain-derived neurotropic factor (BDNF), is also reduced in the periphery and in the brain of MDD patients and depressed-like animals that express lower neurosteroid levels. Although the role of BDNF in PTSD psychopathology seems less clear and merits more research, we propose a causal link between allopregnanolone levels and BDNF expression that could function as a biomarker axis for the diagnosis of both MDD and PTSD.

Correction to: Symptoms Suggestive of Dysphagia and the Quality of Life in Cocaine and/or Crack Users.

The original version of this article unfortunately contained a mistake. The spelling of the Sheila Taminini de Almeida name was incorrect.

Six-Month Outcomes of a Randomized, Motivational Tele-intervention for Change in the Codependent Behavior of Family Members of Drug Users.

Families of substance abusers may develop maladaptive strategies, such as codependency, to address drug-related problems. It is important for families to receive specialist treatment in order to contribute to the recovery process. The Tele-intervention Model and Monitoring of Families of Drug Users (TMMFDU), based on motivational interviewing and stages of change, aims to encourage the family to change the codependents' behaviors. A randomized clinical trial was carried out to verify the change in codependent behavior after intervention with 6 months of follow-up. Three hundred and twenty-five families with high or low codependency scores were randomized into the intervention group (n = 163) or the usual treatment (UT) (n = 162). After 6 months of follow-up, the family members of the TMMFDU group were twice as likely to modify their codependency behavior when compared to the UT group (OR 2.08 CI 95% 1.18-3.65). TMMFDU proved to be effective in changing codependent behaviors among compliant family members of drug users.

Diabetic encephalopathy-related depression: experimental evidence that insulin and clonazepam restore antioxidant status in rat brain.

There is increasing evidence suggesting that oxidative stress plays an important role in the development of many chronic and degenerative conditions such as diabetic encephalopathy and depression. Considering that diabetic rats and mice present higher depressive-like behaviour when submitted to the forced swimming test and that treatment with insulin and/or clonazepam is able to reverse the behavioural changes of the diabetic rats, the present work investigated the antioxidant status, specifically total antioxidant reactivity and antioxidant potential of insulin and clonazepam, as well as the effect of this drugs upon protein oxidative damage and reactive species formation in cortex, hippocampus and striatum from diabetic rats submitted to forced swimming test. It was verified that longer immobility time in diabetic rats and insulin plus clonazepam treatment reversed this depressive-like behaviour. Moreover, data obtained in this study allowed to demonstrate through different parameters such as protein carbonyl content, 2'7'-dichlorofluorescein oxidation, catalase, superoxide dismutase, glutathione peroxidase assay, total radical-trapping antioxidant potential and total antioxidant reactivity that there is oxidative stress in cortex, hippocampus and striatum from diabetic rats under depressive-like behaviour and highlight the insulin and/or clonazepam effect in these different brain areas, restoring antioxidant status and protein damage.

Brain effect of insulin and clonazepam in diabetic rats under depressive-like behavior.

Diabetes mellitus is characterized by hyperglycemia resulting from defects on insulin secretion, insulin action, or both. It has recently become clear that the central nervous system is not spared from the deleterious effects of diabetes, since diabetic encephalopathy was recognized as a complication of this heterogeneous metabolic disorder. There is a well recognized association between depression and diabetes, once prevalence of depression in diabetic patients is higher than in general population, and clonazepam is being used to treat this complication. Oxidative stress is widely accepted as playing a key mediatory role in the development and progression of diabetes and its complications. In this work we analyzed DNA damage by comet assay and lipid damage in prefrontal cortex, hippocampus and striatum of streptozotocin-induced diabetic rats submitted to the forced swimming test. It was verified that the diabetic group presented DNA and lipid damage in the brain areas evaluated, when compared to the control groups. Additionally, a significant reduction of the DNA and lipid damage in animals treated with insulin and/or clonazepam was observed. These data suggest that the association of these two drugs could protect against DNA and lipid damage in diabetic rats submitted to the forced swimming test, an animal model of depression.

The association effect of insulin and clonazepam on oxidative stress in liver of an experimental animal model of diabetes and depression.

CONTEXT: It is known that oxidative stress occurs in peripheral blood in an experimental animal model of diabetes and depression, and acute treatment with insulin and clonazepam (CNZ) has a protective effect on oxidative stress in this model. OBJECTIVE: This study evaluated the effect of insulin plus CNZ on oxidative stress parameters in the liver of diabetic male rats induced with streptozotocin (STZ) and subjected to forced swimming test (FST). MATERIALS AND METHODS: Diabetes was induced by a single intraperitoneal (i.p.) dose of STZ 60 mg/kg in male Wistar rats. Insulin (4 IU/kg) plus CNZ acute i.p. treatment (0.25 mg/kg) was administered 24, 5 and 1 h before the FST. Nondiabetic control rats received i.p. injections of saline (1 mL/kg). Protein oxidative damage was evaluated by carbonyl formation and the antioxidant redox parameters were analyzed by the measurements of enzymatic activities of the superoxide dismutase (SOD), catalase and glyoxalase I (GLO). Glycemia levels also were determined. RESULTS: Our present study has shown an increase in carbonyl content from diabetic rats subjected to FST (2.04 ± 0.55), while the activity of catalase (51.83 ± 19.02) and SOD (2.30 ± 1.23) were significantly decreased in liver from these animals, which were reverted by the treatment. Also, the activity of GLO (0.15 ± 0.02) in the liver of the animals was decreased. DISCUSSION AND CONCLUSION: Our findings showed that insulin plus CNZ acute treatment ameliorate the antioxidant redox parameters and protect against protein oxidative damage in the liver of diabetic rats subjected to FST.

Effects of neonatal dopaminergic lesion on oral cocaine self-administration in rats: Higher female vulnerability to cocaine consumption.

The dopaminergic system is associated with cocaine-seeking behaviors, being influenced by other neurotransmitters such as GABA and deregulated by chronic cocaine self-administration. Administration of 6-hydroxydopamine (6-OHDA) to neonatal rats produces a depletion of brain dopamine, mainly, that results in behavioral alterations in adulthood. This model can be applied to better understanding of the role of the dopaminergic system in cocaine use and how its behavioral effects can modulate drug intake. Though there are well-established sex differences in the pattern of drug use, there are no published studies investigating sex-dependent effects of neonatal lesions with 6-OHDA on cocaine self-administration nor regarding GABAA receptor (GABAAR) subunits expression. Herein, neurotoxic lesion was induced in male and female neonatal rats by intracisternal injection of 6-OHDA at PND 4, and locomotion was evaluated before and after cocaine self-administration. Cocaine was diluted in a sweet solution (sucrose 1.5%) and offered for 27 consecutive 3-h daily sessions via a dispenser for oral intake, in an operant chamber under a fixed-ratio 1 (FR1) schedule. The 6-OHDA lesion reduced oral cocaine self-administration in male and female rats. Female rats, independent of dopaminergic condition, consumed more cocaine-containing solution than sucrose-only solution. Furthermore, as expected, 6-OHDA-lesioned animals presented a higher basal locomotor activity when compared to sham rats. We evaluated GABAAR subunit expression and found no statistically significant differences between rats that self-administered a sucrose-only solution and those that self-administered a cocaine-containing solution. Even when the reward system is depleted, some behavioral differences remain in females, providing more data that highlight the female vulnerability to cocaine consumption.

[Telephone counseling for young users of crack cocaine]. / Aconselhamento telefônico para jovens usuários de crack.

This study seeks to evaluate the use of Brief Motivational Intervention in a telephone counseling service offered to young people in the process of cessation of crack cocaine use. A descriptive study was conducted based on a survey of the records of callsfrom users during the period January 2006 to December 2007. The researchers included 40 recordsfrom calls of young people aged between 16 and 24 years who consumed crack cocaine, associated or not with other substances. At the end of the six-month follow up, 65% of youths had stopped the consumption of crack cocaine. Of the total, 57.5% were in stage of preparation and action on the first call. The chances of relapse to crack cocaine use were higher in follow-ups to 30 days. The conclusion suggests that the association of IBM with telephone counseling is an important treatment option in cessation of crack cocaine use.

A clinical trial on a brief motivational intervention in reducing alcohol consumption under a telehealth supportive counseling.

It is known that among those seeking to cease consumption of alcohol, there can be as high as a 50% relapse rate in the first 12 months. Different tools for treatments have been developed, such as telehealth, with the aim of helping this population. As a result of this demand, technology has gained strength in recent years. A new point of view about the treatment will broaden our knowledge far beyond just efficacy. It seems that understanding the mechanisms that lead to treatment success is as important as knowing its effectiveness. Therefore, the present study examined the relationships between Brief Motivational Intervention by telephone (BMI), motivational stage, outcome, and coping strategies using path analysis. In the post-evaluation, variables such as BMI (randomized individuals), motivational stage and decreased consumption of alcohol reached statistical significance (p<.001), suggesting that BMI might improve motivational stage and reduced consumption of alcohol. In terms of coping, the results also indicate that positive thinking might be a variable of interest when planning to decrease alcohol consumption. More research is needed to recognize the potential of new technology in the health area and to uncover the innumerable possibilities of using these tools as a strategy to help alcohol users.

The impact of chronic exposure to air pollution over oxidative stress parameters and brain histology.

Air pollution (AP) triggers neuroinflammation and lipoperoxidation involved in physiopathology of several neurodegenerative diseases. Our study aims to investigate the effect of chronic exposure to ambient AP in oxidative stress (OS) parameters and number of neurons and microglial cells of the cortex and striatum. Seventy-two male Wistar rats were distributed in four groups of exposure: control group (FA), exposed throughout life to filtered air; group PA-FA, pre-natal exposed to polluted air until weaning and then to filtered air; group FA-PA, pre-natal exposed to filtered air until weaning and then to polluted air; and group PA, exposed throughout life to polluted air. After 150 days of exposure, the rats were euthanized for biochemical and histological determinations. The malondialdehyde concentration in the cortex and striatum was significantly higher in the PA group. The activity of superoxide dismutase was significantly decreased in the cortex of all groups exposed to AP while activity of catalase was not modified in the cortex or striatum. The total glutathione concentration was lower in the cortex and higher in the striatum of the FA-PA group. The number of neurons or microglia in the striatum did not differ between FA and PA. On the other hand, neurons and microglia cell numbers were significantly higher in the cortex of the FA-PA group. Our findings suggest that the striatum and cortex have dissimilar thresholds to react to AP exposure and different adaptable responses to chronically AP-induced OS. At least for the cortex, changing to a non-polluted ambient early in life was able to avoid and/or reverse the OS, although some alterations in enzymatic antioxidant system may be permanent. As a result, it is important to clarify the effects of AP in the cortical organization and function because of limited capacity of brain tissue to deal with threatening environments.

Cocaine reverses the changes in GABAA subunits and in glutamic acid decarboxylase isoenzymes mRNA expression induced by neonatal 6-hydroxydopamine.

Attention-deficit/hyperactivity disorder is related to altered functions in the dopaminergic and GABAergic pathways of cortical and subcortical brain areas The hyperactivity of attention-deficit/hyperactivity disorder is commonly modelled in rats after neonatal lesion with 6-hydroxydopamine (6-OHDA), and amphetamines are effective in reducing hyperactivity in this animal model. Our objectives were to evaluate whether cocaine reverses the motor hyperactivity of 6-OHDA-lesioned rats and to verify cocaine effects in altered mRNA expression of alpha2, alpha4, beta1 and beta2-GABAA subunits and GAD isoenzymes in the prefrontal cortex, hippocampus and striatum of 6-OHDA-lesioned rats. On PND4, 6-OHDA-lesioned or sham rats received 6-OHDA (100 microg intracisternal) or vehicle. Cocaine solution (0.1 mg/ml/day) was offered when adult for 23 days, using the two-bottle choice procedure. The subjects were evaluated in an open-field on the last day of cocaine treatment. 6-OHDA-lesioned rats showed increased locomotion and this hyperactivity was reversed during cocaine self-administration. 6-OHDA lesion caused an increase in the mRNA expression of GABAA subunits in specific brain areas and GAD isoenzymes in the hippocampus and striatum. Increased GAD65 and decreased GAD67 mRNA expression were also shown in the prefrontal cortex. Cocaine self-administration attenuated the effects of 6-OHDA lesions on the mRNA expression of alpha2-GABAA and beta2-GABAA subunits in the prefrontal cortex, reversed the mRNA expression of alpha2-GABAA subunits in the striatum and of alpha4-GABAA subunits in the prefrontal cortex and in the hippocampus, and reversed the mRNA expression of GAD65 and GAD67 in the brain areas studied. Our findings suggest that cocaine reverses some mRNA changes of GABAA subunits and GAD isoenzymes in reward circuits and the behavioural hyperactivity caused by 6-OHDA lesion.

Hippocampus lipid peroxidation induced by residual oil fly ash intranasal instillation versus habituation to the open field.

Epidemiological studies have demonstrated the adverse effects of particulate matter (PM) inhalation on the respiratory and cardiovascular systems. It has been reported that air pollution may affect the central nervous system and decrease cognitive function. In rats, residual oil fly ash (ROFA) instillation causes decreased motor activity and increased lipid peroxidation in the striatum and the cerebellum. Our objective was to determine whether chronic instillation of particles induces changes in learning and memory in rats and whether oxidants in the hippocampus may contribute to these adverse effects. Forty-five-day-old male Wistar rats were exposed to ROFA by intranasal instillation and were treated with N-acetylcysteine (NAC) at 150 mg/kg i.p. for 30 days. Control groups were exposed to ROFA, NAC, or neither. On days 1, 8, and 30 of the protocol, rats were submitted to the open field test to evaluate habituation. After the last open field session, the rats were killed by decapitation. The hippocampus was used to determine lipid peroxidation (LP) by the thiobarbituric acid-reactive substances test. ROFA instillation induced an increase in LP in the hippocampus compared to all treatment groups (p = .012). NAC treatment blocked these changes. All of the treatment groups presented a decrease in the frequency of peripheral walking (p = .001), rearing (p = .001), and exploration (p = .001) over time. Our study demonstrates that exposure to particles for 30 days and/or NAC treatment do not modify habituation to an open field, a simple form of learning and memory in rats, and that oxidative damage induced by ROFA does not modulate these processes.

Protein and lipid oxidative damage in streptozotocin-induced diabetic rats submitted to forced swimming test: the insulin and clonazepam effect.

Diabetes may modify central nervous system functions and is associated with moderate cognitive deficits and changes in the brain, a condition that may be referred to as diabetic encephalopathy. The prevalence of depression in diabetic patients is higher than in the general population, and clonazepam is being used to treat this complication. Oxidative stress may play a role in the development of diabetes complications. We investigated oxidative stress parameters in streptozotocin-induced diabetic rats submitted to forced swimming test (STZ) and evaluated the effect of insulin (STZ-INS) and/or clonazepam (STZ-CNZ and STZ-INS-CNZ) acute treatment on these animal model. Oxidative damage to proteins measured as carbonyl content in plasma was significantly increased in STZ group compared to STZ treated groups. Malondialdehyde plasma levels were significantly reduced in STZ-INS and STZ-INS-CNZ groups when compared to STZ rats, being significantly reduced in STZ-INS-CNZ than STZ-INS rats. The activities of the antioxidant enzymes catalase, superoxide dismutase and glutathione peroxidase showed no significant differences among all groups of animals. These findings showed that protein and lipid damage occurs in this diabetes/depression animal model and that the associated treatment of insulin and clonazepam is capable to protect against oxidative damage in this experimental model.

The role of allopregnanolone in depressive-like behaviors: Focus on neurotrophic proteins.

Allopregnanolone (3α,5α-tetrahydroprogesterone; pharmaceutical formulation: brexanolone) is a neurosteroid that has recently been approved for the treatment of postpartum depression, promising to fill part of a long-lasting gap in the effectiveness of pharmacotherapies for depressive disorders. In this review, we explore the experimental research that characterized the antidepressant-like effects of allopregnanolone, with a particular focus on the neurotrophic adaptations induced by this neurosteroid in preclinical studies. We demonstrate that there is a consistent decrease in allopregnanolone levels in limbic brain areas in rodents submitted to stress-induced models of depression, such as social isolation and chronic unpredictable stress. Further, both the drug-induced upregulation of allopregnanolone or its direct administration reduce depressive-like behaviors in models such as the forced swim test. The main drugs of interest that upregulate allopregnanolone levels are selective serotonin reuptake inhibitors (SSRIs), which present the neurosteroidogenic property even in lower, non-SSRI doses. Finally, we explore how these antidepressant-like behaviors are related to neurogenesis, particularly in the hippocampus. The protagonist in this mechanism is likely the brain-derived neurotrophic factor (BFNF), which is decreased in animal models of depression and may be restored by the normalization of allopregnanolone levels. The role of an interaction between GABA and the neurotrophic mechanisms needs to be further investigated.

The effects of caffeine on alcohol oral self-administration behavior in rats.

Caffeine and alcohol are some of the most commonly used psychoactive substances in the world, and are often used concomitantly. However, little is known about the effect of caffeine on alcohol consumption. Here, our aim was to investigate the co-exposure of alcohol mixed with caffeine in self-administration. Thirty-two male and thirty-two female Wistar rats were randomly divided into the following groups: control, caffeine (0.25 mg/mL), alcohol (10% v/v) and alcohol mixed with caffeine. After one week of training, the animals underwent self-administration for 21 days (1 h per day) in a fixed ratio of 1 (FR1). The forced swimming test (FST) was performed before the training phase and 24 h after the last self-administration session to verify abstinence-induced depressive-like behaviors. Our results showed that all rats consumed a lower volume of alcohol-containing solution than control solution, and that the presence of caffeine did not influence this parameter. Females consumed less volume of alcohol solution than males but the average dose was similar. Females that self-administered alcohol mixed with caffeine presented a higher immobility in the FST than males that self-administered the same solution. These results support the conclusion that moderate doses of caffeine such as the ones from our study (approximately 7-8 mg/kg/day) do not influence alcohol consumption. Additionally, females might be more susceptible than males to depressive-like effects caused by the abstinence of the use of these substances in combination.

Hemisphere-dependent Changes in mRNA Expression of GABAA Receptor Subunits and BDNF after Intra-prefrontal Cortex Allopregnanolone Infusion in Rats.

Allopregnanolone is a neurosteroid implicated in mood disorders such as depression and anxiety. It acts as a GABAA receptor (GABAAR)-positive allosteric modulator and changes the expression of GABAAR subunits and of brain-derived neurotrophic factor (BDNF) in different brain regions. It has been demonstrated that such neurochemical changes may have an asymmetrical pattern regarding brain hemispheres. The aim of this study was to verify the behavioral and hemisphere-specific neurochemical effects of the bilateral intra-prefrontal cortex (intra-PFC) infusion of allopregnanolone in rats. Rats were exposed to the forced swim test and to the grooming microstructure test, followed by the right and left hemisphere-specific quantification of mRNA expression by Real-Time PCR of δ and γ2 GABAAR subunits and BDNF in the PFC and in the hippocampus. Though we did not observe any significant effects in the behavioral tests, intra-PFC allopregnanolone infusion bilaterally increased the mRNA expression of the δ subunit in the same area and of BDNF in the hippocampus. Both mRNA expressions of the γ2 subunit and BDNF were higher in the right than in the left PFC of control animals, and the hemisphere differences were not seen after allopregnanolone infusion. Overall hippocampal BDNF expression was also higher in the right hemisphere, but this asymmetry was not normalized by allopregnanolone. No asymmetries or changes were observed in the hippocampal mRNA expression of GABAAR subunits. These results point to a hemisphere-dependent regulation of GABAAR subunits and BDNF that can be modulated by intra-PFC allopregnanolone infusion, even in the absence of associated behavioral effects.

Role of Parenting Styles in Adolescent Substance Use Cessation: Results from a Brazilian Prospective Study.

BACKGROUND: This study aims to identify the association between parenting styles and behavioral changes among adolescents regarding the consumption of alcohol, tobacco, cannabis, cocaine/crack. METHODS: A group of ninety-nine adolescents (39 girls and 60 boys), aged 14 to 19 years (17.05 ± 1.51), who called in to a call center that provides counseling to substance users, was followed-up for 30 days. Data collection occurred between March 2009 and October 2015. The adolescents answered questions regarding parental responsiveness and demanding nature on a scale to assess parental styles and provided sociodemographic data, substance abuse consumption characteristics, and the Contemplation Ladder scale score. RESULTS: The parental styles most reported by the adolescents were authoritative (30%) and indulgent (28%). Children who perceived their mothers as having an indulgent style and who had absent fathers presented more difficulties in making behavioral changes to avoid alcohol and cocaine/crack consumption. CONCLUSION: The study found that parent-child relationships were associated with a lack of change in the adolescent regarding substance use behavior, particularly the consumption of alcohol and cocaine/crack.

The effect of intracerebroventricular allopregnanolone on depressive-like behaviors of rats selectively bred for high and low immobility in the forced swim test.

Depression is a highly incapacitating disorder known to have a multifactorial etiology, including a hereditary genetic background. The neurosteroid allopregnanolone (ALLO) is a positive allosteric modulator of the GABAA receptor and has been shown to have an antidepressant-like effect in animals. This study aimed to assess the behavioral effect of ALLO in animals with different backgrounds of depressive-like activity. An initial population (F0) of male and female Wistar rats was screened for immobility behavior utilizing the Forced Swim Test (FST). Rats with extreme immobility scores were selected for either the High Immobility (HI) group or the Low Immobility (LI) group for breeding, giving origin to the subsequent generations F1 and F2. Guide cannulas were implanted in the lateral ventricle of F2 males for intracerebroventricular infusions of 5 µg/rat of ALLO, 5 µg/rat of imipramine (IMI) or vehicle (CTR), which occurred 24, 5 and 1 h prior to the test session of the drug FST. In the pre-drug FST, a statistically significant difference was observed between the immobility scores from the HI and LI groups of F2 rats. HI rats from F2 also showed significantly higher immobility time when compared to F0. In these HI animals, both IMI and ALLO significantly reduced immobility when compared to the CTR group. IMI-treated rats also showed lower immobility than the ALLO group. In the LI rats, no difference in immobility was found between treatments. In conclusion, two strains of rats with significantly different immobility profiles in the FST were obtained in a relatively short time, after only two generations. Infusions of both ALLO and IMI showed a strain-dependent antidepressant-like effect, being detected in the HI animals but not in the LI animals, which is in line with the clinical understanding that antidepressants have higher efficacy in more severe forms of depression.

Environmental enrichment reduces cocaine neurotoxicity during cocaine-conditioned place preference in male rats.

Environmental enrichment (EE) has a neuroprotective role and prevents the development of cocaine addiction behavior in rats. Studies showing the role of EE in cocaine toxicity are nonexistent. We hypothesized that rats exposed to EE are protected from cocaine-induced changes in the redox profile and DNA damage after undergoing conditioned place preference (CPP). Ten male Wistar rats were placed in EE cages equipped with toys, a ladder and tunnels, and ten were provided clean, standard laboratory housing (non-EE). EE and non-EE rats were randomly allocated to the classical CPP cocaine vs. saline (COC/Saline) group, where cocaine (15 mg/kg; i.p.) was tested alternately with saline. Afterwards, intracellular reactive species and antioxidant enzymes were evaluated and the comet essay was performed in the prefrontal cortex and hippocampus of rats. As expected, EE rats spent less time in the cocaine-paired chamber, and as a new result, less cocaine-induced DNA damage was observed in the two brain structures. Altogether, our results demonstrate that EE decreases neurotoxicity in brain regions linked to cocaine addiction but does not extinguish it completely.