Adolescent exposure to cocaine increases anxiety-like behavior and induces morphologic and neurochemical changes in the hippocampus of adult rats

Development of anxiety-like behaviors during adolescence: Persistent effects of adolescent morphine exposure in male rats

Epidemiological studies show the prevalence of opioid use, misuse and abuse in adolescents, which imposes social and economic accountability worldwide. Chronic opioid exposure, especially in adolescents, may have lasting effects on emotional behaviors that persist into adulthood. The current experiments were therefore designed to study the effects of sustained opioid exposure during adolescence on anxiety-like behaviors. Adolescent male Wistar rats underwent increasing doses of morphine for 10 days (PNDs 31-40). After that the open field test (OFT) and elevated plus maze (EPM) test were performed over a 4-week postmorphine treatment from adolescence to adulthood. Moreover, the weight of the animals was measured at these time points. We found that chronic adolescent morphine exposure reduces the weight gain during the period of morphine treatment and 4 weeks after that. It had no significant effect on the locomotor activity in the animals. Moreover, anxiolytic-like behavior was observed in the rats exposed to morphine during adolescence evaluated by OFT and EPM test. Thus, long-term exposure to morphine during adolescence has the profound potential of altering the anxiety-like behavior profile in the period from adolescence to adulthood. The maturation of the nervous system can be affected by drug abuse during the developmental window of adolescence and these effects may lead to behaviorally stable alterations.

Substance use, microbiome and psychiatric disorders

Accumulating evidence from several studies has shown association between substance use, dysregulation of the microbiome and psychiatric disorders such as depression, anxiety, and psychosis. Many of the abused substances such as cocaine and alcohol have been shown to alter immune signaling pathways and cause inflammation in both the periphery and the central nervous system (CNS). In addition, these substances of abuse also alter the composition and function of the gut microbiome which is known to play important roles such as the synthesis of neurotransmitters and metabolites, that affect the CNS homeostasis and consequent behavioral outcomes. The emerging interactions between substance use, microbiome and CNS neurochemical alterations could contribute to the development of psychiatric disorders. This review provides an overview of the associative effects of substance use such as alcohol, cocaine, methamphetamine, nicotine and opioids on the gut microbiome and psychiatric disorders involving anxiety, depression and psychosis. Understanding the relationship between substance use, microbiome and psychiatric disorders will provide insights for potential therapeutic targets, aimed at mitigating these adverse outcomes.

O‑GlcNAcylation contributes to intermittent hypoxia‑associated vascular dysfunction via modulation of MAPKs but not CaMKII pathways

Intermittent hypoxia (IH) leads to vascular dysfunction, and O-linked-β-N-acetylglucosamine (O-GlcNAc)ylation may regulate vascular reactivity through the modulation of intracellular signaling. The present study hypothesized that O-GlcNAc modifications contributed to the vascular effects of acute IH (AIH) and chronic IH (CIH) through the MAPK and Ca²⁺/calmodulin-dependent kinase II (CaMKII) pathways. Rat aortic and mesenteric segments were incubated with DMSO, O-GlcNAcase (OGA) or O-GlcNAc transferase (OGT) inhibitor under either normoxic or AIH conditions for 3 h, and arterial function was then assessed. Meanwhile, arteries isolated from control and CIH rats were exposed to 3 h of incubation under normoxic conditions using DMSO, OGA or OGT as an inhibitor, before assessing arterial reactivity. CIH was found to increase the expression of vascular O-GlcNAc protein and OGT, phosphorylate p38 MAPK and ERK1/2, and decrease OGA levels, but it had no effects on phosphorylated CaMKII levels. OGA inhibition increased global O-GlcNAcylation and the phosphorylation of p38 MAPK, ERK1/2 and CaMKII, whereas OGT blockade had the opposite effects. OGA inhibition preserved acetylcholine-induced relaxation in AIH arteries, whereas OGT blockade attenuated the relaxation responses of arteries under normoxic conditions or undergoing AIH treatments. However, the impairment of acetylcholine dilation in CIH mesenteric arteries was improved. CIH artery contraction was increased following angiotensin II (Ang II) exposure. Blockade of p38 MAPK and ERK1/2, but not CaMKII, attenuated Ang II-induced contractile responses in CIH arteries isolated from the non-OGT inhibitor-treated groups. OGT inhibition significantly blocked contractile responses to Ang II and abolished the inhibitory effects of MAPK inhibitors. These findings indicated that O-GlcNAcylation regulates IH-induced vascular dysfunction, at least partly by modulating MAPK, but not CaMKII, signaling pathways.

Oxandrolone treatment in juvenile rats induced anxiety-like behavior in young adult animals

AIMS

Oxandrolone (OXA) is a synthetic steroid used for the treatment of clinical conditions associated with catabolic states in humans, including children. However, its behavioral effects are not well known. Our goal was to evaluate the anxiety-like behavior induced in young adult rats after the treatment of juvenile animals with OXA.

METHODS

Four-week-old male rats were separated into three groups: Control (CON), therapeutic-like OXA dose (TD), and excessive OXA dose (ED), in which 2.5 and 37.5 mg/kg/day of OXA were administered via gavage for four weeks for TD and ED, respectively. Behavior was evaluated through the elevated plus maze (EPM) and open field (OF) tests. Protein expression of catalase (CAT), superoxide dismutase (SOD), Tumor necrosis factor-α (TNF-α), and dopamine receptor 2 (DrD2) were analyzed in tissue samples of the hippocampus, amygdala, and prefrontal cortex by Western Blot.

RESULTS

OXA induced anxiety-like behaviors in both TD and ED animals; it decreased the time spent in the open arms of the EPM in both groups and reduced the time spent in the central zone of the OF in the TD group. In the hippocampus, CAT expression was higher in TD compared with both control and ED animals. No differences were found in the amygdala and prefrontal cortex. TNF-α, SOD, and DrD2 levels were not altered in any of the assessed areas.

CONCLUSIONS

Treatment of juvenile rats with OXA led to anxiety-like behavior in young adult animals regardless of the dose used, with minor changes in the antioxidant machinery located in the hippocampus.

The effects of cocaine exposure in adolescence: Behavioural effects and neuroplastic mechanisms in experimental models

Drug addiction is a devastating disorder with a huge economic and social burden for modern society. Although an individual may slip into drug abuse throughout his/her life, adolescents are at higher risk, but, so far, only a few studies have attempted to elucidate the underlying cellular and molecular bases of such vulnerability. Indeed, preclinical evidence indicates that psychostimulants and adolescence interact and contribute to promoting a dysfunctional brain. In this review, we have focused our attention primarily on changes in neuroplasticity brought about by cocaine, taking into account that there is much less evidence from exposure to cocaine in adolescence, compared with that from adults. This review clearly shows that exposure to cocaine during adolescence, acute or chronic, as well as contingent or non‐contingent, confers a vulnerable endophenotype, primarily, by causing changes in neuroplasticity. Given the close relationship between drug abuse and psychiatric disorders, we also discuss the translational implications providing an interpretative framework for clinical studies involving addictive as well as affective or psychotic behaviours.

Maternal crack cocaine use in rats leads to depressive- and anxiety-like behavior, memory impairment, and increased seizure susceptibility in the offspring

Crack users suffer the effects of cocaine present in the drug and the action of other active compounds from its pyrolysis. An emergent fact is an increase in the number of pregnant crack cocaine users. Studies suggest that crack cocaine and its metabolites cross the placenta, promoting premature birth, fever, irritability, sweating, and seizures in the early months of life. In children, the effects of crack cocaine have been associated with cognitive deficits, difficulty in verbalization, aggressiveness, and depression, besides enhancing the susceptibility to epileptic seizures, including status epilepticus (SE) in adulthood. Therefore, we investigated the effect of maternal exposure to smoke crack cocaine on several behavioral parameters in the offspring during adulthood. A series of behavioral tests and intrahippocampal pilocarpine (H-PILO) microinjection at sub-convulsive and convulsive doses in a rat model demonstrated that exposure to crack cocaine during the embryonic period leads to anxiogenic-like behavior and long-term memory impairment in both genders and promotes depressive-like behavior in the female. Besides, crack cocaine offspring exposed to a sub-convulsive H-PILO dose showed higher susceptibility to SE, increased seizure frequency, and neurodegeneration, while animals that received a convulsive dose of H-PILO displayed no alteration in SE severity. Taken together, our data suggest that crack cocaine exposure during the gestational period leads to an increased predilection for anxiety and depression, long-term memory deficits, and reduction in the threshold for developing epileptic seizures associated with neuronal death, which predispose crack cocaine babies to develop neuropsychological disorders.

Remote memory of drug experiences coexists with cognitive decline and abnormal adult neurogenesis in an animal model of cocaine-altered cognition

Cocaine addiction is a chronic disorder in which the person loses control over drug use. The past memories of the stimuli associated with the drug are a relevant clinical problem, since they trigger compulsive drug-seeking and drug-taking habits. Furthermore, these persistent drug-related memories seemingly coexist with cognitive decline that predicts worse therapeutic output. Here, we use a new animal model of cocaine-altered cognition that allowed to observe these events in the same individual and study their relationship. Mice were chronically administered cocaine in a conditioned place preference (CPP) apparatus for 14 days, and control mice received saline. After 28 days of cocaine withdrawal, animals were tested for retrieval of remote drug-associated memory as well as for cognitive performance in a battery of tests, including novel object and place recognition and spatial memory. The cocaine-withdrawn mice showed persistent CPP memory while impaired in the cognitive tasks, displaying deficits in reference memory acquisition and working memory. However, the CPP expression was not associated with the defective cognitive performance, indicating that they were concomitant but independent occurrences. After completion of the experiment, adult hippocampal neurogenesis (AHN) was studied as a relevant neurobiological correlate due to its potential role in both learning and drug addiction. Results suggested a preserved basal AHN in the cocaine-withdrawn mice but an aberrant learning-induced regulation of these neurons. This paradigm may be useful to investigate maladaptive cognition in drug addiction as well as related therapies.

Increased negative affect when combining early-life maternal deprivation with adolescent, but not adult, cocaine exposure in male rats: regulation of hippocampal FADD

RATIONALE

Besides early drug initiation during adolescence, another vulnerability factor associated with increased risk for substance abuse later in life is early-life stress. One way of assessing such combined risk is by evaluating the emergence of increased negative affect during withdrawal (i.e., linked to persistence in drug seeking).

OBJECTIVES

To compare the impact of maternal deprivation with cocaine exposure at different ages on affective-like behavior and hippocampal neuroplasticity regulation.

METHODS

Maternal deprivation was performed in whole-litters of Sprague-Dawley rats (24 h, PND 9-10). Cocaine (15 mg/kg, 7 days, i.p.) was administered in adolescence (PND 33-39) or adulthood (PND 64-70). Changes in affective-like behavior were assessed by diverse tests across time (forced-swim, open field, novelty-suppressed feeding, sucrose preference). Hippocampal multifunctional FADD protein (balance between cell death and plasticity) was evaluated by Western blot.

RESULTS

Exposing rats to either maternal deprivation or adolescent cocaine did not modulate affective-like behavior immediately during adolescence, but increased negative affect in adulthood. Maternal deprivation combined with adolescent cocaine advanced the negative impact to adolescence. Adult cocaine exposure alone and/or in combination with maternal deprivation did not induce any behavioral changes at the time-points analyzed. FADD regulation might participate in the neural adaptations taking place in the hippocampus in relation to the observed behavioral changes.

CONCLUSIONS

Adolescence is a more vulnerable period, as compared to adulthood, to the combined impact of cocaine and early maternal deprivation, thus suggesting that the accumulation of stress early in life can anticipate the negative behavioral outcome associated with drug consumption.

Neurobehavioral changes arising from early life dopamine signaling perturbations

Dopamine (DA) signaling is critical to the modulation of multiple brain functions including locomotion, reinforcement, attention and cognition. The literature provides strong evidence that altered DA availability and actions can impact normal neurodevelopment, with both early and enduring consequences on anatomy, physiology and behavior. An appreciation for the developmental contributions of DA signaling to brain development is needed to guide efforts to preclude and remedy neurobehavioral disorders, such as attention-deficit/hyperactivity disorder, addiction, bipolar disorder, schizophrenia and autism spectrum disorder, each of which exhibits links to DA via genetic, cellular and/or pharmacological findings. In this review, we highlight research pursued in preclinical models that use genetic and pharmacological approaches to manipulate DA signaling at sensitive developmental stages, leading to changes at molecular, circuit and/or behavioral levels. We discuss how these alterations can be aligned with traits displayed by neuropsychiatric diseases. Lastly, we review human studies that evaluate contributions of developmental perturbations of DA systems to increased risk for neuropsychiatric disorders.

Adolescent drug exposure: A review of evidence for the development of persistent changes in brain function

Over the past decade, many studies have indicated that adolescence is a critical period of brain development and maturation. The refinement and maturation of the central nervous system over this prolonged period, however, makes the adolescent brain highly susceptible to perturbations from acute and chronic drug exposure. Here we review the preclinical literature addressing the long-term consequences of adolescent exposure to common recreational drugs and drugs-of-abuse. These studies on adolescent exposure to alcohol, nicotine, opioids, cannabinoids and psychostimulant drugs, such as cocaine and amphetamine, reveal a variety of long-lasting behavioral and neurobiological consequences. These agents can affect development of the prefrontal cortex and mesolimbic dopamine pathways and modify the reward systems, socio-emotional processing and cognition. Other consequences include disruption in working memory, anxiety disorders and an increased risk of subsequent drug abuse in adult life. Although preventive and control policies are a valuable approach to reduce the detrimental effects of drugs-of-abuse on the adolescent brain, a more profound understanding of their neurobiological impact can lead to improved strategies for the treatment and attenuation of the detrimental neuropsychiatric sequelae.

Combined neurotoxic effects of cannabis and nandrolone decanoate in adolescent male rats

Polydrug use among adolescence is a widespread phenomenon and has increased in the last few years. In particular, most nandrolone decanoate (Nan) abusers combine its use with cannabis (Can); thus, studying the consequences of this combination in adolescent subjects is important because potentiation of their effects may increase their neurotoxicity. The present study was designed to study the neurotoxic effects of Nan and Can, alone and in combination, in adolescent male rats by studying the behavioural, biochemical, and histopathological effects. Nan (15 mg/kg, s.c.) and Can (20 mg/kg, s.c.) were given alone or in combination to rats once daily for one month. The combined administration of Can and Nan induced learning and spatial memory deficits, hypo-locomotion, anxiety and aggression in adolescent rats as evidenced by the Morris water maze, open field, elevated plus maze, and defensive aggression tests. In parallel, rats treated with the combination showed severe deleterious effects in the hippocampal and prefrontal cortex (PFC) neural architecture along with a decrease in brain-derived neurotropic factor. Furthermore, combined administration of Can and Nan increased oxidative stress (significantly increased malondialdehyde and nitric oxide levels and reduced glutathione content), elevated brain pro-inflammatory cytokines (tumour necrosis factor alpha and interleukin 1 beta), and upregulated caspase-3, caspase-8, and caspase-9 mRNA expression and cytochrome c levels. In conclusion, abuse of both Can and Nan conferred greater neurotoxic effects than either drug alone that were at least partially attributed to oxidative stress, inflammation, and intrinsic and extrinsic apoptosis in the hippocampus and PFC of rats.

Cocaine-induced changes in CX3CL1 and inflammatory signaling pathways in the hippocampus: Association with IL1β

Cocaine induces neuroinflammatory response and interleukin-1 beta (IL1β) is suggested a final effector for many cocaine-induced inflammatory signals. Recently, the chemokine fractalkine (CX₃CL1) has been reported to regulate hippocampus-dependent neuroinflammation and synaptic plasticity via CX₃C-receptor 1 (CX₃CR1), but little is known about the impact of cocaine. This study is mainly focused on the characterization of CX₃CL1, IL1β and relevant inflammatory signal transduction pathways in the hippocampus in acute and repeated cocaine-treated male mice. Complementarily, the rewarding properties of cocaine were also assessed in Cx3cr1-knockout (KO) mice using a conditioned place preference (CPP). We observed significant increases in CX₃CL1 and IL1β concentrations after cocaine, although repeated cocaine produced an enhancement of CX₃CL1 concentrations. CX₃CL1 and IL1β concentrations were positively correlated in acute (r = +0.61) and repeated (r = +0.82) cocaine-treated mice. Inflammatory signal transduction pathways were assessed. Whereas acute cocaine-treated mice showed transient increases in p-ERK1/2/ERK1/2 and p-p65/p65 NFκB ratios after cocaine injection, repeated cocaine-treated mice showed transient increases in p-ERK1/2/ERK1/2, p-p38/p38 MAPK, p-NFκB p65/NF-κB p65 and p-CREB/CREB ratios. Baseline p-p38/p38 MAPK and p-CREB/CREB ratios were downregulated in repeated cocaine-treated mice. Regarding the cocaine-induced CPP, Cx3cr1-KO mice showed a notably impaired extinction but no differences during acquisition and reinstatement. These results indicate that cocaine induces alterations in CX₃CL1 concentrations, which are associated with IL1β concentrations, and activates convergent inflammatory pathways in the hippocampus. Furthermore, the CX₃CL1/CX₃CR1 signaling could mediate the processes involved in the extinction of cocaine-induced CPP.

Cocaine treatment before pregnancy differentially affects the anxiety and brain glucose metabolism of lactating rats if performed during adulthood or adolescence

Cocaine exposure disrupts the maternal behavior of lactating rats, yet it is less known whether it alters the affective changes that accompany motherhood. As the long-term action of cocaine on anxiety varies according to the developmental stage of the individuals, this study aimed to compare the effect of a chronic treatment with cocaine to adult and adolescent non-pregnant females on their anxiety-like behavior and basal brain metabolic activity during lactation. Thus, adult and adolescent virgin rats were exposed to cocaine (0.0 or 15.0 mg/kg ip) during 10 days and were mated four days later. Anxiety behavior was evaluated on postpartum days 3-4 in the elevated plus maze test, and the basal brain glucose metabolism was determined on postpartum days 7-9 by means of [¹⁸F] fluorodeoxyglucose positron emission tomography. Cocaine treatment during adulthood increased the anxiety-like behavior of lactating females whereas its administration during adolescence decreased it. Also, the basal glucose metabolism of the medial prefrontal cortex differed between lactating females treated with cocaine during adulthood and adolescence. These differential effects of cocaine, according to the age at which the drug was administered, support the idea that the adolescent and adult brains have a distinct susceptibility to this drug, which leads to divergent long-term changes in the neural circuits that regulate anxiety during lactation.

Adolescent cocaine exposure enhances the GABAergic transmission in the prelimbic cortex of adult mice

We have recently shown in rats that adolescent cocaine exposure induces prolonged modifications on synapses in medial prefrontal cortex (mPFC), which might contribute to long-term behavioral outcomes in adulthood. In this study, we further investigated the molecular mechanisms underlying adolescent cocaine exposure-related psychiatric problems in adulthood, especially focusing on the alterations of GABAergic transmission in prelimbic cortex (PrL), 1 subregion of mPFC. Consistent with a previous study, adolescent cocaine-exposed mice exhibited enhanced anxiety-like behaviors in their adulthood. In the same mice models, depression-like behaviors increased as well, but the conditioned place preference formed normally. In parallel, activities of pyramidal neurons at layer V of PrL were reduced after adolescent cocaine exposure, accompanied by an increase in the percentage of symmetric synapses in PrL of adult mice. Additionally, miniature inhibitory postsynaptic currents rather than miniature excitatory postsynaptic currents were increased on these pyramidal neurons, and increased levels of GABA were found in adult PrL. The molecules in the GABAergic system in adult PrL were also changed by adolescent cocaine use, as indicated by increased glutamate decarboxylase 67 kDa, GABA_A-α1, and decreased GABA transporter 1. In the same mice, some regulators to GABAergic transmission such as neuregulin 1/ErbB4 signals were heightened as well. Collectively, these findings revealed that adolescent cocaine exposure results in permanent enhancement of GABAergic transmission on pyramidal neurons in PrL, which subsequently attenuate the activities of these neurons and ultimately contributes to the development of psychiatric disorders in later life.-Shi, P., Nie, J., Liu, H., Li, Y., Lu, X., Shen, X., Ge, F., Yuan, T.-F., Guan, X. Adolescent cocaine exposure enhances the GABAergic transmission in the prelimbic cortex of adult mice.

Short-term withdrawal from repeated exposure to cocaine during adolescence modulates dynorphin mRNA levels and BDNF signaling in the rat nucleus accumbens

BACKGROUND

Early-life stressful events affect the neurobiological maturation of cerebral circuitries including the endogenous opioid system and the effects elicited by adolescent cocaine exposure on this system have been poorly investigated. Here, we evaluated whether cocaine exposure during adolescence causes short- or long-term alterations in mRNAs codifying for selected elements belonging to the opioid system. Moreover, since brain-derived neurotrophic factor (BDNF) may undergo simultaneous alterations with the opioid peptide dynorphin, we also evaluated its signaling pathway as well.

METHODS

Adolescent male rats were exposed to cocaine (20 mg/kg/day) from post-natal day (PND) 28 to PND42, approximately corresponding to human adolescence. After short- (PND45) or long-term (PND90) abstinence, prodynorphin-κ-opioid receptor (pDYN-KOP) and pronociceptin-nociceptin receptor (pN/OFQ-NOP) gene expression were evaluated in the nucleus accumbens (NAc) and hippocampus (Hip) together with the analysis of BDNF signaling pathways.

RESULTS

In the NAc of PND45 rats, pDYN mRNA levels were up-regulated, an effect paralled by increased BDNF signaling. Differently from NAc, pDYN mRNA levels were down-regulated in the Hip of PND45 rats without significant changes of BDNF pathway. At variance from PND45 rats, we did not find any significant alteration of the investigated parameters either in NAc and Hip of PND90 rats.

CONCLUSIONS

Our results indicate that the short-term withdrawal from adolescent cocaine exposure is characterized by a parallel pDYN mRNA and BDNF signaling increase in the NAc. Given the depressive-like state experienced during short abstinence in humans, we hypothesize that such changes may contribute to promote the risk of cocaine abuse escalation and relapse.

Adolescent cocaine exposure enhanced negative affect following drug re-exposure in adult rats: Attenuation of c-Fos activation

BACKGROUND

The goal of the present study was to utilize the adolescent drug experience as an emerging vulnerability factor for developing psychiatric comorbidities in adulthood that could, in turn, help to elucidate and/or hypothesize possible mechanisms contributing to higher relapse rates.

OUTCOMES

The current results showed that adolescent cocaine exposure (15 mg/kg, intraperitoneally, seven days) during early-mid adolescence (postnatal days 33-39) enhanced negative affect in adulthood, by increasing behavioral despair following drug re-exposure and by increasing anhedonia. Thus, these behavioral data provided a good model to further ascertain the long-term cellular and molecular adaptations that might take place in the brain in response to adolescent cocaine exposure as well as the impact of drug re-exposure in adulthood. In this regard, the results showed that adolescent cocaine exposure did not modulate cell proliferation (Ki-67+ cells) or c-Fos protein activation in the dentate gyrus region of the hippocampus, but attenuated c-Fos activation in the dorsal striatum.

CONCLUSIONS

These results proved that a history of cocaine exposure during adolescence increased the vulnerability to induce negative affect (i.e. emergence of psychiatric comorbidity) in adulthood while it decreased neuronal activation in the dorsal striatum. Interestingly, these effects were only observed following cocaine re-exposure in adulthood, suggesting that avoiding drug contact in adulthood could prevent the long-term negative effects induced by adolescent cocaine.

Astroglial correlates of neuropsychiatric disease: From astrocytopathy to astrogliosis

Complex roles for astrocytes in health and disease continue to emerge, highlighting this class of cells as integral to function and dysfunction of the nervous system. In particular, escalating evidence strongly implicates a range of changes in astrocyte structure and function associated with neuropsychiatric diseases including major depressive disorder, schizophrenia, and addiction. These changes can range from astrocytopathy, degeneration, and loss of function, to astrogliosis and hypertrophy, and can be either adaptive or maladaptive. Evidence from the literature indicates a myriad of changes observed in astrocytes from both human postmortem studies as well as preclinical animal models, including changes in expression of glial fibrillary protein, as well as changes in astrocyte morphology and astrocyte-mediated regulation of synaptic function. In this review, we seek to provide a comprehensive assessment of these findings and consequently evidence for common themes regarding adaptations in astrocytes associated with neuropsychiatric disease. While results are mixed across conditions and models, general findings indicate decreased astrocyte cellular features and gene expression in depression, chronic stress and anxiety, but increased inflammation in schizophrenia. Changes also vary widely in response to different drugs of abuse, with evidence reflective of features of astrocytopathy to astrogliosis, varying across drug classes, route of administration and length of withdrawal.

Normal glutathione levels in autopsied brain of chronic users of heroin and of cocaine

BACKGROUND

Animal studies suggest that exposure to either of the two widely used drugs of abuse, heroin or cocaine, causes depletion of the antioxidant, reduced glutathione, a hallmark of oxidative stress, in the brain. However, the relevance of the animal findings to the human is uncertain and clinical trials with the antioxidant GSH precursor n-acetylcysteine have produced mixed results in cocaine dependence.

METHODS

Our major objective was to compare glutathione levels, determined by an HPLC-coulometric procedure, in autopsied brain of chronic heroin (n = 11) and cocaine users (n = 9), who were positive for the drugs in the brain, to those of matched controls (n = 16). Six brain regions were examined, including caudate, hippocampus, thalamus and frontal, temporal and insular cortices.

RESULTS

In contrast to experimental animal findings, we found no statistically significant difference between mean levels of reduced or oxidized glutathione in the drug user vs. control groups. Moreover, no correlation was found between levels of drugs in the brain and those of glutathione.

CONCLUSIONS

Acknowledging the many generic limitations of an autopsied human brain study and the preliminary nature of the findings, our data nevertheless suggest that any oxidative stress caused by heroin or cocaine in chronic users of the drugs might not be sufficient to cause substantial loss of stores of glutathione in the human brain, at least during early withdrawal. These findings, requiring replication, might also have some relevance to future clinical trials employing glutathione supplement therapy as an anti-oxidative strategy in chronic users of the two abused drugs.

Adolescent cocaine exposure induces prolonged synaptic modifications in medial prefrontal cortex of adult rats

Substance used during adolescent period increases the risk of psychiatric disorders in later life, but the underlying neural mechanisms remain unclear. We hypothesize that synaptic remodeling and changes of homeostasis in the medial prefrontal cortex (mPFC) following adolescent cocaine exposure may last for a long time, and these modifications may contribute to behavioral deficiencies in adulthood. To address this hypothesis, rats were exposed to cocaine hydrochloride from postnatal day 28 (P28) to P42. When reared to adulthood, rats were subjected to behavioral tests. On P75 and P76, cocaine-experienced rats exhibited increased locomotive and anxiety-like behaviors, as well as impaired non-selective attention. In the cocaine-experienced rats, both levels of synapse-related proteins (synapsin I and PSD-95) and density of synapse and dendrite spine in mPFC were significantly decreased when compared to controls. Unexpected, the expression of molecules related to oxidative stress, inflammation and apoptosis showed no significant changes in mPFC following adolescent cocaine exposure. These findings suggested that adolescent exposure to cocaine induce long-term modification on synapses in mPFC, which might contribute to long-term behavioral outcomes in adulthood.

Proinflammatory cytokines correlate with early exercise attenuating anxiety-like behavior after cerebral ischemia

Background and Objective

Stroke may cause neuropsychiatric problems, which have negative effects on cognitive functions and behavior. Exercise plays an important role in reducing the occurrence and development of stroke, the concrete mechanism is not fully clarified. In this study, we attempted to determine whether early treadmill exercise attenuates anxiety-like behavior by regulation of inflammation after brain ischemia.

Method

We subjected adult male rats to middle cerebral artery occlusion (MCAO) for 90 min and trained rats started to run on a treadmill from postoperative day 1 to day 14. The effects of treadmill on cognitive functions, anxiety-like behavior, and immune activation were analyzed by Morris water maze test, open field test, elevated plus maze test, and enzyme-linked immunosorbent assay.

Results

Early treadmill exercise significantly improved cognitive function, alleviated anxiety-like behavior in ischemic rats model; this improvement was associated with significantly decreased activation of astrocytes and microglia cells and proinflammatory markers (platelet-activating factor [PAF], interleukin-6 [IL-6], tumor necrosis factor-alpha [TNF-α], intercellular adhesion molecule-1 [ICAM-1], and vascular cell adhesion molecule-1 [VCAM-1]).

Conclusion

Our results indicated that early treadmill exercise attenuated anxiety-like behavior by decreasing inflammation response, exercise conferred a great benefit of attenuating anxiety-like behavior via anti-inflammatory treatment may prove to be a novel neuroprotective strategy for stroke.

Distinct cognitive performance and patterns of drug use among early and late onset cocaine users

INTRODUCTION

Adolescence is a crucial period for neurodevelopment, but few studies have investigated the impact of early cocaine use on cognitive performance and patterns of substance use.

METHODS

We evaluated 103 cocaine dependent inpatients divided in two groups: early-onset users (EOG; n=52), late-onset users (LOG; n=51), and 63 healthy controls. Neuropsychological functioning was evaluated using Digits Forward (DF) and Backward (DB), Trail Making Test (TMT), Stroop Color Word Test (SCWT), Controlled Oral Word Association Test (COWAT), Wisconsin Card Sorting Test (WCST), Rey Osterrieth Complex Figure Test (ROCFT), Frontal Assessment Battery (FAB), and Iowa Gambling Test (IGT). Use of alcohol and other drugs was assessed with the Addiction Severity Index (ASI-6).

RESULTS

Analyses of covariance controlling for age, IQ and years of education showed that EOG presented worse performance in attention span (DF, p=0.020), working memory (DB, p=0.001), sustained attention (WCST, p=0.030), declarative memory (ROCFT, p=0.031) and general executive functioning (FAB, p=0.003) when compared with the control group. LOG presented impairments on divided attention (TMT, p=0.003) and general executive functioning (FAB, p=0.001) in relation to the control group. EOG presented higher use of cannabis and alcohol than LOG (p≤0.001).

CONCLUSION

Early-onset cocaine users display more pronounced neuropsychological alterations than controls, as well as a greater frequency of polydrug consumption than LOG. The prominent cognitive deficits in EOG probably reflect the deleterious interference of cocaine use with early stages of neurodevelopment. This may be related to more severe clinical characteristics of substance disorder in this subgroup, including polysubstance abuse.

Melatonin ameliorates anxiety and depression-like behaviors and modulates proteomic changes in triple transgenic mice of Alzheimer's disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease accompanied by neuropsychiatric symptoms, such as anxiety and depression. The levels of melatonin decrease in brains of AD patients. The potential effect of melatonin on anxiety and depression behaviors in AD and the underlying mechanisms remain unclear. In this study, we treated 10-month-old triple transgenic mice of AD (3xTg-AD) with melatonin (10 mg/kg body weight/day) for 1 month and explored the effects of melatonin on anxiety and depression-like behaviors in 3xTg-AD mice and the protein expression of hippocampal tissues. The behavioral test showed that melatonin ameliorated anxiety and depression-like behaviors of 3xTg-AD mice as measured by open field test, elevated plus maze test, forced swimming test, and tail suspension test. By carrying out two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) coupled with mass spectrometry, we revealed a total of 46 differentially expressed proteins in hippocampus between the wild-type (WT) mice and non-treated 3xTg-AD mice. A total of 21 differentially expressed proteins were revealed in hippocampus between melatonin-treated and non-treated 3xTg-AD mice. Among these differentially expressed proteins, glutathione S-transferase P 1 (GSTP1) (an anxiety-associated protein) and complexin-1 (CPLX1) (a depression-associated protein) were significantly down-regulated in hippocampus of 3xTg-AD mice compared with the WT mice. The expression of these two proteins was modulated by melatonin treatment. Our study suggested that melatonin could be used as a potential candidate drug to improve the neuropsychiatric behaviors in AD via modulating the expression of the proteins (i.e. GSTP1 and CPLX1) involved in anxiety and depression behaviors. © 2017 BioFactors, 43(4):593-611, 2017.

Adolescent cocaine exposure enhances goal-tracking behavior and impairs hippocampal cell genesis selectively in adult bred low-responder rats

RATIONALE

Environmental challenges during adolescence, such as drug exposure, can cause enduring behavioral and molecular changes that contribute to life-long maladaptive behaviors, including addiction. Selectively bred high-responder (bHR) and low-responder (bLR) rats represent a unique model for assessing the long-term impact of adolescent environmental manipulations, as they inherently differ on a number of addiction-related traits. bHR rats are considered "addiction-prone," whereas bLR rats are "addiction-resilient," at least under baseline conditions. Moreover, relative to bLRs, bHR rats are more likely to attribute incentive motivational value to reward cues, or to "sign-track."

OBJECTIVES

We utilized bHR and bLR rats to determine whether adolescent cocaine exposure can alter their inborn behavioral and neurobiological profiles, with a specific focus on Pavlovian conditioned approach behavior (i.e., sign- vs. goal-tracking) and hippocampal neurogenesis.

METHODS

bHR and bLR rats were administered cocaine (15 mg/kg) or saline for 7 days during adolescence (postnatal day, PND 33-39) and subsequently tested for Pavlovian conditioned approach behavior in adulthood (PND 62-75), wherein an illuminated lever (conditioned stimulus) was followed by the response-independent delivery of a food pellet (unconditioned stimulus). Behaviors directed toward the lever and the food cup were recorded as sign- and goal-tracking, respectively. Hippocampal cell genesis was evaluated on PND 77 by immunohistochemistry.

RESULTS

Adolescent cocaine exposure impaired hippocampal cell genesis (proliferation and survival) and enhanced the inherent propensity to goal-track in adult bLR, but not bHR, rats.

CONCLUSIONS

Adolescent cocaine exposure elicits long-lasting changes in stimulus-reward learning and enduring deficits in hippocampal neurogenesis selectively in adult bLR rats.

Long-lasting memory deficits in mice withdrawn from cocaine are concomitant with neuroadaptations in hippocampal basal activity, GABAergic interneurons and adult neurogenesis

Cocaine addiction disorder is notably aggravated by concomitant cognitive and emotional pathology that impedes recovery. We studied whether a persistent cognitive/emotional dysregulation in mice withdrawn from cocaine holds a neurobiological correlate within the hippocampus, a limbic region with a key role in anxiety and memory but that has been scarcely investigated in cocaine addiction research. Mice were submitted to a chronic cocaine (20 mg/kg/day for 12 days) or vehicle treatment followed by 44 drug-free days. Some mice were then assessed on a battery of emotional (elevated plus-maze, light/dark box, open field, forced swimming) and cognitive (object and place recognition memory, cocaine-induced conditioned place preference, continuous spontaneous alternation) behavioral tests, while other mice remained in their home cage. Relevant hippocampal features [basal c-Fos activity, GABA⁺, parvalbumin (PV)⁺ and neuropeptide Y (NPY)⁺ interneurons and adult neurogenesis (cell proliferation and immature neurons)] were immunohistochemically assessed 73 days after the chronic cocaine or vehicle protocol. The cocaine-withdrawn mice showed no remarkable exploratory or emotional alterations but were consistently impaired in all the cognitive tasks. All the cocaine-withdrawn groups, independent of whether they were submitted to behavioral assessment or not, showed enhanced basal c-Fos expression and an increased number of GABA⁺ cells in the dentate gyrus. Moreover, the cocaine-withdrawn mice previously submitted to behavioral training displayed a blunted experience-dependent regulation of PV⁺ and NPY⁺ neurons in the dentate gyrus, and neurogenesis in the hippocampus. Results highlight the importance of hippocampal neuroplasticity for the ingrained cognitive deficits present during chronic cocaine withdrawal.