Effects of alcohol on brain-derived neurotrophic factor mRNA expression in discrete regions of the rat hippocampus and hypothalamus

Effect of alcohol on Brain-Derived Neurotrophic Factor (BDNF) blood levels: a systematic review and meta-analysis

Brain-Derived Neurotrophic Factor (BDNF) is a vital protein involved in neuronal development, survival, and plasticity. Alcohol consumption has been implicated in various neurocognitive deficits and neurodegenerative disorders. However, the impact of alcohol on BDNF blood levels remains unclear. This systematic review and meta-analysis aimed to investigate the effect of alcohol consumption on BDNF blood levels. A comprehensive search of electronic databases was conducted to identify relevant studies. Eligible studies were selected based on predefined inclusion criteria. Data extraction was performed, and methodological quality was assessed using appropriate tools. A meta-analysis was conducted to estimate the overall effect size of alcohol consumption on BDNF levels. A total of 25 studies met the inclusion criteria and were included in the final analysis. Alcohol use and BDNF blood levels were significantly correlated, according to the meta-analysis (p = 0.008). Overall, it was discovered that drinking alcohol significantly decreased BDNF levels (SMD: - 0.39; 95% CI: - 0.68 to - 0.10; I2: 93%). There was a non-significant trend suggesting that alcohol withdrawal might increase BDNF levels, with an SMD of 0.26 (95% CI: - 0.09 to 0.62; I2: 86%; p = 0.14). Subgroup analysis based on the source of BDNF demonstrated significant differences between the subgroups (p = 0.0008). No significant publication bias was observed. This study showed that alcohol consumption is associated with a significant decrease in BDNF blood levels. The findings suggest a negative impact of alcohol on BDNF levels regardless of alcohol dosage. Further studies are needed to strengthen the evidence and elucidate the underlying mechanisms.

The Role of the Adenosine System on Emotional and Cognitive Disturbances Induced by Ethanol Binge Drinking in the Immature Brain and the Beneficial Effects of Caffeine

Binge drinking intake is the most common pattern of ethanol consumption by adolescents, which elicits emotional disturbances, mainly anxiety and depressive symptoms, as well as cognitive alterations. Ethanol exposure may act on the adenosine neuromodulation system by increasing adenosine levels, consequently increasing the activation of adenosine receptors in the brain. The adenosine modulation system is involved in the control of mood and memory behavior. However, there is a gap in the knowledge about the exact mechanisms related to ethanol exposure’s hazardous effects on the immature brain (i.e., during adolescence) and the role of the adenosine system thereupon. The present review attempts to provide a comprehensive picture of the role of the adenosinergic system on emotional and cognitive disturbances induced by ethanol during adolescence, exploring the potential benefits of caffeine administration in view of its action as a non-selective antagonist of adenosine receptors.

Aerobic exercise as a promising nonpharmacological therapy for the treatment of substance use disorders

Despite the prevalence and public health impact of substance use disorders (SUDs), effective long-term treatments remain elusive. Aerobic exercise is a promising, nonpharmacological treatment currently under investigation as a strategy for preventing drug relapse. Aerobic exercise could be incorporated into the comprehensive treatment regimens for people with substance abuse disorders. Preclinical studies of SUD with animal models have shown that aerobic exercise diminishes drug-seeking behavior, which leads to relapse, in both male and female rats. Nevertheless, little is known regarding the effects of substance abuse-induced cellular and physiological adaptations believed to be responsible for drug-seeking behavior. Accordingly, the overall goal of this review is to provide a summary and an assessment of findings to date, highlighting evidence of the molecular and neurological effects of exercise on adaptations associated with SUD.

Effect of Water and Ethanol Extracts from Hericium erinaceus Solid-State Fermented Wheat Product on the Protection and Repair of Brain Cells in Zebrafish Embryos

Extracts from Hericium erinaceus can cause neural cells to produce nerve growth factor (NGF) and protect against neuron death. The objective of this study was to evaluate the effects of ethanol and hot water extracts from H. erinaceus solid-state fermented wheat product on the brain cells of zebrafish embryos in both pre-dosing protection mode and post-dosing repair mode. The results showed that 1% ethanol could effectively promote zebrafish embryo brain cell death. Both 200 ppm of ethanol and water extracts from H. erinaceus solid-state fermented wheat product protected brain cells and significantly reduced the death of brain cells caused by 1% ethanol treatment in zebrafish. Moreover, the zebrafish embryos were immersed in 1% ethanol for 4 h to cause brain cell damage and were then transferred and soaked in the 200 ppm of ethanol and water extracts from H. erinaceus solid-state fermented wheat product to restore the brain cells damaged by the 1% ethanol. However, the 200 ppm extracts from the unfermented wheat medium had no protective and repairing effects. Moreover, 200 ppm of ethanol and water extracts from H. erinaceus fruiting body had less significant protective and restorative effects on the brain cells of zebrafish embryos. Both the ethanol and hot water extracts from H. erinaceus solid-state fermented wheat product could protect and repair the brain cells of zebrafish embryos damaged by 1% ethanol. Therefore, it has great potential as a raw material for neuroprotective health product.

An in vivo explorative study to observe the protective effects of Puerariae flos extract on chronic ethanol exposure and withdrawal male mice

Protective effects of Puerariae flos extract (PFE) on ethanol (EtOH) exposure have been previously verified. This study attempts to explore the protective effects of PEF on EtOH withdrawal models. Sixty male Kunming mice were involved which were randomly divided into five groups (intact control, EtOH group (35-day EtOH exposure), EtOH withdrawal group (28-day exposure + 7-day withdrawal), EtOH withdrawal group + positive control (Deanxit) group, and EtOH withdrawal group + PFE group). The changes of neuropsychological behaviors; hippocampal BDNF expression and CA1 neuronal density; and plasma corticotropin-releasing hormone (CRH), ACTH, and CORT levels were observed. It was found that depression-like behaviors reduced by EtOH exposure and increased by withdrawal under the 28-day EtOH exposure and 7-day withdrawal conditions. In addition, anxiety-like behaviors worsened by EtOH exposure and unchanged by withdrawal. Deanxit and PEF ameliorated such behaviors (vs. withdrawal group). Hippocampal BDNF expression was significantly downregulated by EtOH exposure and upregulated by withdrawal. Deanxit and PEF significantly upregulated the BDNF expression. The hippocampal CA1 neuronal density significantly decreased by EtOH exposure but unchanged by withdrawal and treatments. The plasma CRH, ACTH, and CORT levels show a significant enhancement by EtOH exposure and reduced by withdrawal. They were further reduced by Deanxit and PEF. The protective effects of PEF on EtOH chronic withdrawal mouse models were verified. The results of this study also indicated a complicated scenario of neuropsychological behaviors, hippocampal BDNF expression, and hypothalamic-pituitary-adrenal axis which are affected by the timing of EtOH exposure and withdrawal.

Tumour Necrosis Factor in Neuroplasticity, Neurogenesis and Alcohol Use Disorder

Alcohol use disorder is a pervasive and detrimental condition that involves changes in neuroplasticity and neurogenesis. Alcohol activates the neuroimmune system and alters the inflammatory status of the brain. Tumour necrosis factor (TNF) is a well characterised neuroimmune signal but its involvement in alcohol use disorder is unknown. In this review, we discuss the variable findings of TNF's effect on neuroplasticity and neurogenesis. Acute ethanol exposure reduces TNF release while chronic alcohol intake generally increases TNF levels. Evidence suggests TNF potentiates excitatory transmission, promotes anxiety during alcohol withdrawal and is involved in drug use in rodents. An association between craving for alcohol and TNF is apparent during withdrawal in humans. While anti-inflammatory therapies show efficacy in reversing neurogenic deficit after alcohol exposure, there is no evidence for TNF's essential involvement in alcohol's effect on neurogenesis. Overall, defining TNF's role in alcohol use disorder is complicated by poor understanding of its variable effects on synaptic transmission and neurogenesis. While TNF may be of relevance during withdrawal, the neuroimmune system likely acts through a larger group of inflammatory cytokines to alter neuroplasticity and neurogenesis. Understanding the individual relevance of TNF in alcohol use disorder awaits a more comprehensive understanding of TNF's effects within the brain.

Growth Factors and Alcohol Use Disorder

Neurotrophic growth factors were originally characterized for their support in neuronal differentiation, outgrowth, and survival during development. However, it has been acknowledged that they also play a vital role in the adult brain. Abnormalities in growth factors have been implicated in a variety of neurological and psychiatric disorders, including alcohol use disorder (AUD). This work focuses on the interaction between alcohol and growth factors. We review literature suggesting that several growth factors play a unique role in the regulation of alcohol consumption, and that breakdown in these growth factor systems is linked to the development of AUD. Specifically, we focus on the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), fibroblast growth factor 2 (FGF2), and insulin growth factor 1 (IGF-1). We also review the literature on the potential role of midkine (MDK) and pleiotrophin (PTN) and their receptor, anaplastic lymphoma kinase (ALK), in AUD. We show that alcohol alters the expression of these growth factors or their receptors in brain regions previously implicated in addiction, and that manipulations on these growth factors and their downstream signaling can affect alcohol-drinking behaviors in animal models. We conclude that there is a need for translational and clinical research to assess the therapeutic potential of new pharmacotherapies targeting these systems.

Alcohol as an early life stressor: Epigenetics, metabolic, neuroendocrine and neurobehavioral implications

Ethanol exposure during gestation is an early life stressor that profoundly dysregulates structure and functions of the embryonal nervous system, altering the cognitive and behavioral development. Such dysregulation is also achieved by epigenetic mechanisms, which, altering the chromatin structure, redraw the entire pattern of gene expression. In parallel, an oxidative stress response at the cellular level and a global upregulation of neuroendocrine stress response, regulated by the HPA axis, exist and persist in adulthood. This neurobehavioral framework matches those observed in other psychiatric diseases such as mood diseases, depression, autism; those early life stressing events, although probably triggered by specific and different epigenetic mechanisms, give rise to largely overlapping neurobehavioral phenotypes. An early diagnosis of prenatal alcohol exposure, using reliable markers of ethanol intake, together with a deeper understanding of the pathogenic mechanisms, some of them reversible by their nature, can offer a temporal "window" of intervention. Supplementing a mother's diet with protective and antioxidant substances in addition to supportive psychological therapies can protect newborns from being affected.

On the interaction between BDNF and serotonin systems: The effects of long-term ethanol consumption in mice

We investigated the effect of chronic (6 weeks) consumption of 10% alcohol on the principal elements of BDNF (BDNF, proBDNF, p75, and TrkB receptors) and 5-HT (5-HT, 5-HIAA, tryptophan hydroxylase-2 [Tph-2], 5-HT transporter [5-HTT], 5-HT_1A, 5-HT_2A, and 5-HT₇ receptors) systems in the brain of C57Bl/6 mice. BDNF mRNA level in the raphe nuclei area and BDNF protein level in the hippocampus were lowered in ethanol-treated mice. The increase in proBDNF protein level in the raphe nuclei area, cortex, and amygdala and the increase of p75 receptor protein levels in the raphe nuclei area were revealed after ethanol exposure. Alcohol intake reduced the protein level and increased the activity of Tph-2, the key enzyme for serotonin biosynthesis in the brain, and increased the main 5-HT metabolite 5-HIAA level and 5-HIAA/5-НТ ratio as well as the 5-HT₇ receptor mRNA level in the raphe nuclei area. In the cortex, 5-HT_2A receptor protein level was reduced, and 5-HIAA/5-HT ratio was increased. These data showed considerable impact of alcoholization on the BDNF system, resulting in proBDNF and p75 receptor expression enhancement. Alcohol-induced changes in BDNF and 5-HT systems were revealed in the raphe nuclei area where the majority of the cell bodies of the 5-HT neurons are localized, as well as in the cortex, hippocampus, and amygdala. Our data suggest that the BDNF/5-HT interaction contributes to the mechanism underlying chronic alcohol-induced neurodegenerative disorders.

An Observational Study of Serum Brain Derived Neurotrophic Factor Levels in Patients with Alcohol Dependence during Withdrawal

Brain-Derived Neurotrophic Factor (BDNF) is a neuropeptide that plays an important role in Central Nervous System development, plasticity, learning, and memory. Its role has been explored in alcohol-dependent patients, though the results have been inconclusive. Thus, we aimed to compare serum BDNF levels in alcohol-dependent patients during withdrawal with age and gender matched controls, and assess changes in BDNF levels in the initial abstinence period. BDNF levels of alcohol-dependent patients (n = 25) were compared with controls (n = 25) at baseline. Additionally, BDNF levels were measured in cases on days 5 and 10 of inpatient detoxification. BDNF levels of controls did not differ with cases on day 1, 5, or 10. But BDNF levels increased significantly during alcohol abstinence from baseline to day 10 (Pillai's Trace F = 3.753, p = .039, partial η² = 0.246), which may suggest its protective role. Thus, serum BDNF values may be potentially used as a biomarker to assess the abstinence state. However, longitudinal studies in different body samples is essential to better understand the role of BDNF in alcohol dependence.

Receptor Tyrosine Kinases as Therapeutic Targets for Alcohol Use Disorder

The receptor tyrosine kinases (RTKs) are a large family of proteins that transduce extracellular signals to the inside of the cell to ultimately affect important cellular functions such as cell proliferation, survival, apoptosis, differentiation, and migration. They are expressed in the nervous system and can regulate behavior through modulation of neuronal and glial function. As a result, RTKs are implicated in neurodegenerative and psychiatric disorders such as depression and addiction. Evidence has emerged that 5 RTKs (tropomyosin-related kinase B (TrkB), RET proto-oncogene (RET), anaplastic lymphoma kinase (ALK), fibroblast growth factor receptor (FGFR), and epidermal growth factor receptor (EGFR)) modulate alcohol drinking and other behaviors related to alcohol addiction. RTKs are considered highly "druggable" targets and small-molecule inhibitors of RTKs have been developed for the treatment of various conditions, particularly cancer. These kinases are therefore attractive targets for the development of new pharmacotherapies to treat alcohol use disorder (AUD). This review will examine the preclinical evidence describing TrkB, RET, ALK, FGFR, and EGFR modulation of alcohol drinking and other behaviors relevant to alcohol abuse.

The Long-Term Effects of Ethanol and Corticosterone on the Mood-Related Behaviours and the Balance Between Mature BDNF and proBDNF in Mice

In this study, we aimed to establish the effects of chronic corticosterone (CORT) and ethanol administration on mood-related behaviour and the levels of mature brain-derived neurotrophic factor (mBDNF) and its precursor protein proBDNF in mice. C57BL6 male and female mice received drinking water (n = 22), 1% ethanol in drinking water (n = 16) or 100 μg/ml corticosterone in drinking water (containing 1% ethanol, n = 18) for 4.5 weeks. At the end of experimental protocol, the open field test (OFT) and elevated plus maze test were performed. Brain and adrenal tissues were collected and mBDNF and proBDNF were measured by ELISA assays. We found that the mice fed with corticosterone and ethanol developed anxiety-like behaviours as evidenced by reduced time in the central zone in the OFT compared with the control group. Both proBDNF and mBDNF were significantly decreased in the corticosterone and ethanol groups compared with the control group in the prefrontal cortex, hippocampus, hypothalamus and adrenal. The ratio of proBDNF/mBDNF in prefrontal cortex in the corticosterone group was increased compared with the ethanol group. Our data suggest that the ratio of proBDNF/mBDNF is differentially regulated in different tissues. Ethanol and corticosterone downregulate both mBDNF and proBDNF and alter the balance of proBDNF/mBDNF in some tissues. In conclusion, the ethanol and corticosterone may cause abnormal regulation of mBDNF and proBDNF which may lead to mood disorders.

Subventricular zone neural precursor cell responses after traumatic brain injury and binge alcohol in male rats

Traumatic brain injury (TBI) is a major cause of disability worldwide. Additionally, many TBI patients are intoxicated with alcohol at the time of injury, but the impact of acute intoxication on recovery from brain injury is not well understood. We have previously found that binge alcohol prior to TBI impairs spontaneous functional sensorimotor recovery. However, whether alcohol administration in this setting affects reactive neurogenesis after TBI is not known. This study, therefore, sought to determine the short- and long-term effects of pre-TBI binge alcohol on neural precursor cell responses in the subventricular zone (SVZ) following brain injury in male rats. We found that TBI alone significantly increased proliferation in the SVZ as early as 24 hr after injury. Surprisingly, binge alcohol alone also significantly increased proliferation in the SVZ after 24 hr. However, a combined binge alcohol and TBI regimen resulted in decreased TBI-induced proliferation in the SVZ at 24 hr and 1 week post-TBI. Furthermore, at 6 weeks after TBI, binge alcohol administered at the time of TBI significantly decreased the TBI-induced neuroblast response in the SVZ and the rostral migratory stream (RMS). The results from this study suggest that pre-TBI binge alcohol negatively impacts reparative processes in the brain by decreasing short-term neural precursor cell proliferative responses as well as long-term neuroblasts in the SVZ and RMS.

NGF and BDNF Alterations by Prenatal Alcohol Exposure

BACKGROUND

It is now widely established that the devastating effects of prenatal alcohol exposure on the embryo and fetus development cause marked cognitive and neurobiological deficits in the newborns. The negative effects of the gestational alcohol use have been well documented and known for some time. However, also the subtle role of alcohol consumption by fathers prior to mating is drawing special attention.

OBJECTIVE

Both paternal and maternal alcohol exposure has been shown to affect the neurotrophins' signalling pathways in the brain and in target organs of ethanol intoxication. Neurotrophins, in particular nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), are molecules playing a pivotal role in the survival, development and function of the peripheral and central nervous systems but also in the pathogenesis of developmental defects caused by alcohol exposure.

METHODS

New researches from the available literature and experimental data from our laboratory are presented in this review to offer the most recent findings regarding the effects of maternal and paternal prenatal ethanol exposure especially on the neurotrophins' signalling pathways.

RESULTS

NGF and BDNF changes play a subtle role in short- and long-lasting effects of alcohol in ethanol target tissues, including neuronal cell death and severe cognitive and physiological deficits in the newborns.

CONCLUSION

The review suggests a possible therapeutic intervention based on the use of specific molecules with antioxidant properties in order to induce a potential prevention of the harmful effects of the paternal and/or maternal alcohol exposure.

Voluntary alcohol consumption exacerbated high fat diet-induced cognitive deficits by NF-κB-calpain dependent apoptotic cell death in rat hippocampus: Ameliorative effect of melatonin

Modern sedentary lifestyle with altered dietary habits imposes the risk of human health towards several metabolic disorders such as obesity. The metabolic insults negatively affect the mental health status and quality life of affected individuals. Melatonin is a potent antioxidant with anti-inflammatory and neuroprotective properties. The aim of the present study was to investigate the protective effect of melatonin on the cognitive and neurochemical deficits induced by the high-fat diet (HFD) and alcohol (ALC) alone or in combination (HFD + ALC) in rats. Male Wistar rats were given ALC (3-15% i.e. increased gradually) and HFD for 12 weeks in different experimental groups. After 12 weeks, we found that simultaneous consumption of HFD and ALC exacerbates cognitive dysfunction and neurochemical anomalies. However, melatonin (10 mg/kg/day, i.p.) treatment for four weeks significantly prevented memory deficits, oxidative stress and neuroinflammation in HFD, ALC and HFD + ALC groups. RT-PCR analysis showed down-regulation of nuclear factor erythroid 2-related factor 2 (Nrf-2) and heme oxygenase-1 (HO-1) in ALC and HFD + ALC groups. Moreover, caspase-3 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) mRNA expression level were found up-regulated in hippocampus of HFD, ALC and HFD + ALC groups. However, calpain expression was found up-regulated only in the hippocampus of HFD + ALC group. Chronic treatment with melatonin significantly restored the aberrant gene expression level in HFD, ALC and HFD + ALC group. In conclusion, our findings indicated that melatonin can mitigate the HFD and ALC-induced cognitive deficits via attenuation of oxidative stress and calpain-1 dependent as well as independent caspase-3 mediated neuronal cell death.

Wheel running during chronic nicotine exposure is protective against mecamylamine-precipitated withdrawal and up-regulates hippocampal α7 nACh receptors in mice

BACKGROUND AND PURPOSE

Evidence suggests that exercise decreases nicotine withdrawal symptoms in humans; however, the mechanisms mediating this effect are unclear. We investigated, in a mouse model, the effect of exercise intensity during chronic nicotine exposure on nicotine withdrawal severity, binding of α4β2*, α7 nicotinic acetylcholine (nAChR), μ-opioid (μ receptors) and D2 dopamine receptors and on brain-derived neurotrophic factor (BDNF) and plasma corticosterone levels.

EXPERIMENTAL APPROACH

Male C57Bl/6J mice treated with nicotine (minipump, 24 mg·kg-1 ·day-1 ) or saline for 14 days underwent one of three concurrent exercise regimes: 24, 2 or 0 h·day-1 voluntary wheel running. Mecamylamine-precipitated withdrawal symptoms were assessed on day 14. Quantitative autoradiography of α4β2*, α7 nAChRs, μ receptors and D2 receptor binding was performed in brain sections of these mice. Plasma corticosterone and brain BDNF levels were also measured.

KEY RESULTS

Nicotine-treated mice undertaking 2 or 24 h·day-1 wheel running displayed a significant reduction in withdrawal symptom severity compared with the sedentary group. Wheel running induced a significant up-regulation of α7 nAChR binding in the CA2/3 area of the hippocampus of nicotine-treated mice. Neither exercise nor nicotine treatment affected μ or D2 receptor binding or BDNF levels. Nicotine withdrawal increased plasma corticosterone levels and α4β2* nAChR binding, irrespective of exercise regimen.

CONCLUSIONS AND IMPLICATIONS

We demonstrated for the first time a profound effect of exercise on α7 nAChRs in nicotine-dependent animals, irrespective of exercise intensity. These findings shed light onto the mechanism underlining the protective effect of exercise on the development of nicotine dependence.

LINKED ARTICLES

This article is part of a themed section on Nicotinic Acetylcholine Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.11/issuetoc.

Synaptic Ultrastructure Might Be Involved in HCN1-Related BDNF mRNA in Withdrawal-Anxiety After Ethanol Dependence

Withdrawal from ethanol dependence has been associated with heightened anxiety and reduced expression of Brain-derived neurotropic factor which promotes the synaptic transmission and plasticity of synapses. Hyperpolarization-activated cyclic nucleotide-gated channel 1 regulates expression; however, whether Hyperpolarization-activated cyclic nucleotide-gated channel 1-related Brain-derived neurotropic factor is involved in the synaptic ultrastructure that generates withdrawal-anxiety has been poorly perceived. Sprague-Dawley rats were treated with ethanol 3-9% (v/v) for a period of 21 days. Conditioned place preference and body weight were investigated during ethanol administration. Rats were subjected to behavioral testing and biochemical assessments after ethanol withdrawal, which was induced by abrupt discontinuation of the treatment. The results showed that the ethanol administration induced severe ethanol dependence behaviors, with higher body weight and more time in the ethanol-paired compartment. After withdrawal, rats had a higher total ethanol withdrawal score and explored less. Additionally, increased Hyperpolarization-activated cyclic nucleotide-gated channel 1 protein and gene expression and decreased Brain-derived neurotropic factor protein and gene expression were detected in the Ethanol group. Eventually, there was a negative correlation between the level of Brain-derived neurotropic factor mRNA and Hyperpolarization-activated cyclic nucleotide-gated channel 1 protein. Importantly, the synaptic ultrastructure changed in the Ethanol group, including increased synaptic cleft width and reduction in postsynaptic density thickness or synaptic curvature. The synthesis of the Brain-derived neurotropic factor mRNA could be down-regulated by higher Hyperpolarization-activated cyclic nucleotide-gated channel 1 protein expression. Changes in synaptic ultrastructure may be induced by lower Brain-derived neurotropic factor protein, which could be associated with the withdrawal-anxiety that is experiences after ethanol dependence.

Long-Term Effects of Intermittent Adolescent Alcohol Exposure in Male and Female Rats

Alcohol is a serious public health concern that has a differential impact on individuals depending upon age and sex. Patterns of alcohol consumption have recently changed: heavy episodic drinking—known as binge-drinking—has become most popular among the youth. Herein, we aimed to investigate the consequences of intermittent adolescent alcohol consumption in male and female animals. Thus, Wistar rats were given free access to ethanol (20% in drinking water) or tap water for 2-h sessions during 3 days, and for an additional 4-h session on the 4th day; every week during adolescence, from postnatal day (pnd) 28–52. During this period, animals consumed a moderate amount of alcohol despite blood ethanol concentration (BEC) did not achieve binge-drinking levels. No withdrawal signs were observed: no changes were observed regarding anxiety-like responses in the elevated plus-maze or plasma corticosterone levels (pnd 53–54). In the novel object recognition (NOR) test (pnd 63), a significant deficit in recognition memory was observed in both male and female rats. Western Blot analyses resulted in an increase in the expression of synaptophysin in the frontal cortex (FC) of male and female animals, together with a decrease in the expression of the CB2R in the same brain region. In addition, adolescent alcohol induced, exclusively among females, a decrease in several markers of dopaminergic and serotonergic neurotransmission, in which epigenetic mechanisms, i.e., histone acetylation, might be involved. Taken together, further research is still needed to specifically correlate sex-specific brain and behavioral consequences of adolescent alcohol exposure.

Region-specific expression of precursor and mature brain-derived neurotrophic factors after chronic alcohol exposure

BACKGROUND

Alcohol abuse is a serious health problem worldwide that causes a variety of physical and mental disorders. Research has shown that the brain-derived neurotrophic factor (BDNF) plays an important role in alcohol addiction. The BDNF precursor (proBDNF) exhibits different actions than BDNF through separate receptors and pathways in the central nervous system. However, the effects of proBDNF and BDNF in alcohol addiction are not fully known.

OBJECTIVES

The objective was to identify the expression patterns and effects of proBDNF and BDNF after chronic alcohol exposure.

METHODS

A total of 40 male adult mice were studied. A mouse psychomotor sensitization (PS) model was established to explore the effects of BDNF and proBDNF treatment following chronic alcohol exposure. Reverse transcription PCR (RT-PCR) was performed to measure mRNA levels for BDNF, TrkB, P75NTR, and sortilin in the prefrontal cortex, hippocampus, and dorsal striatum of Kunming mice after chronic alcohol exposure.

RESULTS

In Kunming mice, chronic alcohol exposure up-regulated BDNF and TrkB mRNA levels in the prefrontal cortex, but decreased sortilin and P75 mRNA levels in the dorsal striatum. No changes in mRNA levels were found in other measured brain regions in the alcohol and control groups.

CONCLUSION

Chronic alcohol exposure induced the region-specific expression of BDNF and proBDNF and their respective receptors in the brain. These results suggest that BDNF and proBDNF signaling pathways may play major roles in alcohol preference and addiction.

Lobeline attenuates ethanol abstinence-induced depression-like behavior in mice

Evidence indicates that the brain nicotinic acetylcholine receptor (nAChRs) ligand lobeline reduces depression-like behaviors, ethanol drinking, and nicotine withdrawal-induced depression-like behaviors. The purpose of the present study was to determine the effects of lobeline on ethanol abstinence-induced depression-like behavior and associated neuroadaptive changes in mice. Adult C57BL/6J male mice were allowed to drink 10% ethanol for 4 weeks using a two-bottle choice procedure. Mice were tested after 24 h and 14 days of ethanol abstinence in a forced swim test (FST), a measure for depression-like behavior. Acute lobeline treatment (1 mg/kg) significantly reduced immobility time compared to controls after 24 h and 14 days of abstinence. In addition, abstinence from chronic ethanol exposure reduced serotonin levels in the hippocampus, which was reversed by acute lobeline treatment. Repeated lobeline treatment (1 mg/kg, once daily) for 14 days during ethanol abstinence also significantly reduced FST immobility in mice exposed to ethanol. Chronic ethanol exposure significantly reduced the number of 5-bromo 2'-deoxyuridine (BrdU)-positive cells in the dentate gyrus of the hippocampus, indicating decreased hippocampal cell proliferation. Abstinence from chronic ethanol exposure also decreased brain-derived neurotrophic factor (BDNF) in the dentate gyrus and CA3 region of the hippocampus. In contrast, repeated lobeline treatment significantly increased both BrdU- and BDNF-positive cells. Taken together, our results indicate that lobeline produced antidepressant-like effects, likely by targeting brain β2-containing nAChRs, serotonergic neurotransmission, and/or hippocampal cell proliferation. Therefore, lobeline may have therapeutic utility to treat alcohol abstinence-induced depression.

A role for histone acetylation mechanisms in adolescent alcohol exposure-induced deficits in hippocampal brain-derived neurotrophic factor expression and neurogenesis markers in adulthood

Binge drinking during adolescence is a risk factor for neuropsychiatric disorders that can develop later in life. Histone acetylation is an important epigenetic mechanism that contributes to neurodevelopment. We investigated the effects of adolescent intermittent ethanol (AIE) exposure, as opposed to normal saline (AIS) exposure, on histone acetylation-mediated regulation of brain-derived neurotrophic factor (BDNF) expression and developmental stages of neurogenesis (proliferating and immature neurons) in the hippocampus in adulthood. AIE exposure increased whole hippocampal histone deacetylase (HDAC) activity and decreased binding protein of cyclic adenosine monophosphate response element binding protein (CBP) and histone H3-K9 acetylation levels in the CA1, CA2, and CA3 regions of the hippocampus. BDNF protein and exon IV mRNA levels in the CA1 and CA3 regions of the hippocampus of AIE-exposed adult rats were decreased as compared to AIS-exposed adult rats. AIE-induced anxiety-like behaviors and deficits in histone H3 acetylation at BDNF exon IV promoter in the hippocampus during adulthood, which were reversed by treatment with the HDAC inhibitor, trichostatin A (TSA). Similarly, neurogenesis was inhibited by AIE in adulthood as demonstrated by the decrease in Ki-67 and doublecortin (DCX)-positive cells in the dentate gyrus, which was normalized by TSA treatment. These results indicate that AIE exposure increases HDACs and decreases CBP levels that may be associated with a decrease in histone H3 acetylation in the hippocampus. These epigenetic changes potentially decrease BDNF expression and inhibit neurogenesis in the hippocampus that may be involved in AIE-induced behavioral abnormalities, including anxiety, in adulthood.

Adolescent Alcohol Exposure Persistently Impacts Adult Neurobiology and Behavior

Adolescence is a developmental period when physical and cognitive abilities are optimized, when social skills are consolidated, and when sexuality, adolescent behaviors, and frontal cortical functions mature to adult levels. Adolescents also have unique responses to alcohol compared with adults, being less sensitive to ethanol sedative-motor responses that most likely contribute to binge drinking and blackouts. Population studies find that an early age of drinking onset correlates with increased lifetime risks for the development of alcohol dependence, violence, and injuries. Brain synapses, myelination, and neural circuits mature in adolescence to adult levels in parallel with increased reflection on the consequence of actions and reduced impulsivity and thrill seeking. Alcohol binge drinking could alter human development, but variations in genetics, peer groups, family structure, early life experiences, and the emergence of psychopathology in humans confound studies. As adolescence is common to mammalian species, preclinical models of binge drinking provide insight into the direct impact of alcohol on adolescent development. This review relates human findings to basic science studies, particularly the preclinical studies of the Neurobiology of Adolescent Drinking in Adulthood (NADIA) Consortium. These studies focus on persistent adult changes in neurobiology and behavior following adolescent intermittent ethanol (AIE), a model of underage drinking. NADIA studies and others find that AIE results in the following: increases in adult alcohol drinking, disinhibition, and social anxiety; altered adult synapses, cognition, and sleep; reduced adult neurogenesis, cholinergic, and serotonergic neurons; and increased neuroimmune gene expression and epigenetic modifiers of gene expression. Many of these effects are specific to adolescents and not found in parallel adult studies. AIE can cause a persistence of adolescent-like synaptic physiology, behavior, and sensitivity to alcohol into adulthood. Together, these findings support the hypothesis that adolescent binge drinking leads to long-lasting changes in the adult brain that increase risks of adult psychopathology, particularly for alcohol dependence.

Time-Course Analysis of Brain Regional Expression Network Responses to Chronic Intermittent Ethanol and Withdrawal: Implications for Mechanisms Underlying Excessive Ethanol Consumption

Long lasting abusive consumption, dependence, and withdrawal are characteristic features of alcohol use disorders (AUD). Mechanistically, persistent changes in gene expression are hypothesized to contribute to brain adaptations leading to ethanol toxicity and AUD. We employed repeated chronic intermittent ethanol (CIE) exposure by vapor chamber as a mouse model to simulate the cycles of ethanol exposure and withdrawal commonly seen with AUD. This model has been shown to induce progressive ethanol consumption in rodents. Brain CIE-responsive expression networks were identified by microarray analysis across five regions of the mesolimbic dopamine system and extended amygdala with tissue harvested from 0-hours to 7-days following CIE. Weighted Gene Correlated Network Analysis (WGCNA) was used to identify gene networks over-represented for CIE-induced temporal expression changes across brain regions. Differential gene expression analysis showed that long-lasting gene regulation occurred 7-days after the final cycle of ethanol exposure only in prefrontal cortex (PFC) and hippocampus. Across all brain regions, however, ethanol-responsive expression changes occurred mainly within the first 8-hours after removal from ethanol. Bioinformatics analysis showed that neuroinflammatory responses were seen across multiple brain regions at early time-points, whereas co-expression modules related to neuroplasticity, chromatin remodeling, and neurodevelopment were seen at later time-points and in specific brain regions (PFC or HPC). In PFC a module containing Bdnf was identified as highly CIE responsive in a biphasic manner, with peak changes at 0 hours and 5 days following CIE, suggesting a possible role in mechanisms underlying long-term molecular and behavioral response to CIE. Bioinformatics analysis of this network and several other modules identified Let-7 family microRNAs as potential regulators of gene expression changes induced by CIE. Our results suggest a complex temporal and regional pattern of widespread gene network responses involving neuroinflammatory and neuroplasticity related genes as contributing to physiological and behavioral responses to chronic ethanol.

The Antisense Transcriptome and the Human Brain

The transcriptome of a cell is made up of a varied array of RNA species, including protein-coding RNAs, long non-coding RNAs, short non-coding RNAs, and circular RNAs. The cellular transcriptome is dynamic and can change depending on environmental factors, disease state and cellular context. The human brain has perhaps the most diverse transcriptome profile that is enriched for many species of RNA, including antisense transcripts. Antisense transcripts are produced when both the plus and minus strand of the DNA helix are transcribed at a particular locus. This results in an RNA transcript that has a partial or complete overlap with an intronic or exonic region of the sense transcript. While antisense transcription is known to occur at some level in most organisms, this review focuses specifically on antisense transcription in the brain and how regulation of genes by antisense transcripts can contribute to functional aspects of the healthy and diseased brain. First, we discuss different techniques that can be used in the identification and quantification of antisense transcripts. This is followed by examples of antisense transcription and modes of regulatory function that have been identified in the brain.

Effects of Ethanol on the Expression Level of Various BDNF mRNA Isoforms and Their Encoded Protein in the Hippocampus of Adult and Embryonic Rats

We aimed to compare the effects of oral ethanol (Eth) alone or combined with the phytoestrogen resveratrol (Rsv) on the expression of various brain-derived neurotrophic factor (BDNF) transcripts and the encoded protein pro-BDNF in the hippocampus of pregnant and embryonic rats. A low (0.25 g/kg body weight (BW)/day) dose of Eth produced an increase in the expression of BDNF exons I, III and IV and a decrease in that of the exon IX in embryos, but failed to affect BDNF transcript and pro-BDNF protein expression in adults. However, co-administration of Eth 0.25 g/kg·BW/day and Rsv led to increased expression of BDNF exons I, III and IV and to a small but significant increase in the level of pro-BDNF protein in maternal rats. A high (2.5 g/kg·BW/day) dose of Eth increased the expression of BDNF exons III and IV in embryos, but it decreased the expression of exon IX containing BDNF mRNAs in the maternal rats. While the high dose of Eth alone reduced the level of pro-BDNF in adults, it failed to change the levels of pro-BDNF in embryos. Eth differentially affects the expression pattern of BDNF transcripts and levels of pro-BDNF in the hippocampus of both adult and embryonic rats.

Alcohol dependence-induced regulation of the proliferation and survival of adult brain progenitors is associated with altered BDNF-TrkB signaling

Effects of withdrawal from ethanol drinking in chronic intermittent ethanol vapor (CIE)-exposed dependent rats and air-exposed nondependent rats on proliferation and survival of progenitor cells in the hippocampus and the medial prefrontal cortex (mPFC) were investigated. Rats were injected with 5'-Bromo 2-deoxyuridine 72 h post-CIE to measure proliferation (2 h-old cells) and survival (29-day-old cells) of progenitors born during a time-point previously reported to elicit a proliferative burst in the hippocampus. Hippocampal and mPFC brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B receptor (TrkB) expression were measured 3 h or 21d post-CIE to evaluate neurotrophic signaling during a time point preceding the proliferative burst and survival of newly born progenitors. CIE rats demonstrated elevated drinking compared to nondependent rats and CIE rats maintained elevated drinking following protracted abstinence. Withdrawal from CIE increased BDNF levels in the hippocampus and mPFC, and subsequently increased proliferation in the hippocampus and mPFC compared to nondependent rats and controls. Protracted abstinence from CIE reduced BDNF expression to control levels, and subsequently reduced neurogenesis compared to controls and nondependent rats in the hippocampus. In the mPFC, protracted abstinence reduced BDNF expression to control levels, whereas increased oligodendrogenesis in dependent rats compared to nondependent rats and controls. These results suggest a novel relationship between BDNF and progenitors in the hippocampus and mPFC, in which increased ethanol drinking may alter hippocampal and cortical function in alcohol dependent subjects by altering the cellular composition of newly born progenitors in the hippocampus and mPFC.

Brain-derived neurotrophic factor and addiction: Pathological versus therapeutic effects on drug seeking

Many abused drugs lead to changes in endogenous brain-derived neurotrophic factor (BDNF) expression in neural circuits responsible for addictive behaviors. BDNF is a known molecular mediator of memory consolidation processes, evident at both behavioral and neurophysiological levels. Specific neural circuits are responsible for storing and executing drug-procuring motor programs, whereas other neural circuits are responsible for the active suppression of these "seeking" systems. These seeking-circuits are established as associations are formed between drug-associated cues and the conditioned responses they elicit. Such conditioned responses (e.g. drug seeking) can be diminished either through a passive weakening of seeking- circuits or an active suppression of those circuits through extinction. Extinction learning occurs when the association between cues and drug are violated, for example, by cue exposure without the drug present. Cue exposure therapy has been proposed as a therapeutic avenue for the treatment of addictions. Here we explore the role of BDNF in extinction circuits, compared to seeking-circuits that "incubate" over prolonged withdrawal periods. We begin by discussing the role of BDNF in extinction memory for fear and cocaine-seeking behaviors, where extinction circuits overlap in infralimbic prefrontal cortex (PFC). We highlight the ability of estrogen to promote BDNF-like effects in hippocampal-prefrontal circuits and consider the role of sex differences in extinction and incubation of drug-seeking behaviors. Finally, we examine how opiates and alcohol "break the mold" in terms of BDNF function in extinction circuits.

Alcohol and adult hippocampal neurogenesis: promiscuous drug, wanton effects

Adult neurogenesis is now widely accepted as an important contributor to hippocampal integrity and function but also dysfunction when adult neurogenesis is affected in neuropsychiatric diseases such as alcohol use disorders. Excessive alcohol consumption, the defining characteristic of alcohol use disorders, results in a variety of cognitive and behavioral impairments related wholly or in part to hippocampal structure and function. Recent preclinical work has shown that adult neurogenesis may be one route by which alcohol produces hippocampal neuropathology. Alcohol is a pharmacologically promiscuous drug capable of interfering with adult neurogenesis through multiple mechanisms. This review will discuss the primary mechanisms underlying alcohol-induced changes in adult hippocampal neurogenesis including alcohol's effects on neurotransmitters, CREB and its downstream effectors, and the neurogenic niche.

Innate BDNF expression is associated with ethanol intake in alcohol-preferring AA and alcohol-avoiding ANA rats

We have shown recently that acute administration of ethanol modulates the expression of brain-derived neurotrophic factor (BDNF) in several rat brain areas known to be involved in the development of addiction to ethanol and other drugs of abuse, suggesting that BDNF may be a factor contributing to the neuroadaptive changes set in motion by ethanol exposure. The purpose of the present study was to further clarify the role of BDNF in reinforcement from ethanol and in the development of addiction to ethanol by specifying the effect of acute administration of ethanol (1.5 or 3.0 g/kg i.p.) on the expression profile of BDNF mRNA in the ventral tegmental area and in the terminal areas of the mesolimbic dopamine pathway in the brain of alcohol-preferring AA and alcohol-avoiding ANA rats, selected for high and low voluntary ethanol intake, respectively. The level of BDNF mRNA expression was higher in the amygdala and ventral tegmental area of AA than in those of ANA rats, and there was a trend for a higher level in the nucleus accumbens. In the amygdala and hippocampus, a biphasic change in the BDNF mRNA levels was detected: the levels were decreased at 3 and 6h but increased above the basal levels at 24h. Furthermore, there was a difference between the AA and ANA lines in the effect of ethanol, the ANA rats showing an increase in BDNF mRNA levels while such a change was not seen in AA rats. These findings suggest that the innate levels of BDNF expression may play a role in the mediation of the reinforcing effects of ethanol and in the control of ethanol intake.

Differential cortical neurotrophin and cytogenetic adaptation after voluntary exercise in normal and amnestic rats

Voluntary exercise (VEx) has profound effects on neural and behavioral plasticity, including recovery of CNS trauma and disease. However, the unique regional cortical adaption to VEx has not been elucidated. In a series of experiments, we first examined whether VEx would restore and retain neurotrophin levels in several cortical regions (frontal cortex [FC], retrosplenial cortex [RSC], occipital cortex [OC]) in an animal model (pyrithiamine-induced thiamine deficiency [PTD]) of the amnestic disorder Wernicke-Korsakoff syndrome. In addition, we assessed the time-dependent effect of VEx to rescue performance on a spontaneous alternation task. Following 2-weeks of VEx or stationary housing conditions (Stat), rats were behaviorally tested and brains were harvested either the day after VEx (24-h) or after an additional 2-week period (2-wk). In both control pair-fed (PF) rats and PTD rats, all neurotrophin levels (brain-derived neurotrophic factor [BDNF], nerve growth factor [NGF], and vascular endothelial growth factor) increased at the 24-h period after VEx in the FC and RSC, but not OC. Two-weeks following VEx, BDNF remained elevated in both FC and RSC, whereas NGF remained elevated in only the FC. Interestingly, VEx only recovered cognitive performance in amnestic rats when there was an additional 2-wk adaptation period after VEx. Given this unique temporal profile, Experiment 2 examined the cortical cytogenetic responses in all three cortical regions following a 2-wk adaptation period after VEx. In healthy (PF) rats, VEx increased the survival of progenitor cells in both the FC and RSC, but only increased oligodendrocyte precursor cells (OLPs) in the FC. Furthermore, VEx had a selective effect of only recovering OLPs in the FC in PTD rats. These data reveal the therapeutic potential of exercise to restore cortical plasticity in the amnestic brain, and that the FC is one of the most responsive cortical regions to VEx.

Chronic binge-like alcohol consumption in adolescence causes depression-like symptoms possibly mediated by the effects of BDNF on neurogenesis

Here we investigated whether changes in neurogenesis and brain-derived neurotrophic factor (BDNF) expression are possible mechanisms involved in the depression-like symptom during the withdrawal/abstinence period after chronic binge-pattern alcohol consumption given the limited number of studies addressing the link between these factors in the adolescent brain. Forty-seven male Sprague-Dawley rats were used in the study and the experimental protocol started when rats were 25-days old. Rats were assigned to either: (a) ethanol or (b) control group. Animals in each group were further randomized to receive either: BDNF receptor agonist or vehicle. Rats were trained to self-administer ethanol and the binge protocol consisted of daily 30-min experimental sessions 4h into the dark period for 12days. Two days after the last drinking session, rats were tested in the sucrose preference test to evaluate anhedonia and the open field test after habituation to evaluate behavioral despair. Our data showed that: (1) self-administration of alcohol in a binge-like pattern causes inebriation as defined by the National Institute on Alcohol Abuse and Alcoholism and this pattern of alcohol exposure is associated with the development of a depression-like symptom; (2) no significant difference in blood alcohol levels between the two ethanol groups; and (3) chronic binge drinking resulted in the development of a depressive phenotype, decreased survival and neuronal differentiation of neural progenitor cells in the hippocampus, and decreased BDNF effect during the withdrawal period. But the most important finding in our study is that augmenting BDNF actions through the use of tyrosine kinase B (TrkB, a BDNF receptor) agonist restored neurogenesis and abolished the alcohol-induced anhedonia and despair behaviors seen during the withdrawal/abstinence period. Our results suggest that BDNF might be a molecule that can be targeted for interventions in alcoholism-depression co-incidence.

Deletion of Prkcz increases intermittent ethanol consumption in mice

BACKGROUND

Prkcz has been identified as a gene whose expression is positively correlated with ethanol (EtOH) consumption in mice and is also induced by EtOH. Two proteins are produced from Prkcz: protein kinase M zeta (PKMζ), which is expressed in the nervous system and protein kinase C zeta (PKCζ), which is expressed in other tissues. We examined Prkcz(-/-) mice that lack PKCζ and PKMζ to investigate the role of this gene in behavioral responses to EtOH.

METHODS

Male Prkcz(-/-) and wild-type littermates were tested for EtOH consumption using 4 procedures: 24-hour intermittent access, 4-hour limited intermittent access, 4-day drinking-in-the-dark, and 24-hour continuous access. We also assessed the acute hypnotic effect of EtOH, EtOH reward, and taste preference for sweet-, bitter-, salty-, and umami-flavored solutions. Finally, we determined whether EtOH could increase PKMζ and PKCζ transcripts and protein expression in wild-type mice using quantitative PCR and Western blot analysis.

RESULTS

Prkcz(-/-) mice consumed more EtOH than their wild-type littermates in both intermittent access procedures, but not in the drinking-in-the-dark or 24-hour continuous access procedures. EtOH exposure increased Prkcz transcripts in cultured PC12 cells, and intermittent EtOH consumption increased PKMζ protein in the ventral striatum of wild-type mice.

CONCLUSIONS

Absence of PKMζ in the brain is associated with increased EtOH intake during procedures that incorporate intermittent consumption sessions every other day. Our data suggest that EtOH induces PKMζ, which acts in a negative feedback loop to limit binge-like EtOH consumption.

Cyclic adenosine monophosphate and brain-derived neurotrophic factor decreased oxidative stress and apoptosis in developing hypothalamic neuronal cells: role of microglia

BACKGROUND

We have previously shown that ethanol (EtOH) increases cellular apoptosis to developing neurons via the effects on oxidative stress of neurons directly and via increasing production of microglia-derived factors. To study further the mechanism of EtOH action on neuronal apoptosis, we determined the effects of 2 well-known PKA activators, dibutyryl cAMP (dbcAMP) and brain-derived neurotrophic factor (BDNF), on EtOH-activated oxidative stress and apoptotic processes in the hypothalamic neurons in the presence and absence of microglial cells' influence.

METHODS

In enriched neuronal cells from fetal rat hypothalami treated with EtOH or with conditioned medium from EtOH-treated microglia, we measured cellular apoptosis by the free nucleosome assay and the levels of cAMP, BDNF, O²⁻, reactive oxygen species (ROS), nitrite, glutathione (GSH), and catalase following treatment with EtOH or EtOH-treated microglial culture conditioned medium. Additionally, we tested the effectiveness of dbcAMP and BDNF in preventing EtOH or EtOH-treated microglial conditioned medium on cellular apoptosis and oxidative stress in enriched hypothalamic neuronal cell in primary cultures.

RESULTS

Neuronal cell cultures following treatment with EtOH or EtOH-activated microglial conditioned medium showed decreased production levels of cAMP and BDNF. EtOH also increased apoptotic death as well as oxidative status, as demonstrated by higher cellular levels of oxidants but lower levels of antioxidants, in neuronal cells. These effects of EtOH on oxidative stress and cell death were enhanced by the presence of microglia. Treatment with BDNF or dbcAMP decreased EtOH or EtOH-activated microglial conditioned medium-induced changes in the levels of intracellular free radicals, ROS and O²⁻, nitrite, GSH, and catalase.

CONCLUSIONS

These data support the possibility that EtOH by acting directly and via increasing the production of microglial-derived factors reduces cellular levels of cAMP and BDNF to increase cellular oxidative status and apoptosis in hypothalamic neuronal cells in primary cultures.

Susceptibility to ethanol sensitization is differentially associated with changes in pCREB, trkB and BDNF mRNA expression in the mouse brain

Repeated exposure to ethanol in mice induces behavioural sensitization, a progressive increase in locomotor activity that is common to drugs of abuse. Not all mice however show sensitization to ethanol. The goal of the present study was to examine whether variability in the sensitization response to ethanol (EtOH) is differentially associated with regional brain changes in specific molecular markers associated with neuroplasticity, namely BDNF and its receptor trkB, and levels of phosphorylated cyclic AMP-regulated element-binding protein (pCREB), 14 days after withdrawal from chronic, intermittent EtOH exposure. Male DBA/2NCrl mice received 7 biweekly EtOH (2.2g/kg, i.p.) or saline (SAL) injections and were classified as Sensitized or Non-sensitized on the basis of final locomotor activity (LMA) scores. Brains were removed two weeks later for immunohistochemical and in situ hybridization analyses. Compared to SAL-treated and Non-sensitized mice, Sensitized animals showed a higher number of pCREB-immunoreactive cells in the nucleus accumbens shell (+68% and +50%, respectively) and in the bed nucleus of the stria terminalis (+61% and 46%, respectively), whereas SAL and Non-sensitized groups did not differ from each other. A different pattern was seen when BDNF and trkB mRNA levels were analyzed in the same groups. Non-sensitized mice displayed lower BDNF mRNA in several brain areas and significantly lower trkB levels throughout the brain when compared to either the Sensitized or to SAL groups, which did not differ from each other. These results indicate that sensitization to EtOH is differentially associated with increased pCREB levels in specific brain areas. The observed decrease in BDNF and trkB mRNA in the Non-sensitized group suggests the possibility that EtOH may have neurotoxic effects in a subpopulation of mice, which might in turn prevent the development of behavioural sensitization. The lack of a difference in BDNF and trkB mRNA expression between Sensitized and SAL mice suggests that EtOH sensitization may be mediated by mechanisms different from those mediating sensitization to other psychostimulants.

Brain-derived neurotrophic factor-estrogen interactions in the hippocampal mossy fiber pathway: implications for normal brain function and disease

The neurotrophin brain-derived neurotrophic factor (BDNF) and the steroid hormone estrogen exhibit potent effects on hippocampal neurons during development and in adulthood. BDNF and estrogen have also been implicated in the etiology of diverse types of neurological disorders or psychiatric illnesses, or have been discussed as potentially important in treatment. Although both are typically studied independently, it has been suggested that BDNF mediates several of the effects of estrogen in the hippocampus, and that these interactions play a role in the normal brain as well as disease. Here we focus on the mossy fiber (MF) pathway of the hippocampus, a critical pathway in normal hippocampal function, and a prime example of a location where numerous studies support an interaction between BDNF and estrogen in the rodent brain. We first review the temporal and spatially regulated expression of BDNF and estrogen in the MFs, as well as their receptors. Then we consider the results of studies that suggest that 17β-estradiol alters hippocampal function by its influence on BDNF expression in the MF pathway. We also address the hypothesis that estrogen influences the hippocampus by mechanisms related not only to the mature form of BDNF, acting at trkB receptors, but also by regulating the precursor, proBDNF, acting at p75NTR. We suggest that the interactions between BDNF and 17β-estradiol in the MFs are potentially important in the normal function of the hippocampus, and have implications for sex differences in functions that depend on the MFs and in diseases where MF plasticity has been suggested to play an important role, Alzheimer's disease, epilepsy and addiction.

Serum and plasma brain-derived neurotrophic factor (BDNF) in abstinent alcoholics and social drinkers

Although the effects of alcohol on brain-derived neurotrophic factor (BDNF) have been extensively studied in rodents, BDNF levels have rarely been measured in abstinent, alcohol-dependent (AD) individuals. Interpretation of reported group comparisons of serum BDNF levels is difficult due to limited information regarding analytical variance, biological variability, and the relative contribution of platelet and plasma pools to serum BDNF. Analytical variance (intra- and inter-assay coefficients of variation) of the enzyme-linked immunosorbent assay (ELISA) was characterized. Within- and between-subject variability, and group differences in serum and plasma BDNF, was assessed on three separate days in 16, 4-week abstinent AD individuals (7M/9F) and 16 social drinkers (SDs; 8M/8F). Significantly higher mean (±sd) serum BDNF levels were observed for the AD group compared to the SD (p = 0.003). No significant difference in mean baseline plasma BDNF levels was observed between AD and SD groups. The low analytical variance, high day-to-day within-individual stability and the high degree of individuality demonstrates the potential clinical utility of measuring serum BDNF levels. The low correlations that we observed between plasma and serum levels are congruent with their representing separate pools of BDNF. The observation of higher basal serum BDNF in the AD group without a concomitant elevation in plasma BDNF levels indicates that the elevated serum BDNF in AD patients is not due to greater BDNF exposure. Further research is warranted to fully elucidate mechanisms underlying this alteration and determine the utility of serum BDNF as a predictor or surrogate marker of chronic alcohol abuse.

Brain-derived neurotrophic factor expression after acute administration of ethanol

Earlier findings suggest that, in addition to its well-known neurotrophic role, brain-derived neurotrophic factor (BDNF) is also involved in the rewarding and reinforcing effects of drugs of abuse. The purpose of the present study was to examine the effects of acute administration of ethanol (1.25 or 2.5 g/kg i.p.) on the expression profile of BDNF in the rat brain by determining the BDNF mRNA expression in the frontal cortex, nucleus accumbens, amygdala, hippocampus, and ventral tegmental area. Ethanol decreased BDNF mRNA levels dose-dependently in the hippocampus, and after the higher ethanol dose in the frontal cortex, nucleus accumbens and amygdala, while increasing them in the ventral tegmental area. Furthermore, BDNF mRNA expression was found to be regulated in a temporally different manner in all investigated brain areas. These data suggest that BDNF is involved in the acute effects of ethanol, but separate brain areas may be differentially engaged in the mediation of these effects.

Serum NPY and BNDF response to a behavioral stressor in alcohol-dependent and healthy control participants

RATIONALE

Neuropeptide Y (NPY) and brain-derived neurotrophic factor (BDNF) have been implicated in both the stress response and alcohol addiction. However, few studies have assessed the NPY and BDNF response to stress in alcohol-dependent participants and the concurrent measure of NPY and BDNF has not been reported in human participants.

OBJECTIVE

The purpose of this study was to concurrently assess serum NPY and BDNF, as well as adrenocorticotropin (ACTH) and cortisol, in control and race- and aged-matched abstinent alcohol-dependent participants in response to a stress-inducing public-speaking task.

METHODS

Basal and post-stress serum values of NPY and BDNF, as well as ACTH and cortisol, were assessed in 14 abstinent alcohol-dependent and ten healthy control male participants.

RESULTS

Basal measures were stable over short periods of time and stress induced a significant increase in both NPY (p = 0.002) and BDNF (p = 0.006) as well as ACTH (p < 0.001) and cortisol (p < 0.007). Alcohol-dependent and control groups did not significantly differ on any basal or stress-induced measure. Basal and delta responses of NPY and BDNF were not significantly correlated, and delta peak responses of NPY and BDNF did not correlate with one another or with their respective ACTH and cortisol responses.

CONCLUSIONS

These findings reveal that both serum NPY and BDNF are responsive to behavioral stressors, although their regulatory mechanisms appear to differ from one another and those of the hypothalamic-pituitary-adrenal axis. Differences in basal and stress-induced responses of NPY and BDNF were not supported between control and abstinent alcohol-dependent subjects.

Alcohol-related amnesia and dementia: animal models have revealed the contributions of different etiological factors on neuropathology, neurochemical dysfunction and cognitive impairment

Chronic alcoholism is associated with impaired cognitive functioning. Over 75% of autopsied chronic alcoholics have significant brain damage and over 50% of detoxified alcoholics display some degree of learning and memory impairment. However, the relative contributions of different etiological factors to the development of alcohol-related neuropathology and cognitive impairment are questioned. One reason for this quandary is that both alcohol toxicity and thiamine deficiency result in brain damage and cognitive problems. Two alcohol-related neurological disorders, alcohol-associated dementia and Wernicke-Korsakoff syndrome have been modeled in rodents. These pre-clinical models have elucidated the relative contributions of ethanol toxicity and thiamine deficiency to the development of dementia and amnesia. What is observed in these models--from repeated and chronic ethanol exposure to thiamine deficiency--is a progression of both neural and cognitive dysregulation. Repeated binge exposure to ethanol leads to changes in neural plasticity by reducing GABAergic inhibition and facilitating glutamatergic excitation, long-term chronic ethanol exposure results in hippocampal and cortical cell loss as well as reduced hippocampal neurotrophin protein content critical for neural survival, and thiamine deficiency results in gross pathological lesions in the diencephalon, reduced neurotrophic protein levels, and neurotransmitters levels in the hippocampus and cortex. Behaviorally, after recovery from repeated or chronic ethanol exposure there is impairment in working or episodic memory that can recover with prolonged abstinence. In contrast, after thiamine deficiency there is severe and persistent spatial memory impairments and increased perseverative behavior. The interaction between ethanol and thiamine deficiency does not produce more behavioral or neural pathology, with the exception of reduction of white matter, than long-term thiamine deficiency alone.

Alcohol induced depressive-like behavior is associated with a reduction in hippocampal BDNF

Strong positive correlation between depression and alcoholism is evident in epidemiological reports. However, a causal relationship for this co-morbidity has not been established. We have observed that chronic daily exposure to a relatively high dose of alcohol can induce depressive-like behavior in rats and that pretreatment with nomifensine or imipramine can block the "depressogenic" effects of alcohol. Since brain derived neurotrophic factor (BDNF) is considered to play an important role in depressive-like behaviors and its elevation, particularly in the hippocampus, appears to be critical for the action of many antidepressants, we hypothesized that: 1. WKY rats, a putative animal model of depression, will show a lower hippocampal BDNF compared to their control Wistar rats, 2. Alcohol-induced depressive like behavior will be associated with a significant decrease in hippocampal BDNF and 3. Treatments with antidepressants will normalize hippocampal BDNF. These postulates were verified by measuring hippocampal BDNF in Wistar and WKY rats at baseline, following chronic (10 day) treatment with alcohol and combination of alcohol with nomifensine or imipramine. Alcohol was administered via inhalation chamber (3 h/day) such that a blood alcohol level of approximately 150 mg% was achieved. Nomifensine (10 mg/kg) or imipramine (10 mg/kg) was administered i.p. daily immediately after alcohol exposure. BDNF was measured by standard ELISA kit. The results support a role for central BDNF in depressogenic effects of alcohol and antidepressant effects of nomifensine and imipramine. Moreover, depression per se as manifested in WKY rats may be associated with a reduction in hippocampal BDNF.

Effect of oral resveratrol on the BDNF gene expression in the hippocampus of the rat brain

Resveratrol is a plant polyphenolic compound. Evidence indicates that resveratrol has beneficial effects against aging and neurodegenerative diseases. The goal of our study was in vivo examination of the effects of resveratrol on the abundance of mRNA encoding Brain Derived Neurotrophic Factor (BDNF) in the hippocampus of rat brain. Rats were administrated orally by different doses (2.5-20 mg/kg bwt) of resveratrol for 3, 10 and 30 days. Saline was used as control and 10% ethanol in saline was used as vehicle for resveratrol. Measurement of BDNF mRNA by Real-time RT-PCR showed that levels of the mRNA for BDNF were significantly and dose dependently elevated in the hippocampal tissues of rats. The findings suggest that the neuroprotective effects of resveratrol may be at least partly due to its inducing effects on the expression levels of the BDNF mRNA.

Differential patterns of serum brain-derived neurotrophic factor levels in alcoholic patients with and without delirium tremens during acute withdrawal

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is associated with alcohol addiction and withdrawal-related neurotoxicity. Delirium tremens (DT) is the most serious complication of alcohol withdrawal syndrome (AWS). In this study, we explored the differences in serum BDNF levels, measured at baseline and 1 week after alcohol withdrawal among alcoholic patients with and without DT.

METHODS

Sixty-five inpatients, fulfilling the DSM-IV criteria of alcohol dependence and admitted for alcohol detoxification, as well as 39 healthy control subjects were enrolled. The alcoholic patients were divided by the appearance of DTs into the DT group (n = 25) and non-DT group (n = 40). We collected blood samples of the patient groups on the first and seventh days of alcohol withdrawal and measured serum BDNF levels by sandwich enzyme-linked immunosorbent assay.

RESULTS

Serum BDNF levels differed significantly among the three groups: (i) control group 14.8 ± 4.7 ng/ml; (ii) non-DT group 12.3 ± 3.3 ng/ml; (iii) DT group 6.2 ± 2.6 ng/ml (p < 0.001). One week after alcohol withdrawal, the BDNF levels increased significantly for both alcoholic groups. While non-DT group had comparable BDNF levels (13.4 ± 3.5 ng/ml) with controls, the DT group still exhibited lower levels (8.9 ± 4.4 ng/ml).

CONCLUSIONS

This study suggests chronic drinking leads to a reduction in BDNF levels, and patients with more deficient BDNF expression are vulnerable to the development of DTs. Additionally, BDNF levels elevated after prompt alcohol detoxification treatment. These findings indicate that BDNF could involve modifying the phenotypes of AWS as well as the pertinent neuroadaptive processes of alcohol dependence.

Molecular and genetic substrates linking stress and addiction

Drug addiction is one of the top three health concerns in the United States in terms of economic and health care costs. Despite this, there are very few effective treatment options available. Therefore, understanding the causes and molecular mechanisms underlying the transition from casual drug use to compulsive drug addiction could aid in the development of treatment options. Studies in humans and animal models indicate that stress can lead to both vulnerability to develop addiction, and increased drug taking and relapse in addicted individuals. Exposure to stress or drugs of abuse results in long-term adaptations in the brain that are likely to involve persistent alterations in gene expression or activation of transcription factors, such as the cAMP Response Element Binding (CREB) protein. The signaling pathways controlled by CREB have been strongly implicated in drug addiction and stress. Many potential CREB target genes have been identified based on the presence of a CRE element in promoter DNA sequences. These include, but are not limited to CRF, BDNF, and dynorphin. These genes have been associated with initiation or reinstatement of drug reward and are altered in one direction or the other following stress. While many reviews have examined the interactions between stress and addiction, the goal of this review was to focus on specific molecules that play key roles in both stress and addiction and are therefore posed to mediate the interaction between the two. Focus on these molecules could provide us with new targets for pharmacological treatments for addiction.

The role of GABA(A) receptors in the acute and chronic effects of ethanol: a decade of progress

The past decade has brought many advances in our understanding of GABA(A) receptor-mediated ethanol action in the central nervous system. We now know that specific GABA(A) receptor subtypes are sensitive to ethanol at doses attained during social drinking while other subtypes respond to ethanol at doses attained by severe intoxication. Furthermore, ethanol increases GABAergic neurotransmission through indirect effects, including the elevation of endogenous GABAergic neuroactive steroids, presynaptic release of GABA, and dephosphorylation of GABA(A) receptors promoting increases in GABA sensitivity. Ethanol's effects on intracellular signaling also influence GABAergic transmission in multiple ways that vary across brain regions and cell types. The effects of chronic ethanol administration are influenced by adaptations in GABA(A) receptor function, expression, trafficking, and subcellular localization that contribute to ethanol tolerance, dependence, and withdrawal hyperexcitability. Adolescents exhibit altered sensitivity to ethanol actions, the tendency for higher drinking and longer lasting GABAergic adaptations to chronic ethanol administration. The elucidation of the mechanisms that underlie adaptations to ethanol exposure are leading to a better understanding of the regulation of inhibitory transmission and new targets for therapies to support recovery from ethanol withdrawal and alcoholism.