Effects of chronic alcohol consumption on spatial reference and working memory tasks

Ketamine alleviates fear memory and spatial cognition deficits in a PTSD rat model via the BDNF signaling pathway of the hippocampus and amygdala

BACKGROUND

Post-traumatic stress disorder (PTSD) is associated with traumatic stress experiences. This condition can be accompanied by learning and cognitive deficits. Studies have demonstrated that ketamine can rapidly and significantly alleviate symptoms in patients with chronic PTSD. Nonetheless, the effects of ketamine on neurocognitive impairment and its mechanism of action in PTSD remain unclear.

METHODS

In this study, different concentrations of ketamine (5, 10, 15, and 20 mg/kg, i.p.) were evaluated in rat models of single prolonged stress and electrophonic shock (SPS&S). Expression levels of brain-derived neurotrophic factor (BDNF) and post-synaptic density-95 (PSD-95) in the hippocampus (HIP) and amygdala (AMG) were determined by Western blot analysis and immunohistochemistry.

RESULTS

The data showed that rats subjected to SPS&S exhibited significant PTSD-like cognitive impairment. The effect of ketamine on SPS&S-induced neurocognitive function showed a U-shaped dose effect in rats. A single administration of ketamine at a dosage of 10-15 mg/kg resulted in significant changes in behavioral outcomes. These manifestations of improvement in cognitive function and molecular changes were reversed at high doses (15-20 mg/kg).

CONCLUSION

Overall, ketamine reversed SPS&S-induced fear and spatial memory impairment and the down-regulation of BDNF and BDNF-related PSD-95 signaling in the HIP and AMG. A dose equal to 15 mg/kg rapidly reversed the behavioral and molecular changes and promoted the amelioration of cognitive dysfunction. The enhanced association of BDNF signaling with PSD-95 effects could be involved in the therapeutic efficiency of ketamine for PTSD.

Chronic Intermittent Ethanol Administration during Adolescence Produces Sex Dependent Impairments in Behavioral Flexibility and Survivability

Chronic intermittent ethanol exposure during adolescence produces behavioral impairments and neurobiological changes that can last into young adulthood. One such behavioral impairment is reduced behavioral flexibility, a behavioral impairment that has been correlated with the risk for increased ethanol intake. In the current study, we investigated if chronic intermittent ethanol exposure during adolescence alters cognition, including behavioral flexibility, over a 22-month testing period. Female and male rats were treated with either 3.0 g/kg or 5.0 g/kg ethanol via gavage in a chronic intermittent fashion during adolescence and then tested every 4 to 5 months on a series of cognitive measures in the Morris water maze. Chronic intermittent ethanol selectively impaired behavioral flexibility in both female and male rats, although the pattern of results was different as a function of sex. In addition, female, but not male, rats were impaired in a short-term relearning test. Finally, male rats administered ethanol during adolescence were significantly more likely to not survive the 22-month experiment compared to female rats administered ethanol during adolescence. The current results demonstrate that adolescence is a unique period of development where chronic intermittent ethanol exposure produces long-lasting, selective cognitive impairments across the lifespan.

Therapeutic Interventions of Gut-Brain Axis as Novel Strategies for Treatment of Alcohol Use Disorder Associated Cognitive and Mood Dysfunction

Alcohol use disorders (AUD) is characterized by persistent or intermittent alcohol cravings and compulsive drinking. The functional changes in the central nervous system (CNS) after alcohol consumption are alcohol-associated cognitive impairment and mood disorders, which are major health issues reported in AUDs. Studies have shown that transferring the intestinal microbiota from AUDs patients to germ-free animals causes learning and memory dysfunction, depression and anxiety-like behavior, indicating the vital role of intestinal microbiota in development of neuropsychiatric disorders in AUD. Intestinal flora composition of AUD patients are significantly different from normal people, suggesting that intestinal flora imbalance orchestrate the development of neuropsychiatric disorders in AUD. Studies suggests that gut microbiome links bidirectional signaling network of the enteric nervous system (ENS) to central nervous system (CNS), forming gut-microbe-brain axis (brain-gut axis). In this review, we discussed pathogenesis and possible treatment of AUD-induced cognitive deficits, anxiety, and depression disorders. Further, we described the mechanism of intestinal flora imbalance and dysfunction of hippocampus-amygdala-frontal cortex (gut-limbic circuit system dysfunction). Therefore, we postulate therapeutic interventions of gut-brain axis as novel strategies for treatment of AUD-induced neuropsychiatric disorders.

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.

Long-Lasting Sex-Specific Effects Based On Emotion- and Cognition-Related Behavioral Assessment of Adult Rats After Post-Traumatic Stress Disorder From Different Lengths of Maternal Separation

Adverse early life stress is a major cause of vulnerability to various mental disorders in adulthood, including post-traumatic stress disorder (PTSD). Recent studies have suggested that early life stress can help the body adapt optimally when faced with stressful trauma in adult life. An interaction may exist between early life stress (e.g., childhood trauma) and vulnerability to PTSD. This study aimed to evaluate emotion-related behaviors and verify the long-lasting effects of cognitive aspects of PTSD after exposure to severe adverse early life stress, such as long-term separation. Adverse early life stress was simulated by subjecting rats to 3 or 6 consecutive hours of maternal separation (MS) daily, from postnatal day (PND) 2 to PND 14. Single-prolonged stress (SPS) was simulated on PND 80 to imitate other adulthood stresses of PTSD with gender divisions (M-MS3h-PTSD, F-MS3h-PTSD, M-MS6h-PTSD, F-MS6h-PTSD, M-PTSD, and F-PTSD). After the MS and PTSD sessions, behavioral tests were conducted to assess the effectiveness of these treatments, which included an open field test (OFT), elevated plus maze test (EPMT), water maze test (WMT), and forced swimming test (FST) to detect anxiety-like behavior (OFT and EPMT), memory behavior (WMT), and depressive behavior (FST). The M-MS3h-PTSD group had fewer time entries into the open arms of EPMT than the F-MS3h-PTSD group, and the M-MS6h-PTSD group demonstrated fewer up-right postures in the OFT than the F-MS6h-PTSD group. The M-MS3h-PTSD group exhibited more exploratory behavior than the M-MS6h-PTSD and M-PTSD groups in the OFT. Less exploratory behavior was observed in the F-MS3h-PTSD group than in the F-MS6h-PTSD group, which demonstrated significantly increased freezing times in the FST compared to the F-PTSD group. The WMT revealed significant differences in learning and memory performance between the M-MS3h-PTSD group and other treatment groups, which were not found in the female rats. These findings demonstrate that an early stressful experience, such as MS, may be involved in helping the body adapt optimally when faced with additional trauma in adulthood, although mild early life stress might benefit learning and memory among males.

Jacobian Maps Reveal Under-reported Brain Regions Sensitive to Extreme Binge Ethanol Intoxication in the Rat

Individuals aged 12-20 years drink 11% of all alcohol consumed in the United States with more than 90% consumed in the form of binge drinking. Early onset alcohol use is a strong predictor of future alcohol dependence. The study of the effects of excessive alcohol use on the human brain is hampered by limited information regarding the quantity and frequency of exposure to alcohol. Animal models can control for age at alcohol exposure onset and enable isolation of neural substrates of exposure to different patterns and quantities of ethanol (EtOH). As with humans, a frequently used binge exposure model is thought to produce dependence and affect predominantly corticolimbic brain regions. in vivo neuroimaging enables animals models to be examined longitudinally, allowing for each animal to serve as its own control. Accordingly, we conducted 3 magnetic resonance imaging (MRI) sessions (baseline, binge, recovery) to track structure throughout the brains of wild type Wistar rats to test the hypothesis that binge EtOH exposure affects specific brain regions in addition to corticolimbic circuitry. Voxel-based comparisons of 13 EtOH- vs. 12 water- exposed animals identified significant thalamic shrinkage and lateral ventricular enlargement as occurring with EtOH exposure, but recovering with a week of abstinence. By contrast, pretectal nuclei and superior and inferior colliculi shrank in response to binge EtOH treatment but did not recover with abstinence. These results identify brainstem structures that have been relatively underreported but are relevant for localizing neurocircuitry relevant to the dynamic course of alcoholism.

Effects of the Positive Allosteric Modulator of Metabotropic Glutamate Receptor 5, VU-29, on Impairment of Novel Object Recognition Induced by Acute Ethanol and Ethanol Withdrawal in Rats

Glutamate is essential for learning and memory processes, and acute and chronic exposures to ethanol (or protracted abstinence) alter glutamatergic transmission. In the current study, we investigated the effects of VU-29, positive allosteric modulator of metabotropic glutamate 5 (mGlu5) receptor, on the acute ethanol- and ethanol withdrawal-induced impairment of novel object recognition (NOR) task in rats. The influence of VU-29 (30 mg/kg) on memory retrieval was measured (a) at 4-h delay after acute ethanol administration, as well as (b) after acute withdrawal (24 and 48 h) of repeated (2.0 g/kg, once daily for 7 days) ethanol administration. Additionally, the effects of VU-29 on expression of mGlu5 and mGlu2 receptor proteins in the hippocampus, prefrontal cortex, and striatum were determined 48 h after ethanol withdrawal. Our results indicated that VU-29, given before acute ethanol administration, prevented the ethanol-induced impairments in spatial memory retrieval. Furthermore, VU-29 given before the testing session on the first day of abstinence facilitated NOR performance in ethanol-withdrawn rats at 4- and 24-h delay after administration. Our ELISA results show that VU-29 normalized ethanol withdrawal induced increase in expression of mGlu5 receptor protein in the hippocampus, prefrontal cortex, and striatum, as well as expression of mGlu2 receptor protein in the hippocampus. Thus, results from our study indicate that positive modulation of mGlu5 receptor prevented and reversed ethanol-induced memory impairment. Moreover, mGlu5 (hippocampus, prefrontal cortex, and striatum) and mGlu2 (hippocampus) receptors play an important role in the ethanol-induced recognition memory impairment induced by ethanol withdrawal.

Spatial navigation deficits in amnestic mild cognitive impairment with neuropsychiatric comorbidity

AIMS

To find out whether neuropsychiatric comorbidity (comMCI) influences spatial navigation performance in amnestic mild cognitive impairment (aMCI).

METHODS

We recruited aMCI patients with (n = 21) and without (n = 21) neuropsychiatric comorbidity or alcohol abuse, matched for global cognitive impairment and cognitively healthy elderly participants (HE, n = 22). They completed the Mini-Mental State Examination and a virtual Hidden Goal Task in egocentric, allocentric, and delayed recall subtests.

RESULTS

In allocentric navigation, aMCI and comMCI performed significantly worse than HE and similarly to each other. Although aMCI performed significantly worse at egocentric navigation than HE, they performed significantly better than patients with comMCI.

CONCLUSIONS

Despite the growing burden of dementia and the prevalence of neuropsychiatric symptoms in the elderly population, comMCI remains under-studied. Since trials often assess "pure" aMCI, we may underestimate patients' navigation and other deficits. This finding emphasizes the importance of taking account of the cognitive effects of psychiatric disorders in aMCI.

Adult Neurogenesis and Psychiatric Disorders

Psychiatric disorders continue to be among the most challenging disorders to diagnose and treat because there is no single genetic or anatomical locus that is causative for the disease. Current treatments are often blunt tools used to ameliorate the most severe symptoms, at the risk of disrupting functional neural systems. There is a critical need to develop new therapeutic strategies that can target circumscribed functional or anatomical domains of pathology. Adult hippocampal neurogenesis may be one such domain. Here, we review the evidence suggesting that adult hippocampal neurogenesis plays a role in emotional regulation and forms of learning and memory that include temporal and spatial memory encoding and context discrimination, and that its dysregulation is associated with psychiatric disorders, such as affective disorders, schizophrenia, and drug addiction. Further, adult neurogenesis has proven to be an effective model to investigate basic processes of neuronal development and converging evidence suggests that aberrant neural development may be an etiological factor, even in late-onset diseases. Constitutive neurogenesis in the hippocampus of the mature brain reflects large-scale plasticity unique to this region and could be a potential hub for modulation of a subset of cognitive and affective behaviors that are affected by multiple psychiatric disorders.

Ethanol Induced Brain Lipid Changes in Mice Assessed by Mass Spectrometry

Alcohol abuse is a chronic disease characterized by the consumption of alcohol at a level that interferes with physical and mental health and causes serious and persistent changes in the brain. Lipid metabolism is of particular interest due to its high concentration in the brain. Lipids are the main component of cell membranes, are involved in cell signaling, signal transduction, and energy storage. In this study, we analyzed lipid composition of chronically ethanol exposed mouse brains. Juvenile (JUV) and adult (ADU) mice were placed on a daily limited-access ethanol intake model for 52 days. After euthanasia, brains were harvested, and total lipids were extracted from brain homogenates. Samples were analyzed using high resolution mass spectrometry and processed by multivariate and univariate statistical analysis. Significant lipid changes were observed in different classes including sphingolipids, fatty acids, lysophosphatidylcholines, and other glycerophospholipids.

Pharmacological activation of CB2 receptors counteracts the deleterious effect of ethanol on cell proliferation in the main neurogenic zones of the adult rat brain

Chronic alcohol exposure reduces endocannabinoid activity and disrupts adult neurogenesis in rodents, which results in structural and functional alterations. Cannabinoid receptor agonists promote adult neural progenitor cell (NPC) proliferation. We evaluated the protective effects of the selective CB₁ receptor agonist ACEA, the selective CB₂ receptor agonist JWH133 and the fatty-acid amide-hydrolase (FAAH) inhibitor URB597, which enhances endocannabinoid receptor activity, on NPC proliferation in rats with forced consumption of ethanol (10%) or sucrose liquid diets for 2 weeks. We performed immunohistochemical and stereological analyses of cells expressing the mitotic phosphorylation of histone-3 (phospho-H3+) and the replicating cell DNA marker 5-bromo-2'-deoxyuridine (BrdU+) in the main neurogenic zones of adult brain: subgranular zone of dentate gyrus (SGZ), subventricular zone of lateral ventricles (SVZ) and hypothalamus. Animals were allowed ad libitum ethanol intake (7.3 ± 1.1 g/kg/day) after a controlled isocaloric pair-feeding period of sucrose and alcoholic diets. Alcohol intake reduced the number of BrdU+ cells in SGZ, SVZ, and hypothalamus. The treatments (URB597, ACEA, JWH133) exerted a differential increase in alcohol consumption over time, but JWH133 specifically counteracted the deleterious effect of ethanol on NPC proliferation in the SVZ and SGZ, and ACEA reversed this effect in the SGZ only. JWH133 also induced an increased number of BrdU+ cells expressing neuron-specific β3-tubulin in the SVZ and SGZ. These results indicated that the specific activation of CB₂ receptors rescued alcohol-induced impaired NPC proliferation, which is a potential clinical interest for the risk of neural damage in alcohol dependence.

Changes in expression of BDNF and its receptors TrkB and p75NTR in the hippocampus of a dog model of chronic alcoholism and abstinence

Chronic ethanol consumption can produce learning and memory deficits. Brain-derived neurotrophic factor (BDNF) and its receptors affect the pathogenesis of alcoholism. In this study, we examined the expression of BDNF, tropomyosin receptor kinase B (TrkB) and p75 neurotrophin receptor (p75NTR) in the hippocampus of a dog model of chronic alcoholism and abstinence. Twenty domestic dogs (9-10 months old, 15-20 kg; 10 males and 10 females) were obtained from Harbin Medical University. A stable alcoholism model was established through ad libitum feeding, and anti-alcohol drug treatment (Zhong Yao Jie Jiu Ling, the main ingredient was the stems of watermelon; developed in our laboratory), at low- and high-doses, was carried out. The Zhong Yao Jie Jiu Ling was effective for the alcoholism in dogs. The morphology of hippocampal neurons was evaluated using hematoxylin-eosin staining. The number and morphological features of BDNF, TrkB and p75NTR-positive neurons in the dentate gyrus (DG), and the CA1, CA3 and CA4 regions of the hippocampus were observed using immunohistochemistry. One-way ANOVA was used to determine differences in BDNF, TrkB and p75NTR expression. BDNF, TrkB and p75NTR-positive cells were mainly localized in the granular cell layer of the DG and in the pyramidal cell layer of the CA1, CA3 and CA4 regions (DG>CA1>CA3>CA4). Expression levels of both BDNF and TrkB were decreased in chronic alcoholism, and increased after abstinence. The CA4 region appeared to show the greatest differences. Changes in p75NTR expression were the opposite of those of BDNF and TrkB, with the greatest differences observed in the DG and CA4 regions.

Studies on a new potential dopaminergic agent: in vitro BBB permeability, in vivo behavioural effects and molecular docking evaluation

2-Amino-N-[2-(3,4-dihydroxy-phenyl)-ethyl]-3-phenyl-propionamide (DA-PHEN) has been previously synthesized to obtain a potential prodrug capable of release dopamine (DA) into CNS. However, DA-PHEN could act per se as a dopaminergic drug. In this study, the permeability transport (Pe), obtained by parallel artificial permeability assay (PAMPA), indicated a low passive transcellular transport (Pe = 0.32 ± 0.01 × 10(-6 )cm/s). Using the Caco-2 cell system, the Papp AP-BL in absorptive direction (3.36 ± 0.02 × 10(-5 )cm/s) was significantly higher than the Papp BL-AP in secretive direction (1.75 ± 0.07 × 10(-5 )cm/s), suggesting a polarized transport. The efflux ratio (Papp AP-BL/Papp BL-AP = 0.52 ± 0.02) indicated a low affinity of DA-PHEN to efflux carriers. The forced swim test highlighted a reduction of immobility time in both pre-test and test sessions (p < 0.0001), with an exacerbation in the number of headshakes and divings in the pretest (p < 0.0001). Morris water maze strengthened the hypothesis that DA-PHEN induces adaptive responses to environmental challenges which are involved on cognitive functions (DA-PHEN versus CTR: escape latency; p < 0.001; distance swum p < 0.001, time spent on target quadrant p < 0.001), without any change in locomotor activity for the administered dose. The molecular docking revealed the interaction of DA-PHEN with the identified D1 site mapping human brain receptor.

Alcohol use across the lifespan: An analysis of adolescent and aged rodents and humans

Adolescence and old age are unique periods of the lifespan characterized by differential sensitivity to the effects of alcohol. Adolescents and the elderly appear to be more vulnerable to many of alcohol's physiological and behavioral effects compared to adults. The current review explores the differential effects of acute alcohol, predominantly in terms of motor function and cognition, in adolescent and aged humans and rodents. Adolescents are less sensitive to the sedative-hypnotic, anxiolytic, and motor-impairing effects of acute alcohol, but research results are less consistent as it relates to alcohol's effects on cognition. Specifically, previous research has shown adolescents to be more, less, and similarly sensitive to alcohol-induced cognitive deficits compared to adults. These equivocal findings suggest that learning acquisition may be differentially affected by ethanol compared to memory, or that ethanol-induced cognitive deficits are task-dependent. Older rodents appear to be particularly vulnerable to the motor- and cognitive-impairing effects of acute alcohol relative to younger adults. Given that alcohol consumption and abuse is prevalent throughout the lifespan, it is important to recognize age-related differences in response to acute and long-term alcohol. Unfortunately, diagnostic measures and treatment options for alcohol dependence are rarely dedicated to adolescent and aging populations. As discussed, although much scientific advancement has been made regarding the differential effects of alcohol between adolescents and adults, research with the aged is underrepresented. Future researchers should be aware that adolescents and the aged are uniquely affected by alcohol and should continue to investigate alcohol's effects at different stages of maturation.

The effects of chronic alcohol self-administration in nonhuman primate brain networks

BACKGROUND

Long-term alcohol abuse is associated with change in behavior, brain structure, and brain function. However, the nature of these changes is not well understood. In this study, we used network science to analyze a nonhuman primate model of ethanol self-administration to evaluate functional differences between animals with chronic alcohol use and animals with no exposure to alcohol. Of particular interest was how chronic alcohol exposure may affect the resting state network.

METHODS

Baseline resting state functional magnetic resonance imaging was acquired in a cohort of vervet monkeys. Animals underwent an induction period where they were exposed to an isocaloric maltose dextrin solution (control) or ethanol in escalating doses over three 30-day epochs. Following induction, animals were given ad libitum access to water and a maltose dextrin solution (control) or water and ethanol for 22 h/d over 12 months. Cross-sectional analyses examined region of interests in hubs and community structure across animals to determine differences between drinking and nondrinking animals after the 12-month free access period.

RESULTS

Animals were classified as lighter (<2.0 g/kg/d) or heavier drinkers (≥2.0 g/kg/d) based on a median split of their intake pattern during the 12-month ethanol free access period. Statistical analysis of hub connectivity showed significant differences in heavier drinkers for hubs in the precuneus, posterior parietal cortices, superior temporal gyrus, subgenual cingulate, and sensorimotor cortex. Heavier drinkers were also shown to have less consistent communities across the brain compared to lighter drinkers. The different level of consumption between the lighter and heavier drinking monkeys suggests that differences in connectivity may be intake dependent.

CONCLUSIONS

Animals that consume alcohol show topological differences in brain network organization, particularly in animals that drink heavily. Differences in the resting state network were linked to areas that are associated with spatial association, working memory, and visuomotor processing.

Acetaldehyde self-administration by a two-bottle choice paradigm: consequences on emotional reactivity, spatial learning, and memory

Acetaldehyde, the first alcohol metabolite, is responsible for many pharmacological effects that are not clearly distinguishable from those exerted by its parent compound. It alters motor performance, induces reinforced learning and motivated behavior, and produces different reactions according to the route of administration and the relative accumulation in the brain or in the periphery. The effective activity of oral acetaldehyde represents an unresolved field of inquiry that deserves further investigation. Thus, this study explores the acquisition and maintenance of acetaldehyde drinking behavior in adult male rats, employing a two-bottle choice paradigm for water and acetaldehyde solution (from 0.9% to 3.2% v/v), over 8 weeks. The behavioral consequences exerted by chronic acetaldehyde intake are assessed by a set of different tests: trials in an open-field arena and elevated-plus maze provided information on both general motor and explorative activity, and anxiety-driven behavioral responses. The Morris water maze allowed the exploration of cognitive processes such as spatial learning and memory. Determination of acetaldehyde levels in the brain was carried out at the end of the drinking paradigm. Our results indicate that rats exposed for the first time to acetaldehyde at 0.9% displayed a regular and stable daily drinking pattern that reached higher values and a "peaks and drops" shaped-trend when acetaldehyde concentration was increased to 3.2%. Accordingly, an increase in acetaldehyde levels in the brain was determined compared to non-acetaldehyde drinking rats. Acetaldehyde intake during the free-choice paradigm exerted an anxiogenic response in the open-field arena and elevated-plus maze, which in turn correlates with an enhancement in cognitive flexibility and spatial orientation skills, when an adaptive response to a stressful environmental challenge was required. These findings further support the idea that acetaldehyde is indeed a centrally active and behaviorally relevant metabolite of alcohol.

Chronic periadolescent alcohol consumption produces persistent cognitive deficits in rhesus macaques

Although human alcoholics exhibit lasting cognitive deficits, it can be difficult to definitively rule out pre-alcohol performance differences. For example, individuals with a family history of alcoholism are at increased risk for alcoholism and are also behaviorally impaired. Animal models of controlled alcohol exposure permit balanced group assignment, thereby ruling out the effects of pre-existing differences. Periadolescent male rhesus macaques (N = 5) consumed alcohol during 200 drinking sessions (M-F) across a 10-month period (mean daily alcohol consumption: 1.38 g/kg/day). A control group (N = 5) consumed a fruit-flavored vehicle during the same period. Spatial working memory, visual discrimination learning and retention and response time behavioral domains were assessed with subtests of the Monkey CANTAB (CAmbridge Neuropsychological Test Automated Battery). Spatial working memory performance was impaired in the alcohol group after 120 drinking sessions (6 mo) in a manner that depended on retention interval. The chronic alcohol animals were also impaired in retaining a visual discrimination over 24 hrs when assessed 6-8 weeks after cessation of alcohol drinking. Finally, the presentation of distractors in the response time task impaired the response time and accuracy of the chronic alcohol group more than controls after 6 months of alcohol cessation. Chronic alcohol consumption over as little as 6 months produces cognitive deficits, with some domains still affected after acute (6-8 wks) and lasting (6 mo) discontinuation from drinking. Animals were matched on alcohol preference and behavioral performance prior to exposure, thus providing strong evidence for the causal role of chronic alcohol in these deficits.

Early handling effect on female rat spatial and non-spatial learning and memory

This study aims at providing an insight into early handling procedures on learning and memory performance in adult female rats. Early handling procedures were started on post-natal day 2 until 21, and consisted in 15 min, daily separations of the dams from their litters. Assessment of declarative memory was carried out in the novel-object recognition task; spatial learning, reference- and working memory were evaluated in the Morris water maze (MWM). Our results indicate that early handling induced an enhancement in: (1) declarative memory, in the object recognition task, both at 1h and 24h intervals; (2) reference memory in the probe test and working memory and behavioral flexibility in the "single-trial and four-trial place learning paradigm" of the MWM. Short-term separation by increasing maternal care causes a dampening in HPA axis response in the pups. A modulated activation of the stress response may help to protect brain structures, involved in cognitive function. In conclusion, this study shows the long-term effects of a brief maternal separation in enhancing object recognition-, spatial reference- and working memory in female rats, remarking the impact of early environmental experiences and the consequent maternal care on the behavioral adaptive mechanisms in adulthood.

Functional role of adult hippocampal neurogenesis as a therapeutic strategy for mental disorders

Adult neurogenesis, the process of generating new neurons from neural stem cells, plays significant roles in synaptic plasticity, memory, and mood regulation. In the mammalian brain, it continues to occur well into adulthood in discrete regions, namely, the hippocampus and olfactory bulb. During the past decade, significant progress has been made in understanding the mechanisms regulating adult hippocampal neurogenesis and its role in the etiology of mental disorders. In addition, adult hippocampal neurogenesis is highly correlated with the remission of the antidepressant effect. In this paper, we discuss three major psychiatric disorders, depression, schizophrenia, and drug addiction, in light of preclinical evidence used in establishing the neurobiological significance of adult neurogenesis. We interpret the significance of these results and pose questions that remain unanswered. Potential treatments which include electroconvulsive therapy, deep brain stimulation, chemical antidepressants, and exercise therapy are discussed. While consensus lacks on specific mechanisms, we highlight evidence which indicates that these treatments may function via an increase in neural progenitor proliferation and changes to the hippocampal circuitry. Establishing a significant role of adult neurogenesis in the pathogenicity of psychiatric disorders may hold the key to potential strategies toward effective treatment.

Acute and chronic ethanol intake: effects on spatial and non-spatial memory in rats

Abusive alcohol consumption produces neuronal damage and biochemical alterations in the mammal brain followed by cognitive disturbances. In this work rats receiving chronic and acute alcohol intake were evaluated in a spontaneous delayed non-matching to sample/position test. Chronic alcohol-treated rats had free access to an aqueous ethanol solution as the only available liquid source from the postnatal day 21 to the end of experiment (postnatal day 90). Acute alcoholic animals received an injection of 2 g/kg ethanol solution once per week. Subjects were evaluated in two tests (object recognition and spatial recognition) based on the spontaneous delayed non-matching to sample or to position paradigm using delays of 1 min, 15 min and 60 min. Results showed that chronic and acute alcohol intake impairs the rats' performance in both tests. Moreover, chronic alcohol-treated rats were more altered than acute treated animals in both tasks. Our results support the idea that chronic and acute alcohol administration during postnatal development caused widespread brain damage resulting in behavioral disturbances and learning disabilities.

Chronic alcohol consumption impairs visuo-spatial associative memory in periadolescent rhesus monkeys

Alcohol abuse in the adult is often preceded by high alcohol consumption during adolescence. Profound changes in brain structure and function occur during this developmental period, therefore alcohol may impact essential cognitive skill development during the formal educational years. The objective of this study was to determine if chronic oral alcohol intake slows acquisition and performance of cognitive tasks in male adolescent rhesus monkeys. Treatment groups (Alcohol, N=4; Control, N=3) were evaluated on bimanual dexterity and tests of visuo-spatial memory and learning adapted from the Cambridge Neuropsychological Test Automated Battery. Animals were trained daily in 30 min sessions and had subsequent access to alcohol/Tang® solutions (Alcohol group) or Tang® only (Control group) Monday through Friday for 11 months. Recordings of brainstem auditory evoked potentials (BSAEP) were conducted periodically before and during the chronic drinking.

RESULTS

Chronic alcohol drinking (ave of 1.78 g/kg alcohol per session) impaired behavioral performance assessed ∼22 h after the prior drinking session. The Alcohol group required more trials than the Control group to reach criterion on the visuo-spatial memory task and showed increased sensitivity to trial difficulty and retention interval. Alcohol animals also had slowed initial acquisition of the bimanual task. The latency of P4 and P5 BSAEP peaks were also delayed in the Alcohol group. Chronic alcohol consumption impaired the acquisition and performance of a spatial memory task and disrupted brainstem auditory processing, thus these results show that repeated alcohol exposure in adolescence interferes with a range of brain functions including complex visuo-spatial mnemonic processing.

Cognitive enhancers for facilitating drug cue extinction: insights from animal models

Given the success of cue exposure (extinction) therapy combined with a cognitive enhancer for reducing anxiety, it is anticipated that this approach will prove more efficacious than exposure therapy alone in preventing relapse in individuals with substance use disorders. Several factors may undermine the efficacy of exposure therapy for substance use disorders, but we suspect that neurocognitive impairments associated with chronic drug use are an important contributing factor. Numerous insights on these issues are gained from research using animal models of addiction. In this review, the relationship between brain sites whose learning, memory and executive functions are impaired by chronic drug use and brain sites that are important for effective drug cue extinction learning is explored first. This is followed by an overview of animal research showing improved treatment outcome for drug addiction (e.g. alcohol, amphetamine, cocaine, heroin) when explicit extinction training is conducted in combination with acute dosing of a cognitive-enhancing drug. The mechanism by which cognitive enhancers are thought to exert their benefits is by facilitating consolidation of drug cue extinction memory after activation of glutamatergic receptors. Based on the encouraging work in animals, factors that may be important for the treatment of drug addiction are considered.

Naturalistic follow-up of co-morbid substance use in schizophrenia: the West London first-episode study

BACKGROUND

The impact of co-morbid substance use in first-episode schizophrenia has not been fully explored.

METHOD

This naturalistic follow-up of a cohort of 152 people with first-episode schizophrenia examined substance use and clinical outcome in terms of symptoms and social and neuropsychological function.

RESULTS

Data were collected on 85 (56%) of the patient cohort after a median period of 14 months. Over the follow-up period, the proportion of smokers rose from 60% at baseline to 64%. While 30% reported lifetime problem drinking of alcohol at baseline, only 15% had problem drinking at follow-up. Furthermore, while at baseline 63% reported lifetime cannabis use and 32% were currently using the drug, by the follow-up assessment the latter figure had fallen to 18.5%. At follow-up, persistent substance users had significantly more severe positive and depressive symptoms and greater overall severity of illness. A report of no lifetime substance use at baseline was associated with greater improvement in spatial working memory (SWM) at follow-up.

CONCLUSIONS

Past substance use may impede recovery of SWM performance in people with schizophrenia in the year or so following first presentation to psychiatric services. The prevalence of substance use other than tobacco tends to diminish over this period, in the absence of specific interventions. Persistent substance use in first-episode schizophrenia is associated with more severe positive and depressive symptoms but not negative symptoms, and should be a target for specific treatment intervention.

Chronic ethanol consumption in rats produces residual increases in anxiety 4 months after withdrawal

The present study investigated the long-term effects of ethanol consumption in rats. Subjects were maintained on either an ethanol (alcohol) (2.7-6.7%, v/v) or an isocaloric liquid control diet for 26 consecutive days (M=13.7 g/kg/day). Testing for working memory was conducted in a Morris water maze (2 trials/day for 8 days) and commenced after either a short (19 days) or long (120 days) abstinence period. This was followed by assessment of 72 h retention of passive avoidance. Animals were killed either 41 (short abstinence) or 152 days (long abstinence) post-ethanol and their brains stained with cresyl violet. Assessments of dorsal-ventral and medial-lateral cortical vertices were measured in sections derived from eight coronal planes extending +4.20 to -4.16 mm from Bregma. Results indicated that subjects in the ethanol/long abstinence group exhibited increased state anxiety due to their propensity to be thigmotaxtic (i.e., wall-hugging) in the water maze. Unfortunately, such a swim pattern precluded assessment of working memory in our subjects. No evidence of ethanol-induced memory decrements were observed on retention of passive avoidance. There was some evidence that animals in the ethanol/long abstinent group suffered cortical thinning and slight compression of the CA1 layer within the hippocampus, although age might have contributed to the former effect. It was concluded that chronic ethanol consumption increases anxiety even after an extended period of withdrawal and may conspire with age to affect cortical integrity.

Red wine antioxidants protect hippocampal neurons against ethanol-induced damage: A biochemical, morphological and behavioral study

Chronic ethanol consumption increases oxidative stress, which accounts for the striking neurological changes seen in this condition. Notwithstanding, there is well-documented evidence that polyphenols, present in grape skin and seeds, exhibit a strong antioxidant activity. As red wine is rich in polyphenols, the aim of the present work was to evaluate their putative protective effects on the hippocampal formation by applying biochemical, morphological and behavioral approaches. Six-month old male Wistar rats were fed with red wine (ethanol content adjusted to 20%) and the results were compared with those from ethanol-treated (20%) rats and pair-fed controls. Biochemical markers of oxidative stress (lipid peroxidation, glutathione levels and antioxidant enzyme activities) were assessed on hippocampal homogenates. Lipofuscin pigment, an end product of lipid peroxidation, was quantified in hippocampal cornu ammonis 1 and 3 (CA1 and CA3) pyramidal neurons using stereological methods. All animals were behaviorally tested on the Morris water maze in order to assess their spatial learning and memory skills. In red wine-treated rats, lipid peroxidation was the lowest while presenting the highest levels of reduced glutathione and an induction of antioxidant enzyme activities. Morphological findings revealed that, contrary to ethanol, red wine did not increase lipofuscin deposition in CA1 and CA3 pyramidal neurons. Besides, red wine-treated animals learned the water maze task at a higher rate than ethanol group and had better performance scores by the end of the training period and on a probe trial. Actually, no significant differences were found between pair-fed controls and red wine-treated rats in morphological and behavioral data. Thus, our findings demonstrate that chronic consumption of red wine, unlike the ethanol solution alone, does not lead to a decline in hippocampal-dependent spatial memory. This may be due to the ability of red wine polyphenols to improve the antioxidant status in the brain and to prevent free radical-induced neuronal damage.

THIS ARTICLE HAS BEEN RETRACTED: Functional nerve growth factor and trkA autocrine/paracrine circuits in adult rat cortex are revealed by episodic ethanol exposure and withdrawal

The hypothesis tested is that cortical neurotrophins communicate through an inducible autocrine/paracrine mechanism. As ethanol (Et) can induce cortical nerve growth factor (NGF) expression, adult rats were challenged with Et on three consecutive days per week for 6 weeks. The focus of the study was layer V, the chief repository of receptor-expressing neuronal cell bodies. Brains were collected immediately after the sixth Et exposure or 72 h later [i.e., following withdrawal (WD)]. Double-label in situ hybridization-immunohistochemistry studies showed that many neuronal somata co-expressed NGF mRNA with NGF, trkA, or phosphorylated trk (p-trk), essential components of an inducible autocrine system. The frequencies of co-labeling were affected by neither Et nor WD. On the contrary, Et increased the number of NGF mRNA-expressing neurons and the amount of NGF mRNA expressed per cell. Et also increased total cortical concentration of NGF protein, the number of layer V neurons expressing trkA transcript, the amount of trkA mRNA expressed per neuron, and trkA phosphorylation. Following WD, the frequency of NGF-mRNA-expressing cells increased, although transcript and protein content fell. WD induced an increase in trkA mRNA and protein expression, however, p-trk expression was unaffected. Thus, Et treatment reveals that layer V has inducible autocrine/paracrine and anterograde neurotrophin systems. WD unveils the dynamism and recruitability of these systems.

Dietary restriction protects against chronic-ethanol-induced changes in exploratory behavior in Wistar rats

Chronic ethanol intake causes various types of neural damage and behavioral impairments, probably acting through oxidative stress and excitotoxicity, while dietary restriction is considered by some authors to protect the central nervous system from these kinds of damage. In the present study, a factorial experimental design was used to investigate the effects of chronic ethanol and dietary restriction treatments, associated or not, on Wistar rats' exploratory behavior, spatial memory aspects and cortical and hippocampal acetylcholinesterase (AChE) activity. Dietary restriction lasted for the whole experiment, while ethanol treatment lasted for only 3 weeks. Despite the short ethanol treatment duration, for two behavior categories assessed, moving and rearing, an interaction was observed between the effects of chronic ethanol and dietary restriction. There were no significant differences in AChE activities among the groups. Cerebellar neural nitric oxide synthase (nNOs) activity was measured as a first step to assess oxidative stress. Dietary restriction significantly reduced NO formation. The present results indicate that dietary restriction might exert a protective effect against chronic-ethanol-induced changes in exploratory behavior. It is hypothesized that the mechanisms underlying this protection can involve prevention of oxidative stress.

Adolescent Rats Exposed to Repeated Ethanol Treatment Show Lingering Behavioral Impairments

BACKGROUND

Repeated ethanol treatment has been reported to differentially affect water maze performance in adolescent and adult rats. The present study was undertaken to determine the age-specific reversal of ethanol-induced deficit in water maze performance.

METHODS

Adolescent and adult male rats were subjected to repeated ethanol or saline treatments. Experimental rats were injected daily with 2 g/kg ethanol (intraperitoneally) for five consecutive days (Days 1-5) and tested in the hidden platform task of the Morris water maze 30 minutes after ethanol treatment; control rats received isovolumetric saline. On the last training day, all rats were tested in the probe trial and in the cued visual task. After an ethanol-free period of 4-25 days, rats were retested in the water maze.

RESULTS

Adolescent ethanol-treated rats had significantly higher latencies and swam greater distances to find the hidden platform, compared to age-matched saline control rats. Ethanol rats also showed increased hug time, i.e., spent significantly more time near the periphery of the pool than control rats. In the probe trial, compared to adolescent saline rats, ethanol rats spent less time in the target quadrant. However, there was no difference between ethanol- and saline-treated rats in the swim speed or in the visual task performance. Experimental and control rats were retested in the water maze 4 days (Day 9), 7 days (Day 12), and 25 days (Day 30) after the last ethanol/saline treatment; no injections were given on those days. Ethanol-treated rats continued to do poorly on all retest days. Ethanol treatment in adult male rats acutely increased latency and distance to find the hidden platform, but unlike adolescent alcohol rats, their performance in the probe trial did not differ from adult saline rats. Also, swim speed and visual task performance of adult rats were significantly affected by ethanol exposure. During retesting, their performance did not differ from adult control rats.

CONCLUSIONS

Adolescent rats exposed to ethanol showed deficits in water maze performance, had increased hug time, and failed to catch up with control rats during the weeks after the ethanol treatment period was over. Adult alcohol rats showed some behavioral dysfunction (increased latency and distance to find the hidden platform) but had problems swimming, and in the probe trial they performed as well as control rats. Also, in adult rats, ethanol-induced impairments were quickly reversed after the ethanol treatment was over, a finding that suggests impaired motor coordination more than a true learning deficit. Together, these data indicate that repeated ethanol treatment in adolescent rats, but not adult rats, show long-term impairments in maze performance.

Cholinergic parameters and the retrieval of learned and re-learned spatial information: a study using a model of Wernicke-Korsakoff Syndrome

This is a factorial (2 x 2 x 2) spatial memory and cholinergic parameters study in which the factors are chronic ethanol, thiamine deficiency and naivety in Morris water maze task. Both learning and retention of the spatial version of the water maze were assessed. To assess retrograde retention of spatial information, half of the rats were pre-trained on the maze before the treatment manipulations of pyrithiamine (PT)-induced thiamine deficiency and post-tested after treatment (pre-trained group). The other half of the animals was only trained after treatment to assess anterograde amnesia (post-trained group). Thiamine deficiency, associated to chronic ethanol treatment, had a significant deleterious effect on spatial memory performance of post-trained animals. The biochemical data revealed that chronic ethanol treatment reduced acetylcholinesterase (AChE) activity in the hippocampus while leaving the neocortex unchanged, whereas thiamine deficiency reduced both cortical and hippocampal AChE activity. Regarding basal and stimulated cortical acetylcholine (ACh) release, both chronic ethanol and thiamine deficiency treatments had significant main effects. Significant correlations were found between both cortical and hippocampal AChE activity and behaviour parameters for pre-trained but not for post-trained animals. Also for ACh release, the correlation found was significant only for pre-trained animals. These biochemical parameters were decreased by thiamine deficiency and chronic ethanol treatment, both in pre-trained and post-trained animals. But the correlation with the behavioural parameters was observed only for pre-trained animals, that is, those that were retrained and assessed for retrograde retention.

Repeated episodic exposure to ethanol affects neurotrophin content in the forebrain of the mature rat

Chronic exposure to ethanol can cause deficits in learning and memory. It has been suggested that withdrawal is potentially more damaging than the ethanol exposure per se. Therefore, we explored the effect of repeated episodic exposure to ethanol on key regulators of cortical activity, the neurotrophins. Rats were exposed to ethanol via a liquid diet for 3 days per week for 6-24 weeks. Control rats were pair-fed an isocaloric liquid diet or ad libitum fed chow and water. The concentrations of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) were determined using enzyme-linked immunosorbant assays (ELISAs). Five telencephalic structures were examined: parietal cortex, entorhinal cortex, hippocampus, the basal nucleus, and the septal nuclei. All five areas expressed each of the three neurotrophins; BDNF was most abundant and NGF the least. The parietal cortex was susceptible to ethanol exposure, NGF and BDNF content increased, and NT-3 content fell, whereas no changes were detectable in the entorhinal cortex. In the hippocampus, the amount all three neurotrophins increased following episodic ethanol exposure. Neurotrophin content in the two segments of the basal forebrain was affected; NGF and NT-3 content in the basal forebrain was reduced and NGF and BDNF content in the septal nuclei was increased by ethanol exposure. In many cases where ethanol had an effect, the change was transient so that by 24 weeks of episodic exposure, no significant changes were evident. Thus, the effects of ethanol are site- and time-dependent. This pattern differs from changes caused by chronic ethanol exposure, hence, neurotrophins must be vulnerable to the effects of withdrawal. Furthermore, the ethanol-induced changes do not appear to fit a model consistent with retrograde regulation, rather they suggest that neurotrophins act through autocrine/paracrine systems.

Residual behavioral and neuroanatomical effects of short-term chronic ethanol consumption in rats

The residual effects of short-term chronic ethanol consumption were investigated in rats maintained on an ethanol liquid diet for 26 consecutive days (mean intake = 16.1 g/kg/day). Animals were assessed for spontaneous motor activity (12 days post-ethanol), spatial working memory (17 days post-ethanol), spatial reference memory (184 days post-ethanol), and retention of passive avoidance (201 days post-ethanol). Measurements of brain weights and cortical thickness vertices within the dorsomedial and ventrolateral cortex of eight coronal planes were determined 260 days post-ethanol. Two-dimensional cell profile densities within six coronal planes and within CA1 region of the hippocampus were also obtained, along with the total volumetric measurement of the hippocampus proper. Results indicated between group differences when subjects were assessed on working memory with ethanol-treated animals exhibiting longer escape latencies in a Morris water maze, an effect partially attributed to the perseverance of ethanol-treated animals in exhibiting thigmotaxicity. No other ethanol-related behavioral impairment was noted. Neuroanatomically, ethanol-treated rats had thinner cortical mantles (6.3% and 6.6% reductions) within the frontoparietal cortex and had lower two-dimensional cell profile densities within the most caudal cortical region studied. Interestingly, control animals with thicker cortical mantles tended to perform better on the working memory task, whereas the opposite was true for ethanol-treated subjects. These data led to the conclusion that chronic ethanol consumption of a relatively short duration produces working memory impairments, albeit mild, that are partially related to an inability to abandon ineffectual behavioral strategies, and also produces neuroanatomical alterations within the cortex.

Chronic exposure to ethanol alters neurotrophin content in the basal forebrain-cortex system in the mature rat: Effects on autocrine-paracrine mechanisms

Neurotrophins are broadly expressed in the mammalian forebrain: notably in cerebral cortex and the basal forebrain (e.g., the septal and basal nuclei). These factors promote neuronal survival and plasticity, and have been implicated as key players in learning and memory. Chronic exposure to ethanol causes learning and memory deficits. We tested the hypothesis that ethanol affects neurotrophin expression and predicted that these changes would be consistent with alterations in retrograde or autocrine/paracrine systems. Mature rats were fed a liquid diet containing ethanol daily for 8 or 24 weeks. Weight-matched controls were pair-fed an isocaloric, isonutritive diet. Proteins from five structures (parietal and entorhinal cortices, hippocampus, and the basal and septal nuclei) were studied. ELISAs were used to determine the concentration of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). All three neurotrophins were detected in each structure examined. Ethanol treatment significantly (p < 0.05) affected neurotrophin expression in time- and space-dependent manners. NGF content was generally depressed by ethanol exposure, whereas NT-3 content increased. BDNF concentration was differentially affected by ethanol: it increased in the parietal cortex and the basal forebrain and decreased in the hippocampus. With the exception of NGF in the septohippocampal system, the ethanol-induced changes in connected structures were inconsistent with changes that would be predicted from a retrograde model. Thus, the present data (a) support the concept that neurotrophins act through a nonretrograde system (i.e., a local autocrine/paracrine system), and (b) that chronic exposure to ethanol disrupts these regulatory mechanisms.

Selective impairment of hippocampal neurogenesis by chronic alcoholism: protective effects of an antioxidant

A major pathogenic mechanism of chronic alcoholism involves oxidative burden to liver and other cell types. We show that adult neurogenesis within the dentate gyrus of the hippocampus is selectively impaired in a rat model of alcoholism, and that it can be completely prevented by the antioxidant ebselen. Rats fed for 6 weeks with a liquid diet containing moderate doses of ethanol had a 66.3% decrease in the number of new neurons and a 227-279% increase in cell death in the dentate gyrus as compared with paired controls. Neurogenesis within the olfactory bulb was not affected by alcohol. Our studies indicate that alcohol abuse, even for a short duration, results in the death of newly formed neurons within the adult brain and that the underlying mechanism is related to oxidative or nitrosative stress. Moreover, these findings suggest that the impaired neurogenesis may be a mechanism mediating cognitive deficits observed in alcoholism.

Ethanol-induced impairment of spatial memory and brain matrix metalloproteinases

The formation of spatial memory appears to be dependent upon an intact hippocampus capable of the specific biochemical changes associated with synaptic remodeling. Hippocampal damage results in the disruption of synaptic remodeling and the acquisition of spatial memory tasks. Ethanol also disrupts normal hippocampal functioning and spatial memory. The present investigation established a dose-response relationship between ethanol treatment and impairment of spatial memory as measured using the circular water maze task. Intraperitoneal ethanol doses of 1.5 and 2 g/kg significantly increased the latency and distance swam to find the submerged pedestal as compared with a 1 g/kg dose, and 0.15 M NaCl vehicle control treatments. On days 2, 4, and 6 of acquisition animals were sacrificed and brain tissues were retained from the hippocampus, prefrontal neocortex, and cerebellum for measurement of matrix metalloproteinases (MMPs). The results indicated that ethanol treatment interfered with MMP-9, but not MMP-2, activity in the hippocampus, and to a lesser degree in the prefrontal cortex. No changes in the cerebellum were measured. Elevations in MMP activity appear to be a prerequisite to reconfiguration of extracellular matrix cell adhesion molecules thought to be important in the process of synaptic plasticity, which in turn appears to be necessary for memory consolidation. Thus, ethanol-induced impairment in the acquisition of spatial memory tasks may, in part, be due to disruption of brain MMP activity.

Chronic ethanol consumption induces tolerance to the spatial memory impairing effects of acute ethanol administration in rats

A large number of studies in rats have investigated the effects of acute and chronic ethanol administration on performance on many spatial learning and memory tasks. However, no study has addressed the problem of whether chronic ethanol consumption induces tolerance to acute ethanol-induced spatial memory deficits. In this study, we analyzed the behavioral effects of acute ethanol administration on spatial memory and locomotor activity in rats chronically intoxicated by ethanol. Male Sprague-Dawley rats were given as their only available liquid source a 10% (v/v) aqueous ethanol solution for 2 weeks before behavioral testing and during the 1-week behavioral testing period. They were treated intraperitoneally with 1.5 g/kg of ethanol 30 min before daily training in the Morris water maze, a spatial memory task sensitive to hippocampal damage. Our results demonstrate that learning and spatial memory of ethanol-consuming animals were not altered compared with control rats. Chronic ethanol consumption had no effect on spatial reference memory in terms of either the distance traveled to find the hidden platform during the acquisition phase of the experiment, or the time spent in the training quadrant during the retention trial. Acute ethanol administration impaired spatial memory in control rats and this impairment was reversed in chronic ethanol-consuming animals, revealing that chronic ethanol consumption did induce tolerance to the spatial memory deficits induced by acute ethanol injection, although plasma ethanol levels did not differ between the two groups. In contrast, chronic ethanol consumption did not induce tolerance to the acute ethanol-induced stimulatory locomotor activity measured in the same animals. Our results, therefore, indicate that chronic ethanol consumption induces tolerance to the cognitive impairing effects, but not to the locomotor stimulatory effects of acute ethanol administration in rats, suggesting that these two behavioral effects of ethanol do not share a common mechanism in the CNS.

The effects of chronic ethanol consumption on neurotrophins and their receptors in the rat hippocampus and basal forebrain

Damage to the basal forebrain frequently results in deficits in learning and memory. Mnenonic dysfunction also occurs following prolonged ethanol consumption in humans and in animal models of chronic ethanol intake, accompanied by specific abnormalities in synaptic transmission between the basal forebrain and hippocampus. The integrity of at least some of the reciprocal neuronal connections between these brain regions is influenced by target-derived neurotrophic factors. We used a semiquantitative reverse transcription polymerase chain reaction technique to measure the messenger RNA for neurotrophins BDNF and NGF, and for their receptors trkB, trkA, and the low affinity receptor, p75(NTR) in the hippocampus and basal forebrain of rats after 28 weeks of alcohol consumption without malnutrition. This chronic ethanol treatment (CET) resulted in a marked and selective reduction in basal forebrain trkA mRNA. Western blotting revealed a similar reduction of basal forebrain trkA protein. CET effects on basal forebrain trkA may reflect impaired NGF signaling that could compromise septohippocampal synaptic connections, cholinergic differentiation, and emergent functional abilities dependent on these properties.