Long-term voluntary ethanol consumption affects neither spatial nor passive avoidance learning, nor hippocampal acetylcholine release in alcohol-preferring rats

The short-term improvements of enriched environment in behaviors and pathological changes of APP/PS1 mice via regulating cytokines

OBJECTIVE

To study the effect of enriched environment (EE) on cognitive function and pathological changes in Alzheimer's disease (AD) mice.

METHOD

6-month-old of the male mice were divided into 3 groups (n = 8), the wild type C57BL/6 mice in the control group, the APP/PS1 transgenic mice of AD reared in either the standard environment or the EE. Mice were feeding for 8 weeks, and then moved into standard environment. The activity and cognitive function were measured by Open-field test and Morris-water Maze. Immunofluorescence was used to detect Aβ plaque, hydroxylamine colorimetric assay was used to detect the activity of Ach, ChAT and AchE, and ELISA was used to detect the Aβ protein and the inflammatory factors IL-1β, IL-6, TNF-α and IFN-γ in serum, as well as the trophic cytokines BDNF, NGF and IGF-1 in hippocampus.

RESULT

Compared with the controls, the behaviors of AD mice were degraded, the Aβ deposition could be detected in the brain, the activity of Ach and ChAT decreased while the AchE increased, and the inflammatory factors increased significantly in serum while the trophic factors decreased in hippocampus. By means of rearing in EE, the activity and cognitive functions of AD mice were improved, and the Aβ plaques were significantly reduced. Meanwhile, the inflammatory factors in serum were reduced while the trophic cytokines increased. Besides, the cholinergic system in the brain were improved without statistic difference. However, 3 months later, these improvements in AD mice which were previously raised in EE disappeared.

CONCLUSION

The EE can improve the behaviors of AD mice, reduce the Aβ deposition in the brain, regulate the levels of cytokines, and have benefit in pathological changes in AD, but these improvements are short-term.

Novel candidate genes for alcoholism--transcriptomic analysis of prefrontal medial cortex, hippocampus and nucleus accumbens of Warsaw alcohol-preferring and non-preferring rats

OBJECTIVE

Animal models provide opportunity to study neurobiological aspects of human alcoholism. Changes in gene expression have been implicated in mediating brain functions, including reward system and addiction. The current study aimed to identify genes that may underlie differential ethanol preference in Warsaw High Preferring (WHP) and Warsaw Low Preferring (WLP) rats.

METHODS

Microarray analysis comparing gene expression in nucleus accumbens (NAc), hippocampus (HP) and medial prefrontal cortex (mPFC) was performed in male WHP and WLP rats bred for differences in ethanol preference.

RESULTS

Differential and stable between biological repeats expression of 345, 254 and 129 transcripts in NAc, HP and mPFC was detected. Identified genes and processes included known mediators of ethanol response (Mx2, Fam111a, Itpr1, Gabra4, Agtr1a, LTP/LTD, renin-angiotensin signaling pathway), toxicity (Sult1c2a, Ces1, inflammatory response), as well as genes involved in regulation of important addiction-related brain systems such as dopamine, tachykinin or acetylcholine (Gng7, Tac4, Slc5a7).

CONCLUSIONS

The identified candidate genes may underlie differential ethanol preference in an animal model of alcoholism.

COMMENT

Names of genes are written in italics, while names of proteins are written in standard font. Names of human genes/proteins are written in all capital letters. Names of rodent genes/proteins are written in capital letter followed by small letters.

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.

Effects of electroacupuncture on ethanol-induced impairments of spatial learning and memory and Fos expression in the hippocampus in rats

It is well established that alcohol impairs spatial learning and memory. Here, we investigated the effects of electroacupuncture (EA) at ST36 or nonacupoint on ethanol-induced learning and memory impairment and the expression of Fos in the hippocampus. Ethanol (5g/kg) was administered intragastrically once a day for 5 consecutive days; 2Hz EA was administered immediately after ethanol exposure. After a 2-day ethanol abstinence, for 6 consecutive days, the rats were submitted to Morris water maze training. Probe trials were performed on 1 day after the final training session. We also applied immunohistochemistry to detect Fos-positive nuclei in the hippocampus. We found that 5-day ethanol exposure markedly decreased spatial learning and memory abilities in the Morris water maze task as indicated by escape latency and time in the target quadrant. EA treatment shortened the time of reaching platform and increased times traveled in the target quadrant (P<0.05). Animals administered with ethanol emitted significantly fewer Fos expression in the hippocampal CA1 area. EA increased Fos expression in the hippocampal CA1 area. Significant correlations were obtained between Fos protein expression in CA1 and time in the target quadrant. Altogether, these results suggest that EA protects against ethanol-induced impairments of spatial learning and memory, which may be involved in the hippocampal CA1 area. EA treatment may provide a novel nonpharmacological strategy for ethanol-induced learning and memory impairment.

Mild thiamine deficiency and chronic ethanol consumption modulate acetylcholinesterase activity change and spatial memory performance in a water maze task

Chronic thiamine deficiency may be responsible for pathologic changes in the brains of alcoholics, and subclinical episodes of this vitamin deficiency may cause cumulative brain damage. In the present work, the chronic effects of ethanol and its association to a mild thiamine deficiency episode (subclinical model) on neocortical and hippocampal acetylcholinesterase activity were assessed along with their possible association to spatial cognitive dysfunction. The results indicate that in the beginning of the neurodegenerative process, before the appearance of brain lesions, chronic ethanol consumption reverses the effects of mild thiamine deficiency on both spatial cognitive performance and acetylcholinesterase activity without having significant effects on any morphometric parameter.

Effects of different exercise protocols on ethanol-induced spatial memory impairment in adult male rats

Chronic ethanol consumption is often accompanied by numerous cognitive deficits and may lead to long-lasting impairments in spatial learning and memory. The aim of the present study was to evaluate the therapeutic potential of regular treadmill exercise on hippocampal-dependent memory in ethanol-treated rats. Spatial memory was tested in a Morris Water Maze task. Adult male Wistar rats were exposed to ethanol (4 g/kg, 20% v/v for 4 weeks) and effects of three exercise protocols (pre-ethanol, post-ethanol and pre-to-post-ethanol treatment) were examined. Results showed that ethanol exposure resulted in longer escape latencies during the acquisition phase of the Morris Water Maze task. Moreover, all three exercise protocols significantly decreased the latency to locate the hidden platform. During the probe trial, ethanol led to decreased time spent in the target quadrant. In contrast, performance on the probe trial was significantly better in the rats that had done the post- and pre-to-post-ethanol, but not pre-ethanol, exercises. These findings suggest that treadmill running can attenuate the adverse effects of chronic ethanol exposure on spatial memory, and may serve as a non-pharmacological alcohol abuse treatment.

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.

Increase in alcohol intake, reduced flexibility of alcohol drinking, and evidence of signs of alcohol intoxication in Sardinian alcohol-preferring rats exposed to intermittent access to 20% alcohol

BACKGROUND

This study assessed in Sardinian alcohol-preferring (sP) rats a procedure known to promote alcohol drinking and based on the intermittent (once every other day) access to 2 bottles containing alcohol (20%, v/v) and water, respectively (Wise, 1973).

METHODS

To this end, sP rats were exposed - under the 2-bottle choice regimen - to: (i) 10% (v/v) alcohol with continuous access (CA10%; i.e., the procedure under which sP rats had been selectively bred); (ii) 10% (v/v) alcohol with intermittent access (IA10%); (iii) 20% (v/v) alcohol with continuous access (CA20%); (iv) 20% (v/v) alcohol with intermittent access (IA20%; the "Wise" condition) (Experiment 1). Additional experiments assessed the influence of (i) adulteration with quinine of the alcohol solution (Experiment 2) and (ii) concurrent presentation of a saccharin solution (Experiment 3) on alcohol drinking under the CA10% and IA20% conditions. Finally, it was assessed whether alcohol drinking under the CA10% and IA20% conditions resulted in motor incoordination at the Rota-Rod task, as a possible sign of alcohol intoxication (Experiment 4).

RESULTS

Daily alcohol intake markedly escalated in rats exposed to the IA20% condition, averaging 9.0 g/kg (in comparison with the average intake of 6.5 g/kg in the CA10% rat group). CA20% and IA10% rats displayed intermediate values of daily alcohol intake between those of CA10% and IA20% rats. Alcohol intake was virtually abolished by addition of quinine or by concurrent presentation of the saccharin solution in CA10% rats; conversely, alcohol intake in IA20% rats was only partially affected by gustatory aversion or concurrent presentation of an alternative reinforcer. Finally, alcohol intake in IA20%, but not in CA10%, rats resulted in clear motor-incoordinating effects.

CONCLUSIONS

These data suggest that the "Wise" procedure is effective in inducing marked increases in alcohol intake in sP rats. These increases are associated with a reduced flexibility of alcohol drinking (suggesting the development of "behavioral" dependence) and produce signs of alcohol intoxication that are not detected when sP rats are exposed to the more conventional CA10% condition.

The influence of alcohol on behavioral recovery after mTBI in mice

In the United States 258,000 people were injured in 2004 in motor vehicle accidents that were caused by drivers under the influence of alcohol. The majority of these drivers were binge drinkers, most notably young people who tend to drink heavily during the weekends, but rarely drink alcohol during the week. Since a large proportion of the injuries involved head injuries, the present study aimed at investigating the influence of binge alcohol drinking on mild traumatic brain injury (mTBI) in an animal model. Mice had access to 0%, 7.5%, 15%, or 30% alcohol solutions for 48 consecutive hours once a week for 4 weeks as the sole source of fluids (the remaining time they drank water). Three experiments were done. For the first one (alcohol-mTBI-alcohol) the animals were subjected to a controlled mTBI injury by applying a closed-head weight drop, or a sham procedure. After the mTBI/sham-mTBI the animals got alcohol and /water for the same regimen for 4 additional weeks. In the second experiment (alcohol only) after the 4 weeks of drinking blood samples were collected, at the same time as the animals that underwent sham-mTBI or mTBI procedures. In the third experiment (mTBI-alcohol) the mice were subjected to mTBI/sham-mTBI without any treatment, and after mTBI they had alcohol for 4 weeks in the same regimen as in the previous experiments. At the end of the pharmacological treatment all animals were assessed using different behavioral tests. mTBI mice exhibited lower memory ability in the Y-maze, higher anxiety in the elevated plus maze, and lower retention in the passive avoidance test than sham-mTBI animals. Alcohol reversed these effects at all doses. The results suggest that alcohol drinking before trauma might have a protective effect on recovery from brain trauma, but not if consumed after the trauma.

Intrahippocampal nicotine in alcohol drinking rats--effects on lever-press response

We have previously shown differences on learning processes between alcohol drinking and non-alcohol drinking rats. Underlying these effects, functional differences in the septo-hippocampal pathway were hypothesized. We have performed a dose-response study for intrahippocampal nicotine (CA1) on acquisition and extinction of the lever-press response and antagonization test by co-administration of mecamylamine. Results show that the administration of nicotine in CAI region has a detrimental dose-dependent effect on acquisition in alcohol drinkers, with a dose of 10 nM being the most disruptive. In the controls, only doses of 10 and 20 nM had detrimental effect. The effect of nicotine (10 nM) was partially (alcoholics) or fully (controls) antagonized by mecamylamine co-administration (30 nM). Summarizing, the alcohol groups showed a dose-response curve for nicotine shifted leftwards, and a partial antagonism of these effects by mecamylamine; these effects may be consequence of the functional sensitization of the nicotinic responsivity in the CAI region which were produced by the chronic alcohol.

Chronic ethanol consumption does not affect action of propofol on rat hippocampal acetylcholine release in vivo

BACKGROUND

The aim of this study was to examine ethanol-consumption-related changes in the effects of propofol on rat hippocampal acetylcholine (ACh) release.

METHODS

Male Sprague-Dawley rats received a solution of ethanol (20% v/v) for 24 weeks while controls received tap water. The effects of propofol were examined by in vivo microdialysis, with ACh release from the hippocampal regions determined by high-performance liquid chromatography with electrochemical detection (HPLC-ECD).

RESULTS

Propofol 50 mg kg(-1) i.p. significantly decreased basal hippocampal ACh release in ethanol-treated and control rats by 50.4 (sem 4.7)% and 38.3 (11.1)%, respectively. Propofol 100 mg kg(-1) i.p. significantly decreased basal hippocampal ACh release in ethanol-treated and control rats by 67.5 (3.7)% and 55.9 (7.4)%, respectively. The reduction in hippocampal ACh release induced by 50 or 100 mg kg(-1) i.p. propofol was not significantly different between ethanol-treated and control rats. There was no significant difference in the duration of sleep between the two groups.

CONCLUSIONS

These results demonstrate that chronic ethanol consumption does not augment the inhibitory actions of propofol on rat hippocampal ACh release. These findings appear to be inconsistent with the notion that chronic ethanol intake enhances the propofol-induced inhibition of the hippocampal cholinergic system and related mental dysfunction.

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.

Immediate and delayed voluntary ethanol effects on motor performance, learning and inhibition in rats

The effects of prolonged voluntary ethanol consumption on psychomotor performance, operant conditioning and inhibition were examined in adult male Wistar rats. Animals were food deprived and alcohol or control solution was available 1 h/day during 15 days, with free water for the rest of the day. Then, rats were tested in a two-bottle paradigm (solution and water available) for 1 h/day during 19 days, and subjects were tested daily for psychomotor performance and operant conditioning immediately or 6 h after (delayed) the solution access. Psychomotor performance was tested in an 80 degrees -inclined screen. Successive conditioning phases were: free shaping (FS), continuous reinforcement (CRF), operant extinction (EXT), successive discrimination (DIS) and two-stimuli test (TST). Alcohol consumption deteriorated psychomotor performance and improved the animal's ability to learn simple associations between stimuli and responses (free shaping and extinction), in immediate and delayed groups. Finally, alcohol deteriorated behavioral inhibition (DIS and TST) tested immediately after drinking. Taken together, results suggest that prolonged voluntary ethanol intake could induce permanent psychomotor impairment and associative learning facilitation, and also an impairment of the inhibition related to the intoxication state.