Sardinian alcohol-preferring rats prefer chocolate and sucrose over ethanol

Exposure to an enriched environment reduces alcohol self-administration in Sardinian alcohol-preferring rats

Living in an enriched environment (EE) produces a notable impact on several rodent behaviors, including those motivated by drugs of abuse. This picture is somewhat less clear when referring to alcohol-motivated behaviors. With the intent of contributing to this research field with data from one of the few rat lines selectively bred for excessive alcohol consumption, the present study investigated the effect of EE on operant oral alcohol self-administration in Sardinian alcohol-preferring (sP) rats. Starting from Postnatal Day (PND) 21, male sP rats were kept under 3 different housing conditions: impoverished environment (IE; single housing in shoebox-like cages with no environmental enrichment); standard environment (SE; small colony cages with 3 rats and no environmental enrichment); EE (large colony cages with 6 rats and multiple elements of environmental enrichment, including 2 floors, ladders, maze, running wheels, and shelter). From PND 60, rats were exposed to different phases of shaping and training of alcohol self-administration. IE, SE, and EE rats were then compared under (i) fixed ratio (FR) 4 (FR4) schedule of alcohol reinforcement for 20 daily sessions and (ii) progressive ratio (PR) schedule of alcohol reinforcement in a final single session. Acquisition of the lever-responding task (shaping) was slower in EE than IE and SE rats, as the likely consequence of a "devaluation" of the novel stimuli provided by the operant chamber in comparison to those to which EE rats were continuously exposed in their homecage or an alteration, induced by EE, of the rat "emotionality" state when facing the novel environment represented by the operant chamber. Training of alcohol self-administration was slower in EE than IE rats, with SE rats displaying intermediate values. A similar ranking order (IE>SE>EE) was also observed in number of lever-responses for alcohol, amount of self-administered alcohol, and breakpoint for alcohol under FR4 and PR schedules of reinforcement. These data suggest that living in a complex environment reduced the reinforcing and motivational properties of alcohol in sP rats. These results are interpreted in terms of the reinforcing and motivational properties of the main components of EE (i.e., social interactions, physical activities, exploration, novelty) substituting, at least partially, for those of alcohol.

Behavioral, neurobiological, and neurochemical mechanisms of ethanol self-administration: A translational review

Alcohol use disorder has multiple characteristics including excessive ethanol consumption, impaired control over drinking behaviors, craving and withdrawal symptoms, compulsive seeking behaviors, and is considered a chronic condition. Relapse is common. Determining the neurobiological targets of ethanol and the adaptations induced by chronic ethanol exposure is critical to understanding the clinical manifestation of alcohol use disorders, the mechanisms underlying the various features of the disorder, and for informing medication development. In the present review, we discuss ethanol's interactions with a variety of neurotransmitter systems, summarizing findings from preclinical and translational studies to highlight recent progress in the field. We then describe animal models of ethanol self-administration, emphasizing the value, limitations, and validity of commonly used models. Lastly, we summarize the behavioral changes induced by chronic ethanol self-administration, with an emphasis on cue-elicited behavior, the role of ethanol-related memories, and the emergence of habitual ethanol seeking behavior.

Consumption of Substances of Abuse during Pregnancy Increases Consumption in Offspring: Possible Underlying Mechanisms

Correlative human observational studies on substances of abuse have been highly dependent on the use of rodent models to determine the neuronal and molecular mechanisms that control behavioral outcomes. This is particularly true for gestational exposure to non-illicit substances of abuse, such as excessive dietary fat, ethanol, and nicotine, which are commonly consumed in our society. Exposure to these substances during the prenatal period has been shown in offspring to increase their intake of these substances, induce other behavioral changes, and affect neurochemical systems in several brain areas that are known to control behavior. More importantly, emerging studies are linking the function of the immune system to these neurochemicals and ingestion of these abused substances. This review article will summarize the prenatal rodent models used to study developmental changes in offspring caused by prenatal exposure to dietary fat, ethanol, or nicotine. We will discuss the various techniques used for the administration of these substances into rodents and summarize the published outcomes induced by prenatal exposure to these substances. Finally, this review will cover some of the recent evidence for the role of immune factors in causing these behavioral and neuronal changes.

Low copulatory activity in selectively bred Sardinian alcohol-nonpreferring (sNP) relative to alcohol-preferring (sP) rats

BACKGROUND

There is a growing consensus that similar neural mechanisms are involved in the reinforcing properties of natural rewards, like food and sex, and drugs of abuse. Rat lines selectively bred for high and low oral alcohol intake and preference have been useful for understanding factors contributing to excessive alcohol intake and may constitute proper animal models for investigating the neurobiological basis of natural rewarding stimuli.

METHODS

The present study evaluated copulatory behavior in alcohol and sexually naïve Sardinian alcohol-preferring (sP) and -nonpreferring (sNP) male rats in three consecutive copulatory behavior tests.

RESULTS

The main finding was that, under the conditions used in this study, sNP rats were sexually inactive relative to sP rats. To gain more information about the sexual behavior in sP rats, Wistar rats were included as an external reference strain. Only minor differences between sP and Wistar rats were revealed.

CONCLUSIONS

The reason behind the low copulatory activity of sNP rats remains to be elucidated, but may in part be mediated by innate differences in brain transmitter systems. The comparison between sP and Wistar rats may also suggest that the inherent proclivity to excessive alcohol drinking in sP rats may mainly be dependent on its anxiolytic properties, as previously proposed, and not changes in the reward system.

Advances in animal models of drug addiction

Drug addiction is a syndrome of impaired response inhibition and salience attribution, which involves a complex neurocircuitry underlying drug reinforcement, drug craving, and compulsive drug-seeking and drug-taking behaviors despite adverse consequences. The concept of disease stages with transitions from acute rewarding effects to early- and end-stage addiction has had an important impact on the design of nonclinical animal models. This chapter reviews the main advances in nonclinical paradigms that aim to at model (1) positive and negative reinforcing effects of addictive drugs; (2) relapse to drug-seeking behavior; (3) reconsolidation of drug cue memories, and (4) compulsive/impulsive drug intake. In addition, recent small animal neuroimaging studies and invertebrate models will be briefly discussed (see also Bifone and Gozzi, Animal models of ADHD, 2011). Continuous improvement in modeling drug intake, craving, withdrawal symptoms, relapse, and comorbid psychiatric associations is a necessary step to better understand the etiology of the disease and to ultimately foster the discovery, validation and optimization of new efficacious pharmacotherapeutic approaches. The modeling of specific subprocesses or constructs that address clinically defined criteria will ultimately increase our understanding of the disease as a whole. Future research will have to address the questions of whether some of these constructs can be reliably used as outcome measures to assess the effects of a treatment in clinical settings, whether changes in those measures can be a target of therapeutic efforts, and whether they relate to biological markers of traits such as impulsivity, which contribute to increased drug-seeking and may predict binge-like patterns of drug intake.

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.

Effect of concurrent saccharin intake on ethanol consumption by high-alcohol-drinking (UChB) rats

This study examined the effect of concurrent presentation of a highly palatable saccharin solution on ethanol consumption during the acquisition or maintenance of ethanol drinking by high-alcohol-drinking (UChB) rats. Rats were exposed to ethanol (10% v/v) and water under a home cage, two-bottle, free-choice regimen with unlimited access for 24 hours/day. After 7 days (acquisition) of ethanol exposure, a third bottle containing saccharin (0.2% w/v) was concomitantly offered for an additional seven consecutive days, and the same process was repeated after 3 months (maintenance) of ethanol exposure. We found that concurrent saccharin intake significantly reduced ethanol intake by UChB rats after 7 days of ethanol exposure indicating that preference for sweet taste tends to override the preference for ethanol. However, the concurrent saccharin presentation to rats after 3 months of stable ethanol consumption did not reduce ethanol intake, whereas their saccharin consumption reached polydipsic-like values. These results support the notion that in UChB rats, a time-dependent sensitization to the rewarding effects of ethanol is developed that may account for the increases in ethanol volition seen following chronic ethanol intake.

Effects of alcohol and saccharin deprivations on concurrent ethanol and saccharin operant self-administration by alcohol-preferring (P) rats

Consumption of sweet solutions has been associated with a reduction in withdrawal symptoms and alcohol craving in humans. The objective of the present study was to determine the effects of ethanol and saccharin (SACC) deprivations on operant oral self-administration. Alcohol-preferring (P) rats were allowed to lever press concurrently self-administer ethanol (15% vol/vol) and SACC (0.0125% g/vol) for 8 weeks. Rats were then maintained on daily operant access (nondeprived), deprived of both fluids (2 weeks), deprived of SACC and given 2 ml of ethanol daily, or deprived of ethanol and given 2 ml of SACC daily. All groups were then given 2 weeks of daily operant access to ethanol and SACC, followed by an identical second deprivation period. P rats responded more for ethanol than SACC. All deprived groups increased responding on the ethanol lever, but not on the SACC lever. Daily consumption of 2 ml ethanol decreased the duration of the alcohol deprivation effect (ADE). Home cage access to 2 ml of SACC also decreased the ADE but to a lesser extent than access to ethanol. A second deprivation period further increased and prolonged the expression of an ADE. These results show ethanol is a more salient reinforcer than SACC. With concurrent access to ethanol and SACC, P rats do not display a saccharin deprivation effect. Depriving P rats of both ethanol and SACC had the most pronounced effect on the magnitude and duration of the ADE, suggesting that there may be some interactions between ethanol and SACC in their CNS reinforcing effects.

Warsaw high-preferring (WHP) and Warsaw low-preferring (WLP) lines of rats selectively bred for high and low voluntary ethanol intake: preliminary phenotypic characterization

The Warsaw High Preferring (WHP) and Warsaw Low Preferring (WLP) lines were bred from Wistar foundation stock to obtain lines of rats that differ in their preference for ethanol solutions. The WHP line has met several major criteria for an animal model of alcoholism. The WHP rats voluntarily drink excessive amounts of ethanol while the WLP rats consume negligible amounts of ethanol. The WHP rats attain physiologically active blood ethanol concentrations with chronic free-choice drinking. They also develop subtle but visible signs of physical dependence (the withdrawal signs). The patterns of ethanol consumption in WHP and WLP lines are stable in time and independent of the manner of access to ethanol solutions. Notably, when exposed to the increasing ethanol concentrations WHP rats gradually increased total ethanol intake whereas the WLP rats consumed invariably very low amounts of ethanol. Furthermore, the WHP rats show an increased responsiveness to the stimulatory effects of low dose of ethanol.

Phenotypic characterization of genetically selected Sardinian alcohol-preferring (sP) and -non-preferring (sNP) rats

Sardinian alcohol-preferring (sP) and -non-preferring (sNP) rats are one of the pairs of rat lines selectively bred for high and low alcohol preference and consumption, respectively, under the homecage, continuous two-bottle choice regimen. sP rats meet most of the fundamental criteria for an animal model of alcoholism, in that they voluntarily consume sufficient amounts of alcohol to achieve significant blood alcohol levels and produce psychopharmacological effects, including anxiolysis and motor stimulation. sP rats are also willing to 'work' (such as lever-pressing) for alcohol. Chronic alcohol drinking in sP rats results in the development of tolerance to a given effect of alcohol (specifically, motor incoordination) and relapse-like drinking (the alcohol deprivation effect). Conversely, sNP rats avoid alcohol virtually completely; their avoidance for alcohol being resistant even to an environmental manipulation such as long-term exposure to alcohol plus sucrose. sP and sNP rats have been characterized for different phenotypes, possibly associated to their different alcohol preference and consumption. In comparison with sNP rats, alcohol-naive sP rats displayed (1) more anxiety-related behaviors; (2) higher initial sensitivity to the locomotor stimulating and sedative/hypnotic effects of alcohol; and (3) lower sensitivity to the aversive effects of alcohol. The present paper reviews the data collected to date on alcohol drinking behavior and other alcohol-related behaviors in sP and sNP rats. The behavioral profile of sP rats is also compared with that of other lines of selectively bred alcohol-preferring rats and the heterogeneity resulting from this comparison is discussed in terms of different animal models for the different forms of alcoholism.

Suppression of maintenance of alcohol-drinking behavior by the concurrent availability of saccharin in Sardinian alcohol-preferring (sP) rats

In the current study, we investigated the effect of the concurrent presentation of saccharin on the maintenance of alcohol-drinking behavior in selectively bred Sardinian alcohol-preferring (sP) rats. Rats were initially given access to alcohol [10% (volume/volume) in water] and water under the home cage, two-bottle, free-choice regimen, with unlimited access for 24 h/day for eight consecutive weeks. Next, a third bottle, containing saccharin [0%, 0.01%, 0.1%, 1%, or 3% (weight/volume) in water], was concomitantly offered for an additional 10 consecutive days. Intake of saccharin solution resulted as an inverted-U function of saccharin concentration, with the 0.1% saccharin solution being the highest accepted. Alcohol intake was a U function of saccharin concentration, being reduced by 65%-95% in the group of rats exposed to the 0.1% saccharin solution. These results indicate that (1) the concurrent presentation of highly palatable solutions of saccharin markedly reduced alcohol intake in alcohol-experienced sP rats and (2) the reducing effect of saccharin solutions on the alcohol intake in sP rats was positively related to their degree of acceptability. We hypothesized that saccharin solutions may have functioned as a reinforcer, partially substituting for alcohol reinforcement and rendering alcohol drinking less urgent.

Suppression of acquisition of alcohol-drinking behavior by the concurrent availability of saccharin in Sardinian alcohol-preferring (sP) rats

In the current study, we investigated the effect of the concurrent presentation of saccharin on the acquisition of alcohol-drinking behavior in selectively bred Sardinian alcohol-preferring (sP) rats. Alcohol-naive rats were given access to saccharin [0%, 0.01%, 0.1%, 1%, or 3% (weight/volume) in water], alcohol [10% (volume/volume) in water], and water under the home cage, three-bottle, free-choice regimen, with unlimited access for 24 h/day for 10 consecutive days. Intake of saccharin solution resulted as an inverted-U function of saccharin concentration, reaching polydipsic-like values at the 0.1% concentration. In contrast, alcohol intake was a U function of saccharin concentration, being virtually suppressed in the groups of rats exposed to the highly accepted 0.1% and 1% concentrations of saccharin. These results indicate that (1) the concurrent presentation of highly palatable solutions of saccharin suppresses acquisition of alcohol-drinking behavior in sP rats and (2) the suppressive effect of saccharin solutions on the acquisition of alcohol-drinking behavior in sP rats was positively related to their degree of acceptability. We hypothesize that an immediate and continuous access to the highly palatable saccharin solution may have distracted the rat, preventing it from consuming the amounts of alcohol solution needed to disclose and experience the psychopharmacologic effects of alcohol on which alcohol-drinking behavior in sP rats is based.

The High-Ethanol Preferring rat as a model to study the shift between alcohol abuse and dependence

The High-Ethanol Preferring line of rats (HEP), recently selected by R.D. Myers, is characterised by a high voluntary consumption of alcohol (3-4 g/kg/day for males and 6-8 g/kg/day for females, when a 10% ethanol solution is available as a choice vs. water) and a high sensitivity to taste reinforcement (saccharin, quinine). Our previous data obtained with HEP rats showed no evidence of development of dependence after long-term sustained alcohol intake. In this study, we subjected these rats to several long-term administration protocols suggested to favour the development of alcohol dependence, including multiple alcohol concentrations or sweetened alcohol solutions (ethanol 10% or 20%+saccharin), and deprivation periods. The results showed no increase in alcohol consumption, no shift of preference for alcohol solutions when offered as a free choice vs. a preferred saccharin solution, and a very limited alcohol-deprivation effect when alcohol is made available after a period of deprivation, the three criteria used to demonstrate the development of dependence. Regardless of the method used, HEP rats failed to show dependence after long-term, heavy ethanol consumption. Resistance to ethanol dependence may in fact be genetically influenced and the HEP rat appears as a valuable model to search for factors involved in the transition from alcohol abuse to dependence.

Ethanol-conditioned flavor preferences compared with sugar- and fat-conditioned preferences in rats

Rats can learn to prefer flavors paired with ethanol and various nutrients. The present study examined the relative strengths of flavor preferences conditioned by 5% ethanol and isocaloric solutions of 7.18% sucrose, 7.18% fructose, or 3.26% corn oil. In three experiments, nondeprived rats were trained with different flavored solutions (conditioned stimuli, CS) paired with intragastric (IG) infusions: a CS+E flavor paired with ethanol infusion, a second CS+ paired with a nutrient infusion, and a CS- paired with water infusion. In two-bottle tests, rats strongly preferred a sucrose-paired CS+S over the CS- and over the CS+E. The preference for the CS+E over CS- was weaker. These effects occurred when the rats drank substantially more CS+S than CS+E in training and when training intakes were matched. Similar results were obtained when the nutrient infusion was fructose or corn oil, except that preferences for the CS+F or CS+O over the CS+E were less pronounced than with CS+S. Consistent with the IG results, rats trained to drink flavored sucrose and ethanol solutions preferred the CS+S to CS+E in a flavored water test. These results confirm prior reports of ethanol-conditioned preferences but show that ethanol is less effective than other nutrients at isocaloric concentrations. The marked individual differences in ethanol-conditioned preferences may be related to the impact of the sugar or fat infusions on the reward evaluation of the ethanol-paired flavor.

Alcohol addiction research: from animal models to clinics

Addictive behaviour evolves only on the basis of voluntary drug intake. As a consequence, when designing an animal model that covers several aspects of alcohol dependence and other alcohol related-diseases a necessary precondition is that the animal has voluntary access to alcohol. Animal models on voluntary alcohol consumption have a long-standing tradition in biomedical research on alcoholism. However, preference studies allow only limited conclusions regarding alcohol dependence and addictive behaviour. Therefore, new animal models have been developed that mimic different aspects of human alcohol dependence such as craving, relapse and loss of control over drinking. These models include the reinstatement model, the alcohol deprivation model and the point-of-no-return model. These models have now been pharmacologically validated using anti-craving compounds that are used clinically for treating alcoholics. In conclusion, there appears to be a good correspondence between the events that induce relapse and loss of control over alcohol-taking behaviour in laboratory animals and those that provoke relapse and loss of control in humans.

Differential effects of saccharin supplementation on alcohol and water consumption by Wistar rats from different sources

The study was aimed to elucidate whether the dissimilar effects of concurrent presentation of sweet water on alcohol consumption previously reported for Wistar rats from different sources remain unchanged when alcohol is also flavored with 0.1% saccharin. Male Wistar rats from Laboratory of Experimental Biological Models (LEBM) and Krukovo animal farm (K) stocks having had 2 months free access to food, tap water, and 10% alcohol were given four consecutive two-bottle drinking tests: alcohol versus water, alcohol versus sweet water, sweet alcohol versus water, or sweet alcohol versus sweet water. The test order was quasi-random and each test lasted 4 days. In Wistar (K) rats, flavoring of either water or alcohol solution increased consumption of each of the fluids and decreased intake of concurrently available fluids. The elevation in water intake induced by its sweetening was antagonized by flavoring of alcohol solution. In Wistar (LEBM) rats, flavoring of either water or alcohol increased consumption of each of the fluid, but did not change the intake of alternative fluids. The stable alcohol consumption by Wistar (LEBM) rats and its suppression seen in Wistar (K) rats induced by concurrent presentation of flavored water parallel the patterns previously observed among P, sP, and HAD rats suggesting the existence among alcohol-consuming animals of typological diversity of alcohol motivation.

Ethanol intake increases galanin mRNA in the hypothalamus and withdrawal decreases it

Alcoholism can be viewed as a motivational disorder that results from alterations in brain systems for ingestive behavior. Therefore, it was hypothesized that alcohol intake might alter the expression of hypothalamic peptides that stimulate feeding. Earlier studies showed that hypothalamic injection of the feeding-stimulatory peptide, galanin (GAL), increases the release of dopamine (DA) in the nucleus accumbens (NAc), as does systemic alcohol, leading to a focus on GAL. Results of this study demonstrate the following: (1). Ethanol, injected daily (0.8 g/kg 10% v/v) for 7 days in male rats, markedly increased the expression of GAL but not of neuropeptide Y (NPY). This occurred in specific hypothalamic nuclei, namely the dorsomedial nucleus (DMN), paraventricular nucleus (PVN) and perifornical lateral hypothalamus (PLH). (2). Rats induced to drink ethanol ad libitum, by gradually increasing the concentration from 1% to 9% v/v without adding sugar or flavoring, exhibited a similar stimulation of GAL mRNA in the PVN and GAL immunoreactivity in the DMN and PVN. (3). Rats given increasing ethanol concentrations, with 12 h access starting 4 h into the dark cycle, had a mean blood alcohol concentration of 18 mg/dl and exhibited a similar increase in GAL expression in the DMN and PVN. (4) Withdrawal from the opioid effects of 9% ethanol, produced by injection of naloxone (3 mg/kg sc), reversed this ethanol effect by significantly reducing GAL expression in the DMN and PLH below baseline levels. These studies suggest a possible role for hypothalamic GAL in alcohol abuse.

Cholecystokinin reduces ethanol consumption in golden hamsters

In experimental conditions, golden hamsters (Mesocricetus auratus) avidly consume ethanol solutions. However, they are relatively resistant to the deleterious effects of ethanol even after months of continuous consumption, apparently because they metabolize ethanol rapidly and efficiently. Male hamsters with ad libitum access to food and water were presented with isocaloric solutions [weight/weight (wt./wt.)] of 10% ethanol and 17.75% glucose for 40-min periods on alternate days. When hamsters were injected with 0.9% saline before solution presentation the mean intake of ethanol solution (0.55 g) was about half that of glucose solution (1.08 g). Hamsters derived a mean of 0.36 g/kg/40 min of absolute ethanol from the ethanol solution, an amount that does not seem to exceed their metabolic capacity for ethanol. An intraperitoneal injection of a 2.0-microg/kg dose of the C-terminal octapeptide of cholecystokinin (CCK-8) reduced intakes of both solutions by >50% if administered 5 min before solution presentation, but it was ineffectual if administered 45 min before presentation. When citric acid (2.5 g/l) was added to the glucose solution the baseline intakes of the two solutions were virtually equivalent, and when CCK-8 was administered over a range of doses (0.5-2.0 microg/kg) the intakes of the solutions did not differ significantly at any dose, supporting the suggestion that the pharmacological properties of ethanol play little or no role in mediating the consumption-inhibiting effect of exogenously administered cholecystokinin (CCK). Prior administration of lorglumide, a selective CCK type A receptor antagonist, completely attenuated the inhibitory effect of CCK-8. Findings are consistent with the notion that endogenous CCK plays a key role in the short-term control of ethanol intake in hamsters.

Stable preference for high ethanol concentrations after ethanol deprivation in Sardinian alcohol-preferring (sP) rats

Results of a recent study have demonstrated that exposure to multiple ethanol concentrations and repeated ethanol deprivation periods in Indiana ethanol-preferring (P) rats resulted in the development of an alcohol deprivation effect (ADE; the temporary increase in voluntary ethanol intake after a period of deprivation from ethanol) characterized by consumption of intoxicating amounts of ethanol. The current study was designed to possibly extend these results to Sardinian alcohol-preferring (sP) rats, generated with the same selective program previously used for P rats. To this aim, ethanol-naive sP rats were exposed initially to the home cage four-bottle choice [10%, 20%, and 30% (vol./vol.) ethanol solutions and water] for eight consecutive weeks. Subsequently, rats were divided into two groups: The first group had continuous access to the four-bottle regimen (nondeprived rats), and the second group was exposed to five cycles of 14-day periods of deprivation from ethanol and 14-day periods of reexposure to the four-bottle regimen. An ADE developed after each deprivation period. However, the extra intake of ethanol was limited to the first hour of each reaccess period. Magnitude of ADE did not change with repeated periods of deprivation. However, a shift in preference toward the two highest concentrations of ethanol solutions was evident from the first reexposure to ethanol and was maintained throughout the study. These results provide further evidence on the heterogeneity of ethanol-drinking behavior among rat lines selectively bred for high ethanol preference and consumption.

A relation between maze performance and increased ethanol intake in Long-Evans rats

In addition to the neurochemical and genetic basis of high ethanol consumption, there has been renewed interest in studying the role of behavioral variables and their relation to ethanol consumption. The present study was designed to assess whether a relation exists between a behavioral variable such as maze learning ability and ethanol consumption. Sixty, male, Long-Evans rats, exposed to food and water ad libitum, were given a daily trial in a complex, 16-arm T-maze for 19 consecutive days. The number of errors and time to complete the maze were monitored. Individual maze variable scores were transformed and then combined to allot each animal with an index of overall maze performance, with a smaller maze index score denoting good performance. After completion of maze testing, animals were given alternate-day, free-choice presentations of water and ascending doses of ethanol solutions (2%-10%), followed by a 10-day maintenance period with 10% ethanol. Animals were subsequently separated into two groups of high and low drinkers to examine any relation between differential ethanol intake and maze performance. A significant negative correlation between maze index and ethanol intake for the high drinkers group indicated that a smaller maze index was related to increased ethanol intake. No significant correlation was obtained for the low drinkers group. These results seem to indicate that individual variation in learning ability seems to be related to increased ethanol intake. Thus, innate learning processes may be a relevant trait when one attempts to understand the behaviors related to ethanol intake and preference.

Palatable fluids do not affect alcohol intake and its reduction by serotonergic compounds in alcohol-preferring cAA rats

1-(2,5-Dimethoxy-4-iodophenyl)-2-aminopropane (DOI) decreases alcohol intake by alcohol-preferring cAA rats more selectively than fluoxetine in a two-bottle alcohol vs. water paradigm. We report now that availability of sucrose or saccharin in a 3rd bottle does not affect (1) alcohol intake, supporting further the validity of this model of alcoholism, nor (2) the selectivity profile of the alcohol intake-reducing effects of these compounds. It is hypothesized that reduction of alcohol intake by DOI is not simply due to decreased intake of palatable fluids.

Chocolate: food or drug?

Although addictive behavior is generally associated with drug and alcohol abuse or compulsive sexual activity, chocolate may evoke similar psychopharmacologic and behavioral reactions in susceptible persons. A review of the literature on chocolate cravings indicates that the hedonic appeal of chocolate (fat, sugar, texture, and aroma) is likely to be a predominant factor in such cravings. Other characteristics of chocolate, however, may be equally as important contributors to the phenomena of chocolate cravings. Chocolate may be used by some as a form of self-medication for dietary deficiencies (eg, magnesium) or to balance low levels of neurotransmitters involved in the regulation of mood, food intake, and compulsive behaviors (eg, serotonin and dopamine). Chocolate cravings are often episodic and fluctuate with hormonal changes just before and during the menses, which suggests a hormonal link and confirms the assumed gender-specific nature of chocolate cravings. Chocolate contains several biologically active constituents (methylxanthines, biogenic amines, and cannabinoid-like fatty acids), all of which potentially cause abnormal behaviors and psychological sensations that parallel those of other addictive substances. Most likely, a combination of chocolate's sensory characteristics, nutrient composition, and psychoactive ingredients, compounded with monthly hormonal fluctuations and mood swings among women, will ultimately form the model of chocolate cravings. Dietetics professionals must be aware that chocolate cravings are real. The psychopharmacologic and chemosensory effects of chocolate must be considered when formulating recommendations for overall healthful eating and for treatment of nutritionally related health issues.

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

Long-term ethanol consumption in humans and laboratory animals is associated with morphological and functional alterations of brain structures involved in cognitive processes. In the present experiments, we assessed whether voluntary long-term consumption of ethanol by alcohol-preferring (sP) rats under free choice condition with water (also) caused alterations in memory performance and hippocampal acetylcholine (ACh) release in vivo. A group of sP rats were offered a 10% v/v ethanol solution in a free choice with water for 36 weeks; controls had only tap water available. After withdrawal of ethanol, rats were tested in one trial passive avoidance test and thereafter were trained in a food-reinforced radial arm maze task for 12 days. One day after the last session in the radial-arm maze, rats were implanted with a microdialysis probe in the dorsal hippocampus and dialysate concentrations of ACh were measured. No significant differences were observed between sP drinking and control rats in retention latencies in the passive avoidance test, in radial arm-maze performance or in basal levels of hippocampal ACh release. These results show that long-term ethanol consumption by sP rats is not associated with cognitive impairments or with alterations in the hippocampal cholinergic function. To the extent that chronic ethanol intoxication can be considered a causal factor in the development of memory and neurochemical alterations, these results suggest that sP rats self-regulate ethanol consumption so as to avoid intoxication. These findings may challenge the notion that sP rat lines can be considered a valid model of human alcoholism.

Different behavioral patterns related to alcohol use in rodents: a factor analysis

To estimate genetic correlations among behavioral measures from explorative crossmaze, inescapable slip funnel, as well as from drinking tests, the data from five pairs of high/low alcohol drinking rat (AA/ANA, P/NP, HAD1/LAD1, HAD2/LAD2, HIGH-IPH/LOW-IPH) and from three pairs of mouse (B10.AKM/B10.A(4R), HD/LD, Small_Brain/ Large_Brain) lines were evaluated by the use of principal component analysis. The analysis yielded a two-factor solution explaining 71.8% of total variability. Both the factors had high positive loadings on alcohol drinking. The first factor had sufficient positive loadings on latency of crossmaze exploration and total time of slip funnel immobility, whereas, there was a negative loading on slip funnel avoidance. The second factor had positive loadings on efficacy of crossmaze exploration and slip funnel escape attempts, whereas there was a negative loading on slip funnel immobility. The number of defecations in the crossmaze, time in open arms of the elevated plus-maze, time immobile during the forced-swim test, as well as intake of a saccharin solution, additionally available for a lesser number of the lines, were studied for correlations with the factor scores. The first factor of "alcohol drive with timidity and meekness" exhibited positive relation to saccharin intake. Time in the open arms of the elevated plus-maze showed significant negative correlation with a latency of crossmaze exploration. The second factor of "alcohol drive with novelty seeking and persistence" showed a negative link to crossmaze defecations and forced-swim immobility.