Long term reduction of male agonistic behavior in mice following early exposure to ethanol

The novelty-seeking phenotype modulates the long-lasting effects of intermittent ethanol administration during adolescence

The aim of the present study was to investigate if a novelty-seeking phenotype mediates the long-lasting consequences of intermittent EtOH intoxication during adolescence. The hole board test was employed to classify adolescent mice as High- or Low-Novelty Seekers. Subsequently, animals were administered ethanol (1.25 or 2.5 g/kg) on two consecutive days at 48-h intervals over a 14-day period. Anxiety levels--measured using the elevated plus maze- spontaneous motor activity and social interaction test were studied 3 weeks later. A different set of mice underwent the same procedure, but received only the 2.5 g/kg dose of ethanol. Three weeks later, in order to induce CPP, the same animals were administered 1 or 6 mg/kg of cocaine or 1 or 2.5 mg/kg MDMA. The results revealed a decrease in aggressive behaviors and an anxiolytic profile in HNS mice and longer latency to explore the novel object by LNS mice. Ethanol exposure enhanced the reinforcing effects of cocaine and MDMA in both groups when CPP was induced with a sub-threshold dose of the drugs. The extinguished cocaine-induced CPP (1 and 6 mg/kg) was reinstated after a priming dose in HNS animals only. Our results confirm that intermittent EtOH administration during adolescence induces long-lasting effects that are manifested in adult life, and that there is an association between these effects and the novelty-seeking phenotype.

No effect of prenatal alcohol exposure on activity in three inbred strains of mice

AIMS

Prenatal exposure to alcohol can have adverse effects on the developing fetus. Two of the hallmarks of children exposed to alcohol prenatally are attention deficits and hyperactivity. While hyperactivity has been observed in rats following prenatal ethanol exposure, few studies have examined these effects in mice. The present study investigated the effects of prenatal ethanol exposure on activity in mice from three inbred strains: C57BL/6 (B6), Inbred Long Sleep (ILS) and Inbred Short Sleep (ISS).

METHODS

On Days 7 through 18 of gestation, mice were intragastrically intubated twice daily with either 3.0 g/kg ethanol (E) or an isocaloric amount of maltose-dextrin (MD); non-intubated control (NIC) litters were also generated. Offspring activity was monitored at 30, 60, 90 and 150 days of age.

RESULTS

While results showed no effects of prenatal ethanol exposure on any measures of activity, we did observe differences in baseline activity among the strains. ISS mice were more active than B6 and ILS for all activity measures except stereotypy; B6 mice had higher measures of stereotypy than ILS and ISS. Younger mice were more active than older mice. The only sex effects were on measures of stereotypy, where males had higher scores.

CONCLUSIONS

Mice are an excellent organism to study genetic influences on many phenotypes. However, our study and others have shown few effects of prenatal ethanol exposure on behavior in mice. It appears as if the prenatal period in mice, corresponding to organogenesis, is not a sensitive period for producing behavioral deficits following ethanol exposure. It is likely that the first 2 weeks postnatally, corresponding to the brain growth spurt, are more sensitive for producing behavioral effects.

The effects of neonatal ethanol and/or cocaine exposure on isolation-induced ultrasonic vocalizations

Isolation-induced ultrasonic vocalizations (USVs) are emitted by young rat pups when isolated from their dam and conspecifics. These USVs play an important role in maternal/offspring interactions, and have been used as an indicator of response to stress and isolation. This study examined the effects of neonatal ethanol and/or cocaine exposure on USVs in neonatal rats. The neonatal exposure paradigm serves as a model for the "human third trimester of pregnancy" in terms of CNS development. There were five treatment groups including an artificially reared (AR) ethanol-exposed group (6 g/kg/day), an AR cocaine-exposed group (60 mg/kg/day), an AR ethanol- and cocaine-exposed group (6 g/kg/day+60 mg/kg/day), an AR isocaloric control, and a normally reared control. Both groups that received ethanol took longer to vocalize, and displayed fewer vocalizations than non-ethanol-exposed pups when tested on clean bedding (Experiment 1) or on chips from the nest of a lactating dam (Experiment 2). These results suggest that neonatal ethanol exposure alters the pup's immediate response to isolation. This could have direct effects on maternal/infant interactions, and might help explain some of the long-term effects of ethanol exposure on social behaviors.

Teratogenic actions of ethanol in the mouse: a minireview

The deleterious effects of prenatal ethanol exposure have been extensively documented in clinical and experimental studies. This paper provides an overview of work conducted with mice to examine the myriad of adverse consequences that result from embryonic/fetal exposure to ethanol. All of the hallmark features of the clinical fetal alcohol syndrome have been demonstrated in mice, including prenatal and postnatal growth retardation, structural malformations and behavioral abnormalities associated with central nervous system dysfunction. As expected, the severity and profile of effects is related to both dosage level and timing of exposure. In addition, these effects have been demonstrated following acute and chronic exposure, with a variety of routes of administration employed. Furthermore, a number of strains have been used in these studies and the variant response (susceptibility) to the teratogenic actions of ethanol exhibited among different mouse strains support the notion that genetic factors govern, at least in part, vulnerability to these effects of ethanol. More recent studies using mouse models have focused on examining potential mechanisms underlying the full spectrum of ethanol's teratogenic actions.

Fetal alcohol effects in long- and short-sleep mice: activity, passive avoidance, and in utero ethanol levels

Genetic differences in susceptibility to fetal alcohol effects (FAE) have been suggested by both human and animal studies. The Long-Sleep (LS) and Short-Sleep (SS) mouse lines, selectively bred for differences in ethanol-induced narcosis, provide a model for studying differential alcohol sensitivity in the etiology of FAE. LS and SS mice were intubated with either 2.9 g/kg (20% w/v) ethanol (E) or an isocaloric amount of sucrose (S) twice per day (6 hr apart) on Days 7 through 15 of pregnancy. An untreated control group (C) was maintained for each line. Offspring were fostered to lactating Rockland-Swiss mice at birth. LS offspring prenatally exposed to ethanol exhibited increased open-field activity relative to LS controls, but this effect was due to the overactivity of one litter. Activity for SS mice prenatally exposed to ethanol did not differ from control levels. Ethanol content in blood (280 mg/dl), amniotic fluid (258 mg/dl), and fetal tissue (230 mg/dl) did not differ in similarly treated LS and SS dams. In a second experiment, females were treated from Days 7 through 18 of gestation, and their offspring were tested for either open-field activity or passive avoidance learning. There were no group differences in open-field activity, but LS mice prenatally exposed to alcohol took more trials to reach a passive avoidance criterion than their controls, whereas similarly treated SS mice did not differ from controls. These results suggest that genetically-mediated sensitivity to ethanol influences susceptibility to FAE and that this may be task specific.

Prenatal ethanol exposure fails to affect stimulus reactivity in the rat

Three groups of male Long-Evans rats, that were the offspring of dams maintained throughout pregnancy on a liquid diet in which 35% of the calories were derived from ethanol, pair fed an isocaloric liquid diet that had maltose-dextrin substituted for the ethanol, or maintained on lab chow and water were used as subjects. All subjects were nursed by foster mothers maintained on lab chow and water throughout pregnancy and lactation. The groups were not found to differ on open field activity or number of approaches to four stimulus objects in an open field at 26-30 days of age, on spontaneous alternation at 50-55 days of age or on response to a novel alley at 55 days of age. It was concluded that in the rat, prenatal ethanol exposure does not result in demonstrable changes in responsivity to stimuli in rats tested after 26 days of age.

The effects of ethanol exposure during the brain growth spurt in rats

The purpose of this study was to determine whether micromorphological changes occur at a low level of ethanol exposure previously shown by us to induce alterations in synaptosomal biochemistry. The results suggest that 4 g ethanol per kg body weight daily throughout the brain growth spurt causes no significant structural changes in the cerebellum, lobule IX, at the light and electron microscopic levels. Although ethanol- and isocaloric sucrose-treated groups did not differ from each other in cumulative percent body weight gain throughout the treatment period, both groups differed significantly in this parameter from isocaloric milk-treated and "handled" control groups. On the day following completion of the treatment period, brain weight in the ethanol-treated group was significantly less than that of all other groups. Further, the results indicate that isocaloric sucrose "pair feeding" is contraindicated in postnatal studies and that nutritional status is better controlled by daily gavage of neonates than by other methods currently used in ethanol studies in postnatal animals.

Social models of drinking behavior in animals. The importance of individual differences

Although certain social environments clearly facilitate alcohol intake in humans, the role of social factors in alcohol consumption by animals is less clear. While social housing conditions such as crowding and isolation increase alcohol consumption in animals, in both cases this is mediated by heightened stress. Increases in social tension increase alcohol consumption in social groups of animals, but the literature is extremely variable in reports of how dominance correlates with alcohol consumption. Alcohol administration has biphasic effects on social behavior of animals similar to its biphasic effects on activity levels. We report a novel, social animal model of alcoholism. Rats raised over prolonged periods in highly enriched, social colony environments develop a variety of rhythms of alcohol consumption. But in each colony, only a few animals develop into extreme overconsumers of alcohol, and the proportion of colony-housed animals that develop such excessive alcohol -consumption habits is similar to the proportion of humans with alcohol problems. These overconsumers of alcohol from a rat colony show a variety of alterations in behavior, including chronic inactivity and low dominance standing. They represent a novel, voluntary animal model of social alcoholism.

Effects of prenatal ethanol exposure on avoidance conditioning in high- and low-avoidance rat strains

Two lines of rats selected for high- and low-avoidance performance consumed a nutritious liquid diet containing 35% ethanol-derived calories through days 5--18 of gestation. Control dams were pair-fed an identical liquid diet except for isocaloric substitution of sucrose for ethanol or ad libitum laboratory chow and water. Subsequently, the offspring of the low-avoider dams fed ethanol were found to be impaired ona two-way shock-avoidance conditioning when compared to the pair-fed and ad libitum controls from the same line. In contrast, the offspring of the high-avoider dams fed ethanol displayed similar levels of avoidance, responding to their controls. These results demonstrate that the effects on avoidance conditioning of in utero ethanol exposure are dependent upon the line of rat studied.

Endocrine effects of meternal alcoholization: plasma and brain testosterone, dihydrotestosterone, estradiol, and corticosterone

Maternal ethanol consumption was associated with reduced levels of dihydrotestosterone in the brains of 1--2-day-old male rats when compared to those of sex-matched pups obtained from dames that were fed sucrose. In contrast, brain levels of corticosterone were increased significantly in the pups of ethanol-fed animals when compared to those from sucrose-fed controls. Brain and plasma estradiol did not differ between groups. These results suggest that maternal ethanol consumption may influence the central nervous system and plasma levels of certain steroidal hormones in the offspring.

Effects of ethyl alcohol on behaviour in nursing female mice

Effects of administering 10% ethyl alcohol as drinking fluid to mice during pregnancy and lactation have been examined by ethological analysis of behaviour of nursing females in their home cages at 1 day, 5--7 days, and 12--14 days postpartum. The treatment with alcohol did not affect gestation period or litter size, and fluid intake of treated mice remained similar to that of controls, the average intake of alcohol amounting to 29 mg/g body weight during lactation. Increase in frequency of exploration at 1 day postpartum was the only significant behavioural effect of alcohol on the nursing female mice. Duration of Non-Social Behaviour was unaltered, and no effects of the treatment on Maternal Behaviour or on Social and Sexual Investigation of male partners could be demonstrated. Behaviour of nursing females changed with increase in age of their pups. This occurred to a similar extent in treated and control animals. Maternal and Non-Social Behaviours declined in frequency as the pups became older although the time spent in these behaviours remained fairly constant. Social Investigation of the male partner declined both in frequency and duration while females were nursing their pups.

Increased tolerance in mice following prenatal exposure to barbiturate

HS/Ibg (heterogeneous stock) mice dams were fed milled mouse food containing 3 g/kg phenobarbital (PhB) in acid form and water as their only nutritional source from gestation days 9--19. Control females received milled food and water. Blood PhB levels of treated females and fetuses were 40--200 micrograms/ml blood. At the age of 50 days, male offspring were injected with C14 -sodium pentobarbital (PenB) (50 mg/kg). Sleep time and temperature loss were monitored and, in randomly selected individuals, brain PenB levels were determined upon awakening. The experiment was repeated on the same animals for 3 consecutive days. All offspring developed functional (central nervous system) tolerance during the 3 testing days as evidenced by the daily decrease in sleep time while brain levels of PenB upon awakening increased (P less than 0.001). Offspring who received PhB prenatally had generally shorter sleep times, less temperature loss, and higher brain PenB levels upon awakening than controls. The differences were most pronounced on the second day (sleep time reduced 27%, P less than 0.001; temperature loss 47%, P less than 0.001; brain PhB levels increased 23%, P less than 0.01).

Effects of maternal drinking on neonate state regulation

Sleep-awake state distribution during inter-feed intervals over a 24-hour period on the third day of life was investigated by means of a continuous non-intrusive bassinet sleep monitor. 31 infants were studied: 14 born to mothers who drank heavily throughout pregnancy (group A), eight whose mothers modified their heavy drinking (group B) and nine whose mothers never were heavy drinkers (group C). Over the 24-hour period, group A infants slept less than those in group B. In comparison with group C, group A infants had a larger proportion of quiet sleep episodes interrupted by awake or unclassified epochs, and were more restless, with more frequent major body movements. These pilot observations suggest that heavy maternal consumption of alcohol, when continued throughout pregnancy, is associated with a disturbance of sleep-awake state distribution. Successful therapy of heavy drinking during pregnancy may improve the physiological competence of the newborn to regulate sleep-awake states and facilitate interaction between mother and infant.

Effects of ethyl alcohol on development and social behaviour in the offspring of laboratory mice

Behavioural and developmental effects of exposure to a low level of ethyl alcohol from conception to adulthood have been examined in mice. A 5% solution of alcohol in the drinking fluid of male and female adults did not impair fertility. The offspring of treated mice were significantly lighter at birth than their controls and remained so throughout their life span. No congenital malformations were observed. Behaviour of the offspring 3--4 weeks of age and in adulthood was examined by ethological analysis of encounters between alcohol-treated and control mice of the same sex. In male and female juvenile mice receiving 5% alcohol, the frequency and duration of social investigation were significantly lower than those of control partners and the duration of non-social behaviour was raised. Individual elements of 'investigate' and 'sniff' were significantly reduced in frequency. In alcohol-treated adults, the only behavioural difference from controls was an increased frequency of flight elements occurring in males. It is suggested that long-term exposure to alcohol may lead to behavioural adaptation.

Growth and behavioural effects of ethyl alcohol on the offspring of mice; a comparison with its short-term actions

Ten percent ethyl alcohol as drinking fluid of breeding mice did not affect gestation period, litter size or litter weight. Alcohol was secreted in milk, and weight gain up to weaning was reduced in offspring of treated mice, males having significantly reduced weights at 3--4 weeks. When weaned at 21 days, treated offspring were given 10% alcohol to drink. Intake amounted to 31 mg/g body weight each day on average. Ethological analysis of behaviour occurring in encounters between alcohol-treated and control mice of the same sex showed that exploration and scanning were increased in duration in treated mice of both sexes and were increased in frequency in treated females. The frequency of self-grooming was reduced in treated mice of both sexes and scratching in treated males. Ethyl alcohol (10%) as drinking fluid for 5 days to 21 day old mice procuced different behavioural effects. In treated males the social elements, 'investigate', 'sniff' and 'follow' were increased in frequency during encounters and 'digging' was reduced. Treated females showed no change in social behaviour. Weight gain was reduced in treated males.