Kim Cronise

Critical periods for the effects of alcohol exposure on brain weight, body weight, activity and investigation.

Using an animal model of fetal alcohol syndrome - which equates peak blood alcohol concentrations across different developmental periods - critical periods for the effect of alcohol on brain weight, activity and investigative behavior were examined. The periods of alcohol exposure were from gestational day (GD) 1 through 10, GD 11 through 22, postnatal day (PD) 2 through 10, or all three periods combined. The critical period of alcohol exposure for an increase in activity in juveniles was GD 11 through 22. This pattern was not seen in the same animals in adulthood; instead, increases in both activity and investigation were seen in animals exposed from PD 2 through 10 and not seen in animals exposed during all three periods combined. Brain weight was reduced by alcohol exposure from GD 11 through 22, PD 2 through 10 and all three periods combined. The period from PD 2 through 10 was the only period when the brain weight to body weight ratio was reduced. In conclusion, exposure to alcohol during the periods in the latter half of gestation or early postnatal period seem to have the most deleterious effects on the brain, activity and investigation in the rat. In addition, the effects of alcohol exposure over both the prenatal and postnatal period cannot be easily predicted from the effects of shorter periods of exposure.

A procedure to produce high alcohol intake in mice

RationaleWhile prolonged access to ethanol (EtOH), or deprivations, or their combination have occasionally been shown to yield high levels of voluntary self-administration, in almost all cases, rodents do not self-administer alcohol to the degree that they will develop substantial, intoxicating blood alcohol levels and then continue to self-administer at these levels.ObjectivesThe purpose of the present series of experiments was to modify a fluid restriction procedure to demonstrate consistent, high EtOH consumption.MethodsMale and female mice from an alcohol preferring inbred strain (C57BL/6J; B6) as well as from a genetically heterogeneous strain (WSC) were given varying periods of access to fluid, ranging from 90 min to 10 h per day, for 12–21 days. Every 3rd or 4th day, separate groups of mice were offered a 5, 7 or 10% EtOH solution for either 10 min or 30 min, followed by water for the remainder of the time.ResultsIn all studies, stable high EtOH doses were consumed by both B6 and WSC mice across the EtOH sessions, exceeding 2 g/kg in a 30-min session. Mean blood EtOH concentration exceeded 1 mg/ml (i.e. 100 mg%), with values in individual animals ranging from 0.6 mg/ml to 3.4 mg/ml. Notably, mice receiving 10 h of fluid/day continued to consume 2 g/kg doses of EtOH. While this procedure did not produce subsequent preference for EtOH in WSC mice, consumption remained high in some animals.ConclusionsThese data indicate that scheduling fluid intake produces high, stable EtOH consumption and BEC in male and female B6 and WSC mice.

Anxiety‐Like Behavior in Mice in Two Apparatuses During Withdrawal From Chronic Ethanol Vapor Inhalation

BACKGROUND Anxiety during ethanol withdrawal may be a factor in relapse to alcohol abuse and dependence. Animal models of ethanol withdrawal have typically used forced consumption of an ethanol-containing liquid diet to induce dependence. Ethanol vapor inhalation offers an advantage over liquid diet consumption in that the onset of withdrawal can be temporally controlled more precisely, allowing studies of the development of withdrawal symptoms. METHODS The purpose of the current study was to induce ethanol dependence in mice using an inhalation procedure and to assess withdrawal anxiety symptoms behaviorally in the elevated zero maze and in the light/dark box. Male and female mice were exposed to 3 days of ethanol vapors. Anxiety-like behavior was measured on the elevated zero maze and light/dark box at multiple time points during withdrawal. RESULTS Mice experiencing ethanol withdrawal demonstrated increased anxiety-like behaviors relative to control animals in both apparatuses. However, this finding was specific to the procedure used with the elevated zero maze and was strongly influenced by sex in the light/dark box. CONCLUSIONS Ethanol vapor inhalation appears to be a valid tool for the study of withdrawal-induced anxiety.

Critical periods for the effects of alcohol exposure on learning in rats.

Critical periods for alcohol-induced deficits in spatial navigation and passive avoidance learning were investigated with a rat model of fetal alcohol syndrome. Rats were exposed to alcohol prenatally (Gestational Days 1-10 or 11-22) or postnatally (Postnatal Days 2-10) or throughout all 3 periods. Offspring were tested in either a spatial navigation or an avoidance task as juveniles or adults. As juveniles, the combined exposure group took longer to learn the spatial navigation task compared with all other groups. This effect was not seen in adults. Passive avoidance performance was not affected. These results suggest that long-term exposure to alcohol during development has adverse effects on spatial learning. The lack of differences in the short-term exposure groups implies that there may not be 1 critical period of alcohol exposure, but that the adverse effects of alcohol during development may be cumulative on some behaviors.

Scheduled access to ethanol results in motor impairment and tolerance in female C57BL/6J mice

We recently reported a method where water-restricted mice were given scheduled access to ethanol followed by access to water. C57BL/6J mice would repeatedly self-administer ethanol in amounts that produced high and stable blood ethanol concentrations (BEC) [Finn DA, Belknap JK, Cronise K, Yoneyama N, Murillo A, Crabbe JC. A procedure to produce high alcohol intake in mice. Psychopharmacol 2005;178:471-480]. The studies reported here demonstrate that behavioral signs of motor impairment result from these high alcohol intakes, and that there was some evidence of tolerance development across repeated sessions. Female C57BL/6J mice were allowed 30 min access to ethanol (5% v/v) followed by 2.5 h access to water either: every 3rd day for 12 days; every 2nd day for 28 days; or every 2nd day for 9 days. On intervening days, mice had 3 h access to water. A control group had daily access to water only. Mice consumed 2-2.5 g/kg ethanol in 30 min, resulting in BECs of 1.4-1.5 mg/ml. Motor impairment was assessed using the accelerating or fixed speed rotarod, balance beam or screen test. In all studies, mice were tested for motor impairment immediately after 30 min access to ethanol or water. In Experiment 1, ethanol-exposed mice had shorter latencies to fall from the fixed speed rotarod and more foot slips on the balance beam than the control group, indicating motor impairment. After drinking ethanol, mice also fell from a screen more quickly than during sober pretraining. In Experiment 2, mice tested (without prior training) for motor impairment and tolerance on the fixed speed rotarod at 6.5 and 10 RPM showed repeated motor impairment in the ethanol group, but did not develop tolerance. In Experiment 3, mice were first given rotarod training at 10 RPM. Following each fluid access period, performance was impaired in mice self-administering ethanol at 10, but not 15 RPM, when compared to control mice. There was no evidence of tolerance across days. However, on the last day, all mice were tested at both RPM following an i.p. injection of 2 g/kg ethanol. Ethanol-experienced mice were less impaired at both RPM than the ethanol-naïve mice, indicating tolerance development according to this between-groups index. These results suggest that C57BL/6J mice will repeatedly consume alcohol in amounts that produce motor impairment under these scheduled fluid access conditions, and that a modest degree of tolerance can be detected using appropriate tests.

Sexually Dimorphic Effects of Alcohol Exposure during Development on the Processing of Social Cues

AIMS The study used an animal model of fetal alcohol spectrum disorders (FASD) to investigate the impact of alcohol exposure during a period equivalent to all three trimesters in humans on social recognition memory. It was hypothesized that the effects on specific aspects of social recognition memory would be sexually dimorphic. METHODS This study exposed rats to ethanol during both the prenatal and early postnatal periods. Two control groups included a group exposed to the administration procedures but not ethanol and a non-treated group. At approximately 90 days, all rats were tested repeatedly in a test of social recognition memory with a juvenile animal of the same sex. Experimental rats of both sexes were allowed to investigate an unknown juvenile for either 2, 3 or 5 min and then, after a delay of 30, 60, 120 and 180 min, were allowed to investigate the same juvenile for 5 min. RESULTS Male rats investigated the juvenile for much longer than female rats. Ethanol-exposed male rats showed a deficit in recognition memory that was evident with longer delays when the initial investigation time was either 2- or 3-min long. In contrast, ethanol-exposed female rats showed a deficit in recognition memory only when the initial investigation period was of 2 min. Measurement of oxytocin receptor binding in the amygdala region indicated that ethanol exposure lowered oxytocin receptor binding in females but not males. CONCLUSIONS The results suggest that ethanol exposure during development caused a deficit in memory duration but not encoding in males and a deficit in encoding but not memory duration in females. The deficit in ethanol-exposed females may be related to changes in oxytocin receptors in the amygdala.

Home cage activity and ingestive behaviors in mice following chronic ethanol vapor inhalation

Although drug withdrawal may induce an anxiety-like state, decreased locomotion in tests of anxiety-like behavior is an almost universal finding in rodent studies of ethanol withdrawal. Decreased locomotion in many behavioral apparatus, either as a result of a withdrawal-induced lethargy, malaise, or reduced motivation to explore confounds interpreting the effects of withdrawal as specifically increasing an anxiety-like state. To address this issue, we measured home cage activity levels as well as food and water intake for 3 days prior to and up to 5 days after chronic ethanol vapor exposure in genetically heterogeneous mice. In the first experiment, ethanol-withdrawing WSC-2 mice drank less water than controls, but did not differ from controls on any other behavioral measure during the withdrawal assessments. When the dose of ethanol was elevated in a subsequent experiment in WSC-2 mice, a similar temporary decrease in food and water intake, but not in locomotion, was observed during withdrawal. These results differed from those of mice placed into activity monitors during peak withdrawal, which exhibited profoundly reduced activity levels compared to controls. Finally, home cage activity levels during withdrawal were only transiently decreased in a mouse line that has been selectively bred to display high ethanol withdrawal handling-induced convulsion severity (WSP mice). The reduction in food and water consumption seen in most experiments suggests that withdrawal may induce a temporary malaise-like state, but this state is not reflected in altered home cage activity levels. Further, even in a relatively severe mouse model of alcohol withdrawal, any decreases in general home cage activity are short-lived.

Maternal urinary tract infection alters water maze performance in the offspring.

The effects of maternal urinary tract infection (UTI) or endotoxin exposure on fetal outcome in rats were investigated. Prior to conception, dams of the UTI group were water-deprived and anesthetized. The urinary tract was then catheterized and injected with 0.2 of 1 x 10(9) Escherichia coli. The endotoxin group was injected with 0.03 mg/kg lipopolysaccharide on the fourth day of gestation and then every third day thereafter. The control groups were treated in the same manner, with the exception that the infection control was not catheterized or injected with E. coli, and the endotoxin control was not exposed to lipopolysaccharide. A nontreated control group was weighed daily. Beginning on postnatal day (PD) 19, offspring were tested daily in a water maze spatial navigation task. The retention latencies (Sessions 7--10) revealed deficits in the infection and endotoxin groups. In the rat model, these findings suggest that exposure during gestation to a maternal immune challenge may result in adverse fetal outcome.

Murine Models of Substance and Alcohol Dependence

Most behavioral traits operate on a phenotypic and genetic continuum, i.e., the phenotypic output is quantitative based on the genetic input. No one gene is either necessary or sufficient to account for the observed phenotype; rather, a collection of genes is responsible. This phenotypic and genetic complexity is particularly evident in psychological disorders. For instance, first-degree relatives of schizophrenics have a 9% risk for a diagnosis, whereas the risk drops to 2% for a third-degree relative (1. These findings suggest that many genes contribute, and as the proportion of shared genes increases among relatives, so does the likelihood of shared diagnosis. Regardless of commonalities among genotypes, phenotypic expression may vary significantly in the frequency and severity of symptoms. This further supports the contention that several genes contribute to the trait, each with small effects.