Viability and sensorimotor development of mice exposed to prenatal short-term ethanol

Low and moderate prenatal ethanol exposures of mice during gastrulation or neurulation delays neurobehavioral development

Human and animal studies show significant delays in neurobehavioral development in offspring after prolonged prenatal exposure to moderate and high ethanol doses resulting in high blood alcohol concentration (BECs). However, none have investigated the effects of lower ethanol doses given acutely during specific developmental time periods. Here, we sought to create a mouse model for modest and circumscribed human drinking during the 3rd and 4th weeks of pregnancy. We acutely treated mice during embryo gastrulation on gestational day (GD) 7 or neurulation on GD8 with a low or moderate ethanol dose given via gavage that resulted in BECs of 107 and 177 mg/dl, respectively. We assessed neonatal physical development (pinnae unfolding, and eye opening); weight gain from postnatal day (PD) 3-65; and neurobehavioral maturation (pivoting, walking, cliff aversion, surface righting, vertical screen grasp, and rope balance) from PD3 to 17. We used a multiple linear regression model to determine the effects of dose, sex, day of treatment and birth in animals dosed during gastrulation or neurulation, relative to their vehicle controls. We found that ethanol exposure during both time points (GD7 and GD8) resulted in some delays of physical development and significant sensorimotor delays of pivoting, walking, and thick rope balance, as well as additional significant delays in cliff aversion and surface righting after GD8 treatment. We also found that treatment with the low ethanol dose more frequently affected neurobehavioral development of the surviving pups than treatment with the moderate ethanol dose, possibly due to a loss of severely affected offspring. Finally, mice born prematurely were delayed in their physical and sensorimotor development. Importantly, we showed that brief exposure to low dose ethanol, if administered during vulnerable periods of neuroanatomical development, results in significant neurobehavioral delays in neonatal mice. We thus expand concerns about alcohol consumption during the 3rd and 4th weeks of human pregnancy to include occasional light to moderate drinking.

Postnatal growth restriction and gene expression changes in a mouse model of fetal alcohol syndrome

Growth restriction, craniofacial dysmorphology, and central nervous system defects are the main diagnostic features of fetal alcohol syndrome. Studies in humans and mice have reported that the growth restriction can be prenatal or postnatal, but the underlying mechanisms remain unknown.We recently described a mouse model of moderate gestational ethanol exposure that produces measurable phenotypes in line with fetal alcohol syndrome (e.g., craniofacial changes and growth restriction in adolescent mice). In this study, we characterize in detail the growth restriction phenotype by measuring body weight at gestational day 16.5, cross-fostering from birth to weaning, and by extending our observations into adulthood. Furthermore, in an attempt to unravel the molecular events contributing to the growth phenotype, we have compared gene expression patterns in the liver and kidney of nonfostered, ethanol-exposed and control mice at postnatal day 28.We find that the ethanol-induced growth phenotype is not detectable prior to birth, but is present at weaning, even in mice that have been cross-fostered to unexposed dams. This finding suggests a postnatal growth restriction phenotype that is not due to deficient postpartum care by dams that drank ethanol, but rather a physiologic result of ethanol exposure in utero. We also find that, despite some catch-up growth after 5 weeks of age, the effect extends into adulthood, which is consistent with longitudinal studies in humans.Genome-wide gene expression analysis revealed interesting ethanol-induced changes in the liver, including genes involved in the metabolism of exogenous and endogenous compounds, iron homeostasis, and lipid metabolism.

A Mouse Model of Prenatal Ethanol Exposure Using a Voluntary Drinking Paradigm

BACKGROUND

The incidence of fetal alcohol spectrum disorders is estimated to be as high as 1 in 100 births. Efforts to better understand the basis of prenatal ethanol-induced impairments in brain functioning, and the mechanisms by which ethanol produces these defects, will rely on the use of animal models of fetal alcohol exposure (FAE).

METHODS

Using a saccharin-sweetened alcohol solution, we developed a free-choice, moderate alcohol access model of prenatal alcohol exposure. Stable drinking of a saccharin solution (0.066%) was established in female mice. Ethanol then was added to the saccharin in increasing concentrations (2%, 5%, 10% w/v) every 2 days. Water was always available, and mice consumed standard pellet chow. Control mice drank saccharin solution without ethanol. After a stable baseline of ethanol consumption (14 g/kg/day) was obtained, females were impregnated. Ethanol consumption continued throughout pregnancy and then was decreased to 0% in a step-wise fashion over a period of 6 days after pups were delivered. Characterization of the model included measurements of maternal drinking patterns, blood alcohol levels, food consumption, litter size, pup weight, pup retrieval times for the dams, and effects of FAE on performance in fear-conditioned learning and novelty exploration.

RESULTS

Maternal food consumption, maternal care, and litter size and number were all found to be similar for the alcohol-exposed and saccharin control animals. FAE did not alter locomotor activity in an open field but did increase the time spent inspecting a novel object introduced into the open field. FAE mice displayed reduced contextual fear when trained using a delay fear conditioning procedure.

CONCLUSIONS

The mouse model should be a useful tool in testing hypotheses about the neural mechanisms underlying the learning deficits present in fetal alcohol spectrum disorders. Moreover, a mouse prenatal ethanol model should increase the opportunity to use the power of genetically defined and genetically altered mouse populations.

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.

Perinatal maternal ethanol effects on pregnant mice and on offspring viability and growth: influences of exposure time and weaning diet

C57BL/6 mice were maintained on liquid diets containing 27.5% ethanol-derived calories beginning on gestational day 12. For one group, the liquid diet was replaced with laboratory chow on the morning of gestational day 18, approximately 24 hr before delivery. For a second group, the diet was continued for 7 days postnatally. Two additional groups were pair-fed isocaloric sucrose diets, and a final group was maintained on normal laboratory chow. The mice consumed sufficient amounts of diet to provide near 30 g ethanol/kg/day during pregnancy and slightly greater amounts during the first postpartum week. The ethanol diet produced no maternal deaths and did not alter weight gain during gestational days 12-17 of pregnancy. The results confirmed previous reports that dietary ethanol exposure under conditions that have rather minor effects on the pregnant mouse can substantially affect the fetus. As previously reported, when exposure was terminated 24 hr before delivery, neonatal mortality was elevated by approximately 30%, but birth weight was not altered. When the diet was extended into the lactation period, mortality was delayed but not reduced, possibly by reducing the severity of ethanol withdrawal. Birthweight was reduced by 10% when exposure continued until birth, suggesting that low birthweights for fetal ethanol-exposed (FEE) mice can be eliminated by terminating exposure approximately 24 hr before delivery. As in previous reports, FEE mice with normal birthweights had an attenuated preadolescent growth spurt, suggesting that low birthweights and attenuated postnatal growth are likely mediated by different mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Postnatal growth deficits in prenatal ethanol-exposed mice: characteristics and critical periods

We previously reported that offspring of C57BL/6 mice maintained on liquid diets containing 20% or 25% ethanol-derived calories throughout pregnancy had birth weights comparable with controls but had weight reductions that became manifest around 23 to 28 days postnatally. Since this pattern of weight reduction may represent an unrecognized condition for human ethanol exposure, we completed a number of experiments to more thoroughly characterize the altered growth of prenatal ethanol exposed C57BL/6 mice. The results of this study indicate that consumption of liquid diets containing either 17% or 25% ethanol-derived calories during pregnancy can reduce growth of male and female offspring. Although attenuated postnatal growth of prenatal ethanol-exposed rodents is not commonly reported, prospective studies in humans suggest that in addition to having lower birth weights, children prenatally exposed to ethanol are postnatally growth retarded. Mice exposed to the low ethanol doses used in the present study had normal birth weights; however, their growth was attenuated between 19 and 28 days of age (preadolescent growth spurt) resulting in a weight reduction for at least 35 days, and which according to our previous report could extend into adulthood. The latter stages of gestation appear to be more sensitive to the postnatal growth retarding effect of prenatal ethanol exposure than early gestation. Caloric deficiency and postnatal maternal factors were eliminated as possible mechanisms for the growth deficit.

Sensorimotor maturation and alcohol responsiveness in rats prenatally exposed to alcohol during gestational day 8

On gestational day 8, pregnant Sprague-Dawley derived rats received two intraperitoneal injections of 0.015 ml/g body weight of a 24% v/v ethanol solution representing an absolute alcohol dose of 2.82 g/kg per administration (ETOH Group). Control females were injected with similar volumes of saline (SAL Group) or did not receive any type of intraperitoneal administration of drugs (AC Group). In comparison with the control treatments, the ethanol treatment did not affect long-term maternal body weight gain during pregnancy, total length of gestation, probability of delivery, number of pups born per litter or the offsprings' preference of alcohol odor. Nevertheless, this ethanol insult was sufficient to significantly reduce body weights at birth and to retard the ontogeny of some sensorimotor patterns among offspring, as assessed through the Righting Reflex, Horizontal Screen Test and opening of the external auditory canals. The maturation of other reflexes (Cliff Aversion and Negative Geotaxis) appeared to be retarded indirectly as an outcome of the maternal injection procedure, with ETOH and SAL pups exhibiting similar developmental delays when compared with AC animals. During adulthood, rats prenatally exposed to alcohol exhibited a decreased hypothermic response to an intoxicating dose of alcohol as well as significant increases in voluntary alcohol consumption in comparison with both control conditions. Collectively, these results suggest that relatively acute alcohol exposure early in gestation may not only affect normal patterns of development but also later responsiveness to this pharmacological agent.

Effects of maternal ethanol consumption on the offspring sensory-motor development, ultrasonic vocalization, audiogenic immobility reaction and brain monoamine synthesis

Female rats were given 16% ethanol solution as the sole liquid during the entire period of gestation. At birth the offspring was removed and reared by foster dams consuming normal tap water. The development of sensory motor behaviour and emotional reactions was delayed by 1-2 days in the prenatally ethanol exposed pups as assessed by tests on body righting, acoustic startle response, air righting, rearing and ultrasonic vocalization. In the open-field test the normally occurring behavioural difference between the sexes was not found in the prenatally ethanol exposed pups. Both sexes of the ethanol exposed pups behaved like the female controls suggesting deficient masculinization of the ethanol exposed male pups during foetal age. Biochemical analysis of the brains showed a decreased synthesis of serotonin and dopamine.