Deficits in spatial learning and memory in adult mice following acute, low or moderate levels of prenatal ethanol exposure during gastrulation or neurulation.

Debate continues on the merits of strictly limiting alcohol consumption during all of pregnancy, and whether "safe" consumption levels and/or times exist. Only a relatively few experimental studies have been conducted that limit the timing of exposure to specific events during development and the exposure level to one that might model sporadic, incidental drinking during pregnancy. In the present study, the effects of two acute gavage exposures to low and moderate levels of ethanol (peak blood ethanol concentrations (BEC) of 104 and 177mg/dl, respectively) either during gastrulation on gestational day (GD) 7 (at GD7:0h and GD7:4h) or during neurulation on GD8 (at GD8:6h and GD8:10h) on the spatial learning and memory abilities of adult mice in the radial arm maze (RAM) were examined. Mice were selected from a prenatal ethanol exposure (PAE) cohort that had been tested as neonates for their sensorimotor development (Schambra et al., 2015) and as juveniles and young adults for open field activity levels and emotionality (Schambra et al., 2016). Mice exposed on either of the two gestational days to acute, low or moderate levels of ethanol were deficient in overall performance in the RAM in adulthood. Importantly, mice in ethanol exposed groups took longer to reach criterion in the RAM, and many mice in these groups failed to do so after 48 trials when testing was terminated. Exposure to a low level of ethanol on either GD7 or GD8, or a moderate level on GD7, resulted in significant impairment in spatial reference (long-term) memory, while only mice exposed on GD7 to the low level of ethanol were significantly impaired in spatial working (short-term) memory. Mice exposed to the low ethanol level on either day had significantly shorter response latencies, which may reflect impairment of processes related to response inhibition or executive attention in these mice. For all measures, distributions of individual scores revealed a relatively small subset of mice in each PAE group who scored well outside the range of the control group, which skewed the population distributions to varying degrees in the direction of worse performance for the PAE groups. Overall the data suggest that after acute, low level ethanol exposure early in gestation, the likelihood that an individual mouse embryo experienced measureable ill-effects due to the exposure was rather low, but in a few of the embryos, damage occurred that resulted in significant deficits in later performance. The overall characteristics of our cohort of PAE mice, including delayed sensorimotor development, mild hypoactivity and increased emotionality, as shown in previous studies, together with deficits in spatial learning and memory as shown here, resemble those in a subset of human Fetal Alcohol Spectrum Disorder (FASD) diagnoses, specifically ADHD-Inattentive type (ADHD-I) and/or Sluggish Cognitive Tempo (SCT). Although possible correspondences between mechanisms underlying PAE-induced deficits in mice and those operating in humans remain undefined, further study with this mouse PAE model may ultimately help advance understanding of the causes of these conditions in affected children. This study highlights the possibility of risk associated with low to moderate sporadic alcohol consumption during the first month of human pregnancy.

Consequences of low or moderate prenatal ethanol exposures during gastrulation or neurulation for open field activity and emotionality in mice.

In a previous study we used a mouse model for ethanol exposure during gastrulation or neurulation to investigate the effects of modest and occasional human drinking during the 3rd or 4th week of pregnancy (Schambra et al., 2015). Pregnant C57Bl/6J mice were treated by gavage during gastrulation on gestational day (GD) 7 or neurulation on GD8 with 2 doses 4h apart of either 2.4 or 2.9g ethanol/kg body weight, resulting in peak blood ethanol concentrations (BECs) of 104 and 177mg/dl, respectively. We found that mice exposed to the low dose on either day were significantly delayed in their neonatal sensorimotor development. In the present study, we tested the same cohort of mice in an open field as juveniles on postnatal day (PD) 23-25 and as young adults on PD65-67 for prenatal ethanol effects on exploration and emotionality with measures of activity, rearing, grooming and defecation. We evaluated the effects of dose, sex, day of treatment and day of birth by multiple regression analyses. We found that, compared to the respective gavage controls, juvenile mice that had been prenatally exposed to the low BEC on either GD7 or GD8 were significantly hypoactive on the first 2 test days, reared significantly more on the last 2 test days, and groomed and defecated significantly more on all 3 test days. Only mice that had been treated on GD7 remained hypoactive as adults. Juvenile mice prenatally exposed to the moderate BEC on GD7 groomed significantly more, while those exposed on GD8 reared and defecated significantly more. Sex differences were highly significant in adult control mice, with control males less active and more emotional than females. Similar, but smaller, sex differences were also evident in adults exposed to ethanol prenatally. Persistence into later life of a deleterious effect of premature birth (i.e., birth on GD19 rather than GD20) on weight and behavior was not consistently supported by these data. Importantly, mice shown previously to be delayed in sensorimotor development as neonates, in the present study demonstrated hypoactivity and increased emotionality in open field behaviors as juveniles, and those mice exposed during gastrulation remained hypoactive as adults. Thus, we propose that the delayed motor development, hypoactivity and emotionality we observed in mice exposed to a low BEC during gastrulation or neurulation may relate to an attention deficit-activity disorder in humans, possibly the inattentive subtype, or Sluggish Cognitive Tempo (SCT). We further discuss concerns about occasional light or moderate alcohol consumption during the 3rd or 4th week of human pregnancy.

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.

A gene expression atlas of the central nervous system based on bacterial artificial chromosomes.

The mammalian central nervous system (CNS) contains a remarkable array of neural cells, each with a complex pattern of connections that together generate perceptions and higher brain functions. Here we describe a large-scale screen to create an atlas of CNS gene expression at the cellular level, and to provide a library of verified bacterial artificial chromosome (BAC) vectors and transgenic mouse lines that offer experimental access to CNS regions, cell classes and pathways. We illustrate the use of this atlas to derive novel insights into gene function in neural cells, and into principal steps of CNS development. The atlas, library of BAC vectors and BAC transgenic mice generated in this screen provide a rich resource that allows a broad array of investigations not previously available to the neuroscience community.