Moderate prenatal alcohol exposure modifies sex-specific CRFR1 activity in the central amygdala and anxiety-like behavior in adolescent offspring

Moderate prenatal alcohol exposure alters GABAergic transmission and the actions of acute alcohol in the medial central amygdala of adolescent rats

Individuals with prenatal alcohol exposure (PAE) are at a higher risk for developing alcohol use disorder (AUD). Using a rat model of moderate PAE (mPAE) on gestational day 12 (G12; ∼2nd trimesters in humans), a critical period for amygdala development, we have shown disruptions in medial central amygdala (CeM) function, an important brain region associated with the development of AUD. In addition to this, acute ethanol (EtOH) increases GABA transmission in the CeM of rodents in a sex-dependent manner, a mechanism that potentially contributes to alcohol misuse. How mPAE alters acute alcohol's effects within the CeM is unknown. Given these findings, we investigated how mPAE may interact with acute alcohol to alter neuronal and synaptic mechanisms in the CeM of adolescent rats in order to understand PAE-induced alcohol-related behaviors. Under basal conditions, mPAE males showed reduced rheobase, indicative of reduced excitability, and females showed a reduction in GABA transmission, indicated by lower spontaneous inhibitory postsynaptic currents (sIPSCs). We found that acute EtOH increased sIPSCs in control males at the middle concentration (66 mM), while mPAE males showed increased sIPSCs only at the highest tested concentration (88 mM). Adolescent females, regardless of PAE status, were largely insensitive to EtOH's effects at all tested concentrations. However, mPAE females showed a significant increase in sIPSCs at the highest tested concentration (88 mM). Overall, these findings support the hypothesis that mPAE leads to sex-specific changes in synaptic activity and neuronal function. Future research is needed to better understand the specific mechanisms by which acute EtOH affects neurotransmission in the adolescent brain of individuals with a history of PAE.

Prenatal ethanol exposure results in cell-type, age, and sex-dependent differences in the neonatal striatum that coincide with early motor deficits

Delayed motor development is an early clinical sign of Fetal Alcohol Spectrum Disorders (FASD). However, changes at the neural circuit level that underlie early motor differences are underexplored. The striatum, the principal input nucleus of the basal ganglia, plays an important role in motor learning in adult animals, and the maturation of the striatal circuit has been associated with the development of early motor behaviors. Here, we briefly exposed pregnant C57BL/6 dams to ethanol (5% w/w) in a liquid diet on embryonic days (E)13.5-16.5, and assessed the mouse progeny using a series of 9 brief motor behavior tasks on postnatal days (P)2-14. Live brain slices were then obtained from behaviorally-tested mice for whole cell-voltage and current clamp electrophysiology to assess GABAergic/glutamatergic synaptic activity, and passive/active properties in two populations of striatal neurons: GABAergic interneurons and spiny striatal projection neurons. Electrophysiologically-recorded spiny striatal projection neurons were also filled intracellularly with biocytin for post-hoc analysis of dendritic morphology. We found that prenatal ethanol exposure resulted in developmental motor delays that were more severe in male mice and coincided with sex-dependent differences in the maturation of striatal neurons. Our findings indicate that prenatal ethanol exposure results in dynamic morphological and functional changes to the developmental trajectories of striatal neurons commensurate with the development of motor behaviors that differ between male and female mice.Significance Statement Developmental differences in motor behaviors are an early clinical sign of Fetal Alcohol Spectrum Disorders (FASD) but the neural circuit level changes that contribute to these differences have not yet been determined. Here we demonstrate that a brief binge exposure to ethanol alters the motor development of neonatal mice in a sex-dependent manner, and identify concurrent differences in the functional, synaptic and morphological development of striatal GABAergic interneurons and medium spiny striatal projection neurons. These data suggest that altered development of striatal neurons may contribute to differences in early motor development observed in individuals with FASD.

The effects of moderate prenatal alcohol exposure on performance in hippocampal-sensitive spatial memory and anxiety tasks by adult male and female rat offspring

Moderate prenatal alcohol exposure (mPAE) results in structural alterations to the hippocampus. Previous studies have reported impairments in hippocampal-sensitive tasks, but have not compared performance between male and female animals. In the present study, performance in hippocampal-sensitive spatial memory and anxiety behavior tests were compared across adult male and female saccharin (SACC) control mPAE Long-Evans rat offspring. Two tests of spatial memory were conducted that were aimed at assessing memory for recently acquired spatial information: A delayed spatial alternation task using an M-shaped maze and a delayed match-to-place task in the Morris water task. In both tasks, rats in SACC and mPAE groups showed similar learning and retention of a spatial location even after a 2-h interval between encoding and retention. A separate group of adult male and female SACC and mPAE rat offspring were tested for anxiety-like behaviors in the elevated plus-maze paradigm. In this test, both male and female mPAE rats exhibited a significantly greater amount of time and a greater number of head dips in the open arms, while locomotion and open arm entries did not differ between groups. The results suggest that mPAE produces a reduction in anxiety-like behaviors in both male and female rats in the elevated plus-maze.

The CRF/Urocortin systems as therapeutic targets for alcohol use disorders

Development and maintenance of alcohol use disorders have been proposed to recruit critical mechanisms involving Corticotropin Releasing Factor and Urocortins (CRF/Ucns). The CRF/Ucns system is comprised of a family of peptides (CRF, Ucn 1, Ucn 2, Ucn 3) which act upon two receptor subtypes, CRFR1 and CRFR2, each with different affinity profiles to the endogenous peptides and differential brain distribution. Activity of CRF/Ucn system is further modulated by CRF binding protein (CRF-BP), which regulates availability of CRF and Ucns to exert their actions. Extensive evidence in preclinical models support the involvement of CRF/Ucn targets in escalated alcohol drinking, as well as point to changes in CRF/Ucn brain function as a result of chronic alcohol exposure and/or withdrawal. It highlights the role of CRF and CRFR1-mediated signaling in conditions of excessive alcohol taking and seeking, including during various stages of withdrawal and relapse to alcohol. Besides its role in the hypothalamic-pituitary-adrenal (HPA) axis, the importance of extra-hypothalamic CRF pathways, especially in the extended amygdala, in the neurobiology of alcohol abuse and dependence is emphasized. Emerging roles for other targets of the CRF/Ucn system, such as CRF2 receptors, CRF-BP and Ucns in escalated alcohol drinking is also discussed. Finally, the limited translational value of CRF/Ucn interventions in stress-related and alcohol use disorders is discussed. So far, CRFR1 antagonists have shown little or no efficacy in human clinical trials, although a range of unexplored conditions and possibilities remain to be explored.

Limbic brain subregions associated with mental health symptoms in youth with and without prenatal alcohol exposure

BACKGROUND

Prenatal alcohol exposure (PAE) can result in reduced brain volume and an increased risk of mental health challenges. Limbic brain structures such as the hippocampus, thalamus, and amygdala often exhibit smaller volumes in youth with PAE, and similar volume reductions are observed in unexposed youth with symptoms of depression, bipolar disorder, anxiety, and schizophrenia. However, the role of volume reductions in these brain regions in mental health challenges remains unclear for individuals with PAE.

METHODS

Thirty-four youth with PAE and 72 unexposed youth aged 7-16 years completed a T1-weighted magnetic resonance imaging scan. FreeSurfer was used to process and extract volumes for hippocampal subfields, thalamic subnuclei, and amygdalar subnuclei. Depression and anxiety symptoms were measured using the Behavioral Assessment System for Children (BASC-2/3-PRS), the Children's Depression Inventory, and the Multidimensional Anxiety Scale for Children. We tested whether limbic subregion volumes differed between youth with and those without PAE and whether volumes were associated with depression and/or anxiety symptoms, controlling for age and gender.

RESULTS

Multiple hippocampal and thalamic subregions, but not amygdalar subnuclei, were smaller in individuals with PAE. Multiple group-brain interactions were observed for depression symptoms and subregion volumes. Negative associations between anxiety and limbic subregions were observed across groups.

CONCLUSIONS

These findings show extensive volume reductions in the hippocampus and thalamus in youth with PAE. PAE also appears to disrupt the association between depression symptoms and limbic subregions in youth, which may have implications for interventions in these individuals. Anxiety symptoms in youth with and without PAE are similarly associated with limbic volumes.

The interaction of genetic sex and prenatal alcohol exposure on health across the lifespan

Prenatal alcohol exposure (PAE) can reprogram the development of cells and tissues, resulting in a spectrum of physical and neurobehavioral teratology. PAE immediately impacts fetal growth, but its effects carry forward post-parturition, into adolescence and adulthood, and can result in a cluster of disabilities, collectively termed Fetal Alcohol Spectrum Disorders. Emerging preclinical and clinical research investigating neurological and behavioral outcomes in exposed offspring point to genetic sex as an important modifier of the effects of PAE. In this review, we discuss the literature on sex differences following PAE, with studies spanning the fetal period through adulthood, and highlight gaps in research where sex differences are likely, but currently under-investigated. Understanding how sex and PAE interact to affect offspring health outcomes across the lifespan is critical for identifying the full complement of PAE-associated secondary conditions, and for refining targeted interventions to improve the quality of life for individuals with PAE.

Combined exposure to alcohol and cannabis during development: Mechanisms and outcomes

Exposure to substances of abuse during pregnancy can have long-lasting effects on offspring. Alcohol is one of the most widely used substances of abuse that leads to the most severe consequences. Recent studies in the United States, Canada, and the United Kingdom showed that between 1% and 7% of all children exhibit signs and symptoms of fetal alcohol spectrum disorder (FASD). Despite preventive campaigns, the rate of children with FASD has not decreased during recent decades. Alcohol consumption often accompanies exposure to such drugs as tobacco, cocaine, opioids, and cannabis. These interactions can be synergistic and exacerbate the deleterious consequences of developmental alcohol exposure. The present review focuses on interactions between alcohol and cannabis exposure and the potential consequences of these interactions.

Postnatal ethanol exposure impairs social behavior and operant extinction in the adult female mouse offspring

Fetal Alcohol Spectrum Disorder (FASD) comprises a group of neurodevelopmental deficits caused by alcohol exposure during pregnancy. Clinical studies suggest that while the male progeny experiences serious neurodevelopmental defects, female patients have more severe cognitive, social, and affective symptoms. Other than sex, dose, frequency, and timing of exposure determine the neurobehavioral outcomes in young and adult progeny. In this regard, human studies indicate that some individuals relapse during late-term gestational periods. In mice, this interval corresponds to the first 10 days after birth (postnatal, P0-P10). In our model of postnatal ethanol exposure (PEE^P0-P10), we tested whether adult female and male offspring show deficits in sociability, anxiety-like, reward consumption, and action-outcome associations. We report that female PEE^P0-P10 offspring have mild social impairments and altered extinction of operant responding in the absence of anxiety-like traits and reward consumption defects. None of these deficits were detected in the male PEE^P0-P10 offspring. Our data provide novel information on sex-specific neurobehavioral outcomes of postnatal ethanol exposure in female adult offspring.