Prenatal ethanol exposure causes anxiety-like phenotype and alters synaptic nitric oxide and endocannabinoid signaling in dorsal raphe nucleus of adult male rats

Abstract

Mood disorders, including anxiety and depression caused by prenatal ethanol exposure (PE) are prevalent conditions in fetal alcohol spectrum disorders (FASDs). Prenatal ethanol exposure is associated with persistent dysfunctions of several neurotransmitter systems, including the serotonin (5-HT) system, which plays a major role in mood regulation and stress homeostasis. While PE is known to disrupt the development of the 5-HT system, the cellular mechanisms by which it alters the function of dorsal raphe nucleus (DRn) 5-HT neurons and their synaptic inputs remain unknown. Here, we used a second-trimester binge-drinking pattern PE (two daily gavages of 15% w/v ethanol at 3 g/kg, 5–6 h apart) during gestational days 8 - 20 and measured anxiety-like behaviors of adult male rats using the elevated plus (EPM) and zero (ZM) mazes. We also employed ex-vivo electrophysiological and pharmacological approaches to unravel the mechanisms by which PE alters the excitability and synaptic transmission onto DRn 5-HT neurons. We found that PE enhanced anxiety-like behaviors in adult male rats and induced a persistent activation of DRn 5-HT neurons. The PE-induced activation of DRn 5-HT neurons was largely mediated by potentiation of DRn glutamate synapses, which was caused by activation of the nitrergic system and impaired endocannabinoid signaling. As such, the present study reveals “push-pull” effects of PE on nitrergic and eCB signaling, respectively, which mediate the enhanced activity of DRn 5-HT neurons and could contribute to anxiety-like behaviors observed in animal model of FASD.

Prenatal ethanol exposure leads to persistent anxiety-like behavior during adulthood indicated by reduced horizontal and vertical exploratory behaviors

“…Another study shows no impact of chronic ethanol exposure using ethanol vapor during GDs 5–20 in rats of both sexes using an OF task ( Breit et al, 2022 ). Using the current chronic heavy PE paradigm, we observed increased anxiety-like behavior using elevated plus-maze and zero maze tasks in adult male rats ( Oubraim et al, 2022 ), which is consistent with the current study. The inconsistent observations of anxiety-like behavior after chronic PE could be due to PE paradigms as well as different behavioral tasks used.…”

“…Prenatal ethanol exposure causes lower density of 5-HT neurons ( Druse et al, 1991 ; Ohta et al, 2010 ), fewer 5-HT fibers, impaired 5-HT projections ( Zhou et al, 2001 ), which suggest PE leads to expression of the anxiety-like behavior in animals. A recent study has discovered that PE induced persistent activation of 5-HT neurons and its glutamate synapses by increasing nitrergic function and degrading endocannabinoids signaling in the dorsal raphe 5-HT neurons ( Oubraim et al, 2022 ). This activation exertes the anxiogenic effect, thereby PE animals express anxiety-like behavior.…”

“…Prenatal ethanol exposure in rodents also leads to depressive-like and anxiety-like behaviors ( Hellemans et al, 2010b ). The anxiety-like behavior is shown using various behavioral tasks including elevated plus-maze task ( Osborn et al, 1998 ; Dursun et al, 2006 ; Hwang and Hashimoto-Torii, 2022 ; Oubraim et al, 2022 ) and elevated zero maze task ( Oubraim et al, 2022 ), novelty-induced hypophagia, light–dark box, and open field (OF) ( Rouzer et al, 2017 ). In addition, PE reduces social behaviors in the social interaction task ( Diaz et al, 2016 , 2020 ).…”

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

“…In addition to social deficits, FASD is often associated with the appearance of psychiatric conditions, including anxiety and depression ( Famy et al, 1998 ; Barr, 2006 ; Pei et al, 2011 ). Animal models of prenatal ethanol exposure show anxiety-like behavior in male and female progeny during elevated-plus or O-maze testing ( Dursun et al, 2006 ; Cullen et al, 2013 ; Oubraim et al, 2022 ), with some experiments reporting anxiety-like traits in males only ( Rouzer et al, 2017 ). PEE does not affect elevated plus-maze exploration ( Gibula-Tarlowska et al, 2021 ) but impairs passive avoidance in adult male rats ( Lopatynska-Mazurek et al, 2021b ).…”

Biomarkers of Affective Dysregulation Associated with In Utero Exposure to EtOH

“…Depression and drinking in pregnancy . Depressed women drink more alcohol than nondepressed women [ 24 ], and conversely, PE is a major risk factor for mood disorders [ 25 ]. More than 20% of pregnant women have elevated depressive symptomatology, and 4.7% of pregnant women report treatment with serotonin-specific reuptake inhibitors (SSRIs; [ 26 , 27 , 28 , 29 , 30 , 31 ]).…”