Prenatal alcohol and tetrahydrocannabinol exposure: Effects on spatial and working memory

Introduction

Alcohol and cannabis are widely used recreational drugs that can negatively impact fetal development, leading to cognitive impairments. However, these drugs may be used simultaneously and the effects of combined exposure during the prenatal period are not well understood. Thus, this study used an animal model to investigate the effects of prenatal exposure to ethanol (EtOH), Δ-9-tetrahydrocannabinol (THC), or the combination on spatial and working memory.

Methods

Pregnant Sprague-Dawley rats were exposed to vaporized ethanol (EtOH; 68 ml/h), THC (100 mg/ml), the combination, or vehicle control during gestational days 5-20. Adolescent male and female offspring were evaluated using the Morris water maze task to assess spatial and working memory.

Results

Prenatal THC exposure impaired spatial learning and memory in female offspring, whereas prenatal EtOH exposure impaired working memory. The combination of THC and EtOH did not exacerbate the effects of either EtOH or THC, although subjects exposed to the combination were less thigmotaxic, which might represent an increase in risk-taking behavior.

Discussion

Our results highlight the differential effects of prenatal exposure to THC and EtOH on cognitive and emotional development, with substance- and sex-specific patterns. These findings highlight the potential harm of THC and EtOH on fetal development and support public health policies aimed at reducing cannabis and alcohol use during pregnancy.

Choline Supplementation Alters Hippocampal Cytokine Levels in Adolescence and Adulthood in an Animal Model of Fetal Alcohol Spectrum Disorders

Alcohol (ethanol) exposure during pregnancy can adversely affect development, with long-lasting consequences that include neuroimmune, cognitive, and behavioral dysfunction. Alcohol-induced alterations in cytokine levels in the hippocampus may contribute to abnormal cognitive and behavioral outcomes in individuals with fetal alcohol spectrum disorders (FASD). Nutritional intervention with the essential nutrient choline can improve hippocampal-dependent behavioral impairments and may also influence neuroimmune function. Thus, we examined the effects of choline supplementation on hippocampal cytokine levels in adolescent and adult rats exposed to alcohol early in development. From postnatal day (PD) 4-9 (third trimester-equivalent), Sprague-Dawley rat pups received ethanol (5.25 g/kg/day) or sham intubations and were treated with choline chloride (100 mg/kg/day) or saline from PD 10-30; hippocampi were collected at PD 35 or PD 60. Age-specific ethanol-induced increases in interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and keratinocyte chemoattractant/human growth-regulated oncogene (KC/GRO) were identified in adulthood, but not adolescence, whereas persistent ethanol-induced increases of interleukin-6 (IL-6) levels were present at both ages. Interestingly, choline supplementation reduced age-related changes in interleukin-1 beta (IL-1β) and interleukin-5 (IL-5) as well as mitigating the long-lasting increase in IFN-γ in ethanol-exposed adults. Moreover, choline influenced inflammatory tone by modulating ratios of pro- to -anti-inflammatory cytokines. These results suggest that ethanol-induced changes in hippocampal cytokine levels are more evident during adulthood than adolescence, and that choline can mitigate some effects of ethanol exposure on long-lasting inflammatory tone.

Effects of prenatal alcohol and delta-9-tetrahydrocannabinol exposure via electronic cigarettes on motor development

BACKGROUND

Prenatal alcohol exposure can lead to a wide range of neurological and behavioral deficits, including alterations in motor domains. However, much less is known about the effects of prenatal cannabis exposure on motor development, despite cannabis being the most consumed illicit drug among women. Cannabis use among pregnant women has become increasingly popular given the widespread perception that consumption is safe during pregnancy. Moreover, alcohol and cannabis are commonly used together, even among pregnant women. Yet few studies have explored the potential consequences of combined prenatal exposure on behavioral domains.

METHODS

Using our previously established model, during gestational days 5 to 20, four groups of pregnant Sprague-Dawley rats were exposed to vaporized alcohol, delta-9-Tetrahydrocannabinol (THC) via electronic (e-) cigarettes, the combination of alcohol and THC, or a vehicle. Following birth, offspring were tested on early sensorimotor development, adolescent motor coordination, and adolescent activity levels.

RESULTS

Prenatal THC e-cigarette exposure delayed sensorimotor development early in life and impaired motor coordination later in early adolescence; combined prenatal alcohol and THC exposure did not have additive effects on sensorimotor development. However, combined prenatal exposure produced hyperactivity among male offspring.

CONCLUSIONS

Prenatal cannabis exposure may lead to impaired motor skills throughout early development and combined exposure with alcohol during gestation may lead to hyperactivity in early adolescence. These findings have important implications for informing pregnant women of the risks to the fetus associated with prenatal cannabis exposure, with and without alcohol, and could influence public policy.

The effects of prenatal nicotine and THC E-cigarette exposure on motor development in rats

RATIONALE

In the USA, nicotine and cannabis are the most common licit and illicit drugs used among pregnant women. Importantly, nicotine and cannabis are now being combined for consumption via e-cigarettes, an increasingly popular delivery device. Both nicotine and tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, cross the placenta barrier. However, the consequences of prenatal cannabis use are not well understood, and less is known about potential combination effects when consumed with nicotine, especially via e-cigarettes.

OBJECTIVE

The present study used a rodent model to examine how prenatal e-cigarette exposure to nicotine, THC, and the combination impacts motor development among offspring.

METHODS

Pregnant Sprague-Dawley rats were exposed to nicotine (36 mg/mL), THC (100 mg/mL), the combination, or vehicle via e-cigarette inhalation from gestational days (GD) 5-20. One sex pair per litter was tested on an early sensorimotor development task (postnatal days [PD] 12-20) and a parallel bar motor coordination task (PD 30-32).

RESULTS

Combined prenatal exposure to nicotine and THC delayed sensorimotor development, even though neither drug produced impairments on their own. In contrast, prenatal exposure to either nicotine or THC impaired motor coordination, whereas combined exposure exacerbated these effects, particularly among females.

CONCLUSIONS

These data illustrate that prenatal exposure to either nicotine or THC may alter motor development, and that the combination may produce more severe effects. These findings have important implications for pregnant women as we better understand the teratogenic effects of these drugs consumed via e-cigarettes.

A Model of Combined Exposure to Nicotine and Tetrahydrocannabinol via Electronic Cigarettes in Pregnant Rats

Nicotine and cannabis are two of the most commonly consumed licit and illicit drugs during pregnancy, often consumed together via e-cigarettes. Vaping is assumed to be a safer alternative than traditional routes of consumption, yet the potential consequences of prenatal e-cigarette exposure are largely unknown, particularly when these two drugs are co-consumed. In a novel co-exposure model, pregnant Sprague-Dawley rats received nicotine (36 mg/mL), tetrahydrocannabinol (THC) (100 mg/mL), the combination, or the vehicle via e-cigarettes daily from gestational days 5–20, mimicking the first and second human trimesters. Maternal blood samples were collected throughout pregnancy to measure drug and metabolite levels, and core body temperatures before and after exposure were also measured. Pregnant dams exposed to combined nicotine and THC had lower plasma nicotine and cotinine levels than those exposed to nicotine alone; similarly, the combined exposure group also had lower plasma THC and THC metabolite (THC-OH and THC-COOH) levels than those exposed to THC alone. Prenatal nicotine exposure gradually decreased initial core body temperatures each day, with chronic exposure, whereas exposure to THC decreased temperatures during the individual sessions. Despite these physiological effects, no changes were observed in food or water intake, weight gain, or basic litter outcomes. The use of this model can help elucidate the effects of co-exposure to THC and nicotine via e-cigarettes on both users and their offspring. Understanding the effects of co-use during pregnancy is critical for improving education for pregnant mothers about prenatal e-cigarette use and has important implications for public policy.

Prenatal alcohol and cannabis exposure can have opposing and region-specific effects on parvalbumin interneuron numbers in the hippocampus

BACKGROUND

We recently showed that alcohol and cannabis can interact prenatally, and in a recent review paper, we identified parvalbumin-positive (PV) interneurons in the hippocampus as a potential point of convergence for these teratogens.

METHODS

A 2 (Ethanol [EtOH], Air) × 2 (tetrahydrocannabinol [THC], Vehicle) design was used to expose pregnant Sprague-Dawley rats to either EtOH or air, in addition to either THC or the inhalant vehicle solution, during gestational days 5-20. Immunohistochemistry was performed to detect PV interneurons in 1 male and 1 female pup from each litter at postnatal day 70.

RESULTS

Significant between-group and subregion-specific effects were found in the dorsal cornu ammonis 1 (CA1) subfield and the ventral dentate gyrus (DG). In the dorsal CA1 subfield, there was an increase in the number of PV interneurons in both the EtOH and EtOH +THC groups, but a decrease with THC alone. There were fewer changes in interneuron numbers overall in the DG, though there was a sex difference, with a decrease in the number of PV interneurons in the THC-exposed group in males. There was also a greater cell layer volume in the DG in the EtOH +THC group than the control group, and in the CA1 region in the EtOH group compared to the control and THC groups.

CONCLUSIONS

Prenatal exposure to alcohol and THC differentially affects parvalbumin-positive interneuron numbers in the hippocampus, indicating that both individual and combined exposure can impact the balance of excitation and inhibition in a structure critically involved in learning and memory processes.

Combined vapor exposure to THC and alcohol in pregnant rats: Maternal outcomes and pharmacokinetic effects

Cannabis is the most frequently used illicit drug among pregnant women, yet the potential consequences of prenatal cannabis exposure on development are not well understood. Electronic cigarettes have become an increasingly popular route of administration among pregnant women, in part to user's perception that e-cigarettes are a safer route for consuming cannabis products. Importantly, half of pregnant women who consume cannabis also report consuming alcohol, but research investigating co-consumption of these drugs is limited, particularly with current routes of administration. The purpose of this study was to establish a co-exposure vapor inhalation model of alcohol and THC in pregnant rats, to ultimately determine the effects on fetal development. Pregnant Sprague-Dawley rats were exposed to moderate doses of THC via e-cigarettes, alcohol, the combination, or vehicle daily from gestational days 5-20. Importantly, pharmacokinetic interactions of alcohol and THC were observed during pregnancy. Combined exposure consistently increased blood alcohol concentrations, indicating that THC alters alcohol metabolism. In addition, THC levels also increased over the course of pregnancy and THC metabolism was altered by alcohol. Alcohol, but not THC, exposure during pregnancy reduced maternal weight gain, despite no group differences in food intake. Neither prenatal alcohol nor THC exposure altered gestational length, litter size, sex ratio or birth weight. However, prenatal alcohol exposure delayed eye opening, and prenatal THC exposure decreased body weights during adolescence among offspring. These individual and synergistic effects suggest that this novel co-exposure vapor inhalation paradigm can effectively be used to expose pregnant dams, exerting some effects on fetal development, while avoiding nutritional confounds, birth complications, or changes in litter size. With this model, we have demonstrated that combining THC and alcohol alters drug metabolism, which could have important consequences on prenatal development.

Altered motor development following late gestational alcohol and cannabinoid exposure in rats

Cannabis is the most commonly used illicit drug among pregnant women, and rates are likely to increase given recent legalization. In addition, half of pregnant women who report consuming cannabis also report drinking alcohol. However, little is known about the consequences of prenatal cannabis alone or in combination with alcohol, particularly with cannabis products that are continually increasing in potency of the primary psychoactive constituent in cannabis, Δ9-tetrahydrocannabinol (THC). The current study investigated the effects of early exposure to cannabinoids during the brain growth spurt on early physical and motor development alone (Experiment 1) or in combination with alcohol (Experiment 2). In Experiment 1, Sprague-Dawley rat pups were exposed to a cannabinoid receptor agonist (CP-55,940 [CP]; 0.1, 0.25, 0.4 mg/kg/day), the drug vehicle, or a saline control from postnatal days (PD) 4-9. In Experiment 2, rat pups were exposed to CP (0.4 mg/kg/day) or the vehicle, and were additionally intubated with alcohol (11.9% v/v; 5.25 g/kg/day) or received a sham intubation. Subjects in both experiments were tested on a motor development task (PD 12-20) and a motor coordination task during adolescence (PD 30-32). Both developmental cannabinoid and alcohol exposure separately decreased body growth throughout development, and combined exposure exacerbated these effects, although only alcohol exposure induced long-term body weight reductions. Developmental cannabinoid exposure advanced early motor development, whereas alcohol exposure delayed development, and subjects given combined exposure did not differ from controls on some measures. Alcohol exposure impaired motor coordination later in life. In contrast, cannabinoid exposure, by itself, did not significantly affect long-term motor coordination, but did exacerbate alcohol-related impairments in motor coordination among females. These results suggest that cannabinoid exposure may not only alter development by itself, but may exacerbate alcohol's teratogenic effects in specific behavioral domains. These findings have important implications not only for individuals affected by prenatal exposure, but also for establishing public policy for women regarding cannabis use during pregnancy.

The effects of alcohol and cannabinoid exposure during the brain growth spurt on behavioral development in rats

Cannabis is the most commonly used illicit drug among pregnant women. Moreover, over half of pregnant women who are consuming cannabis are also consuming alcohol; however, the consequences of combined prenatal alcohol and cannabis exposure on fetal development are not well understood. The current study examined behavioral development following exposure to ethanol (EtOH) and/or CP-55,940 (CP), a cannabinoid receptor agonist. From postnatal days (PD) 4-9, a period of brain development equivalent to the third trimester, Sprague-Dawley rats received EtOH (5.25 g/kg/day) or sham intubation, as well as CP (0.4 mg/kg/day) or vehicle. All subjects were tested on open field activity (PD 18-21), elevated plus maze (PD 25), and spatial learning (PD 40-46) tasks. Both EtOH and CP increased locomotor activity in the open field, and the combination produced more severe overactivity than either exposure alone. Similarly, increases in thigmotaxis in the Morris water maze were caused by either EtOH or CP alone, and were more severe with combined exposure, although only EtOH impaired spatial learning. Finally, developmental CP significantly increased time spent in the open arms on the elevated plus maze. Overall, these data indicate that EtOH and CP produce some independent effects on behavior, and that the combination produces more severe overactivity in the open field. Importantly, these data suggest that prenatal cannabis disrupts development and combined prenatal exposure to alcohol and cannabis may be particularly damaging to the developing fetus, which has implications for the lives of affected individuals and families and also for establishing public health policy.

Dietary choline levels modify the effects of prenatal alcohol exposure in rats

Prenatal alcohol exposure can cause a range of physical and behavioral alterations; however, the outcome among children exposed to alcohol during pregnancy varies widely. Some of this variation may be due to nutritional factors. Indeed, higher rates of fetal alcohol spectrum disorders (FASD) are observed in countries where malnutrition is prevalent. Epidemiological studies have shown that many pregnant women throughout the world may not be consuming adequate levels of choline, an essential nutrient critical for brain development, and a methyl donor. In this study, we examined the influence of dietary choline deficiency on the severity of fetal alcohol effects. Pregnant Sprague-Dawley rats were randomly assigned to receive diets containing 40, 70, or 100% recommended choline levels. A group from each diet condition was exposed to ethanol (6.0g/kg/day) from gestational day 5 to 20 via intubation. Pair-fed and ad lib lab chow control groups were also included. Physical and behavioral development was measured in the offspring. Prenatal alcohol exposure delayed motor development, and 40% choline altered performance on the cliff avoidance task, independent of one another. However, the combination of low choline and prenatal alcohol produced the most severe impairments in development. Subjects exposed to ethanol and fed the 40% choline diet exhibited delayed eye openings, significantly fewer successes in hindlimb coordination, and were significantly overactive compared to all other groups. These data suggest that suboptimal intake of a single nutrient can exacerbate some of ethanol's teratogenic effects, a finding with important implications for the prevention of FASD.

Genetic Versus Pharmacological Assessment of the Role of Cannabinoid Type 2 Receptors in Alcohol Reward-Related Behaviors

BACKGROUND

Emerging evidence suggests that the endocannabinoid system (ECS) is involved in modulating the rewarding effects of abused drugs. Recently, the cannabinoid receptor 2 (CB2R) was shown to be expressed in brain reward circuitry and is implicated in modulating the rewarding effects of alcohol.

METHODS

CB2 ligands and CB2R knockout (KO) mice were used to assess CB2R involvement in alcohol reward-related behavior in 2 well-established behavioral models: limited-access 2-bottle choice drinking and conditioned place preference (CPP). For the pharmacological studies, mice received pretreatments of either vehicle, the CB2R agonist JWH-133 (10 and 20 mg/kg) or the CB2R antagonist AM630 (10 and 20 mg/kg) 30 minutes before behavioral testing. For the genetic studies, CB2R KO mice were compared to wild-type (WT) littermate controls.

RESULTS

CB2R KO mice displayed increased magnitude of alcohol-induced CPP compared to WT mice. Neither agonism nor antagonism of CB2R affected alcohol intake or the expression of CPP, and antagonism of CB2R during CPP acquisition trials also did not affect CPP.

CONCLUSIONS

The CB2R KO CPP data provide partial support for the hypothesis that CB2Rs are involved in the modulation of alcohol reward-related behaviors. However, pharmacological manipulation of CB2Rs did not alter alcohol's rewarding effects in the alcohol-seeking models used here. These results highlight the importance of pharmacological validation of effects seen with lifetime KO models. Given the ongoing efforts toward medications development, future studies should continue to explore the role of the CB2R as a potential neurobiological target for the treatment of alcohol use disorders.

Effects of Chronic Stress on Alcohol Reward- and Anxiety-Related Behavior in High- and Low-Alcohol Preferring Mice

BACKGROUND

Stress exposure (SE) during adolescence is associated with an increased risk for the development of alcohol use disorders (AUDs). Past research has shown that SE during adolescence increases voluntary alcohol consumption in mice during adulthood; however, little is known about the positive or negative motivational aspects of this relationship.

METHODS

High-alcohol preferring (HAP2) and low-alcohol preferring (LAP2) male mice were exposed to stress during adolescence, stress during adulthood, or no stress. After a 30-day interim, subjects were exposed to alcohol-induced place and footshock-induced fear conditioning procedures to measure stress-induced behavioral alterations during adulthood.

RESULTS

SE during adolescence did not increase the magnitude of alcohol-induced conditioned place preference (CPP), as hypothesized, but increased the magnitude of conditioned fear, as measured by fear-potentiated startle (FPS), in HAP2 subjects only. Regardless of stress treatment group, LAP2 subjects showed greater alcohol-induced CPP expression than HAP2 mice. HAP2 mice also showed greater FPS than LAP2 mice, as previously shown.

CONCLUSIONS

These results in mice, taken together with past research, suggest that mice exposed to stress during adolescence do not increase alcohol consumption during adulthood because of a greater sensitivity to the rewarding effects of alcohol, as measured via place conditioning. These results in mice also suggest that humans exposed to stress during adolescence may be more susceptible to developing anxiety during adulthood. The findings may be particularly relevant for humans with a familial history of AUDs.