Effect of Gabapentin on Sleep and Event-Related Oscillations (EROs) in Rats Exposed to Chronic Intermittent Ethanol Vapor and Protracted Withdrawal

Use of a Fitbit-like device in rats: Sex differences, relation to EEG sleep, and use to measure the long-term effects of adolescent ethanol exposure

BACKGROUND

Sleep difficulties and rhythm disturbances are some of the problems associated with adolescent binge drinking. Recently, animal models of alcohol-induced insomnia have been developed. However, studies in human subjects have recently focused not only on nighttime EEG findings but also on daytime sleepiness and disrupted activity levels as typically measured by activity tracking devices such as the "Fitbit." We sought to develop and test a Fitbit-like device (the "FitBite") in rats and use it to track rest-activity cycles following adolescent alcohol exposure.

METHODS

The effects of 5 weeks of adolescent ethanol vapor or control conditions were evaluated in 48 male and female Wistar rats using FitBite activity while intoxicated, and during acute (24 h post-vapor exposure) and chronic withdrawal (4 weeks post-vapor exposure). Data were analyzed using activity count and cosinor analyses. Fourteen rats were subsequently implanted with cortical electrodes, and data from the FitBite were compared with EEG data to determine how well the FitBite could identify sleep and activity cycles.

RESULTS

Female rats were generally more active than males, with higher circadian rhythm amplitudes and mesors (rhythm-adjusted means) across a 24-h period. There were significant correlations between EEG-estimated sleep and activity counts using the FitBite. When the rats were tested during intoxication after 4 weeks of ethanol vapor exposure, they had significantly less overall activity. Disruptions in circadian rhythm were also found with significant decreases in the circadian amplitude, mesor, and a later shift in the acrophase. At 24 h of ethanol withdrawal, rats had more episodes of activity with shorter durations during the daytime, when rats are expected to spend more of their time sleeping. This effect remained at 4 weeks following withdrawal, but circadian rhythm disruptions were no longer present.

CONCLUSIONS

A Fitbit-like device can be successfully used in rats to assess rest-activity cycles. Adolescent alcohol exposure produced circadian rhythm disturbances that were not observed after withdrawal. Fragmentation of ultradian rest-activity cycles during the light period was found at 24 h and 4 weeks after withdrawal and support data demonstrating the presence of sleep disturbance long after alcohol withdrawal.

Chronic intermittent ethanol during adolescence and adulthood alters dendritic spines in the primary motor and visual cortex in rats

Prolonged adolescent binge drinking can disrupt sleep quality and increase the likelihood of alcohol-induced sleep disruptions in young adulthood in rodents and in humans. Striking changes in spine density and morphology have been seen in many cortical and subcortical regions after adolescent alcohol exposure in rats. However, there is little known about the impact of alcohol exposure on dendritic spines in the same motor and sensory cortices that EEG sleep is typically recorded from in rats. The aim of this study is to investigate whether an established model of chronic intermittent ethanol vapor in rats that has been demonstrated to disrupt sleep during adolescence or adulthood, also significantly alters cortical dendritic spine density and morphology. To this end, adolescent and adult Wistar rats were exposed to 5 weeks of ethanol vapor or control air exposure. After a 13-day withdrawal, primary motor cortex (M1) and primary/secondary visual cortex (V1/V2) layer V dendrites were analyzed for differences in spine density and morphology. Spines were classified into four categories (stubby, long, filopodia, and mushroom) based on the spine length and the width of the spine head and neck. The main results indicate an age-specific effect of adolescent intermittent ethanol exposure decreasing spine density in the M1 cortex compared to age-matched controls. Reductions in the density of M1 long-shaped spine subclassifications were seen in adolescent ethanol-exposed rats, but not adult-exposed rats, compared to their air-controls. Irrespective of age, there was an overall reduction produced by ethanol exposure on the density of filopodia and the length of long-shaped spines in V1/V2 cortex as compared to their air-exposed controls. Together, these data add to growing evidence that some cortical circuits are vulnerable to the effects of alcohol during adolescence and begin to elucidate potential mechanisms that may influence brain plasticity following early alcohol use.

Adolescent alcohol exposure increases orexin-A/hypocretin-1 in the anterior hypothalamus

Adolescence is a time of marked changes in sleep, neuromaturation, and alcohol use. While there is substantial evidence that alcohol disrupts sleep and that disrupted sleep may play a role in the development of alcohol use disorders (AUD), there is very little known about the brain mechanisms underlying this phenomenon. The orexin (also known as hypocretin) system is fundamental for a number of homeostatic mechanisms, including the initiation and maintenance of wakefulness that may be impacted by adolescent alcohol exposure. The current study investigated the impact of adolescent ethanol exposure on adult orexin-A/hypocretin-1 immunoreactive (orexin-A + IR) cells in hypothalamic nuclei in two models of adolescent intermittent ethanol (AIE) exposure. Both models assess adult hypothalamic orexin following either an AIE vapor exposure paradigm, or an AIE intragastric gavage paradigm during adolescence. Both AIE exposure models found that binge levels of ethanol intoxication during adolescence significantly increased adult orexin-A + IR expression in the anterior hypothalamic nucleus (AHN). Further, both AIE models found no change in orexin-A + IR in the posterior hypothalamic area (PH), perifornical nucleus (PeF), dorsomedial hypothalamic nucleus dorsal part (DMD) or lateral hypothalamic area (LH). However, AIE vapor exposure reduced orexin-A + IR in the paraventricular nucleus (PVN), but AIE gavage exposure did not. These findings suggest that the AHN orexinergic system is increased in adults following binge-like patterns of intoxication during adolescence. Altered adult AHN orexin could contribute to long-lasting changes in sleep.

Gabapentinoids for treatment of alcohol use disorder: A systematic review and meta-analysis

OBJECTIVE

Gabapentin (GBP) and pregabalin (PGB) have been used to treat alcohol use disorder (AUD) and alcohol withdrawal, but with inconsistent results. In this meta-analysis, we explored the effects of GBP/PGB treatment on AUD and their effects on withdrawal, craving, depression, and sleep disturbance in AUD patients.

METHODS

We carried out a systematic review and meta-analysis of randomized controlled trials comparing the effects of GBP/PGB on AUD with those of a placebo or control treatment. Electronic databases were searched for relevant articles published before September 2019. The primary outcome was defined as the efficacy measure on achieving abstinence or reducing alcohol consumption in a hierarchical order. We included 16 studies in our meta-analysis.

RESULTS

Overall, GBP had no significant benefit comparing to placebo or control treatment (Hedges' g = 0.0725, p = 0.6743). For specific alcohol-related outcome, GBP had significant effect on percentage of heavy drink (Hedges' g = 0.5478, p = 0.0441) and alcohol withdrawal symptoms (Hedges' g = 0.2475, p = 0.0425). GBP/PGB did not have significant beneficial effect on craving, depressive symptoms, or sleep disturbance. Instability was shown in sensitivity analyses of some above results.

CONCLUSIONS

GBP may be helpful to reduce AUD patients' heavy drinking behavior and withdrawal, but more studies are needed for drawing conclusions.

PSPH-D-18-00526: Effect of a dual orexin receptor antagonist (DORA-12) on sleep and event-related oscillations in rats exposed to ethanol vapor during adolescence

RATIONALE

Sleep difficulties are one of the problems associated with adolescent binge drinking. However, the mechanisms underlying adolescent alcohol-associated sleep disturbances and potential targets for therapy remain under investigated. Orexin receptor antagonists may have therapeutic value in the treatment of insomnia, yet the use of this class of drugs in the treatment of sleep disturbances following adolescent alcohol exposure has not been studied.

OBJECTIVES

This study employed a model whereby ethanol vapor exposure occurred for 5 weeks during adolescence (AIE), and waking event-related oscillations (EROs) and EEG sleep were subsequently evaluated in young adult rats. The ability of two doses (10, 30 mg/kg PO) of a dual orexin receptor antagonist (DORA-12) to modify sleep, EEG, and EROs was investigated in AIE rats and controls.

RESULTS

Adolescent vapor exposure was found to produce a fragmentation of sleep, in young adults, that was partially ameliorated by DORA-12. DORA-12 also produced increases in delta and theta power in waking EROs recorded before sleep, and deeper sleep as indexed by increases in delta and theta power in the sleep EEG in both ethanol and control rats. Rats given DORA-12 also fell asleep faster than vehicle-treated rats as measured by a dose-dependent reduction in the latency to both the first slow wave and REM sleep episodes.

CONCLUSIONS

This study showed that DORA-12 can affect the sleep disturbance that is associated with a history of adolescent ethanol exposure and also has several other sleep-promoting effects that are equivalent in both ethanol and control rats.

Effects of an Orexin-2 Receptor Antagonist on Sleep and Event-Related Oscillations in Female Rats Exposed to Chronic Intermittent Ethanol During Adolescence

BACKGROUND

Alcohol use is on the rise among women in the United States which is especially concerning since women who drink have a higher risk of alcohol-related problems. Orexin (hypocretin) receptor antagonists may have some therapeutic value for alcohol-induced insomnia; however, the use of this class of drugs following female adolescent binge drinking is limited. The current study will address whether adolescent intermittent ethanol (AIE) in female rats can result in lasting changes in sleep pathology and whether orexin-targeted treatment can alleviate these deficits.

METHODS

Following a 5-week AIE vapor model, young adult rats were evaluated on waking event-related oscillations (EROs) and EEG sleep. Subsequently, AIE rats were treated with orexin receptor 2 (OX₂ R) antagonist (MK-1064; 10, 20mg/kg) to test for modifications in sleep pathology and waking ERO.

RESULTS

Female AIE rats exhibited lasting changes in sleep compared to controls. This was demonstrated by increased fragmentation of slow wave sleep (SWS) and rapid eye movement sleep, as well as reductions in delta and theta power during SWS. There was no impact of AIE on waking EROs. Acute MK-1064 hastened SWS onset and increased the number of SWS episodes, without increasing sleep fragmentation in AIE and controls. While treatment with MK-1064 did not impact sleep EEG spectra, waking ERO energy was increased in delta, theta, and beta frequency bands.

CONCLUSIONS

These results demonstrate that AIE can produce lasting changes in sleep in female rats, highly similar to what we previously found in males. Additionally, while the OX₂ R antagonist promoted sleep in both alcohol-exposed and unexposed rats, it did not reverse most of the alcohol-induced disruptions in sleep. Thus, OX₂ R antagonism may serve as a potential therapeutic strategy for the treatment of insomnia, but not the specific signs of alcohol-induced insomnia.

Effect of suvorexant on event-related oscillations and EEG sleep in rats exposed to chronic intermittent ethanol vapor and protracted withdrawal

STUDY OBJECTIVES

Insomnia is a prominent complaint in patients with alcohol use disorders (AUD). However, despite the importance of sleep in the maintenance of sobriety, treatment options for sleep disturbance associated with a history of AUD are currently limited. Recent clinical trials have demonstrated that suvorexant, a dual Hct/OX receptor antagonist, normalizes sleep in patients with primary insomnia; yet, its potential for the treatment of sleep pathology associated with AUD has not been investigated in either preclinical or clinical studies.

METHODS

This study employed a model whereby ethanol vapor exposure or control conditions were administered for 8 weeks to adult rats. Waking event-related oscillations (EROs) and EEG sleep were evaluated at baseline before exposure and again following 24 hr of withdrawal from the exposure. Subsequently, the ability of vehicle (VEH) and two doses (10, 30 mg/kg IP) of suvorexant to modify EROs, sleep, and the sleep EEG was investigated.

RESULTS

After 24 hr following EtOH withdrawal, the ethanol-treated group had increases in waking ERO θ and β activity, more fragmented sleep (shorter duration and increased frequency of slow wave (SW) and rapid eye movement [REM] sleep episodes), and increased θ and β power in REM and SW sleep. Suvorexant induced a dose-dependent decrease in the latency to REM and SW sleep onsets but also produced REM and SW sleep fragmentation and increased β energy in waking EROs when compared with VEH.

CONCLUSIONS

Taken together, these studies suggest that suvorexant has overall sleep-promoting effects, but it may exacerbate some aspects of sleep and EEG pathology.

Mechanisms of Persistent Neurobiological Changes Following Adolescent Alcohol Exposure: NADIA Consortium Findings

The Neurobiology of Adolescent Drinking in Adulthood (NADIA) Consortium has focused on the impact of adolescent binge drinking on brain development, particularly on effects that persist into adulthood. Adolescent binge drinking is common, and while many factors contribute to human brain development and alcohol use during adolescence, animal models are critical for understanding the specific consequences of alcohol exposure during this developmental period and the underlying mechanisms. Using adolescent intermittent ethanol (AIE) exposure models, NADIA investigators identified long-lasting AIE-induced changes in adult behavior that are consistent with observations in humans, such as increased alcohol drinking, increased anxiety (particularly social anxiety), increased impulsivity, reduced behavioral flexibility, impaired memory, disrupted sleep, and altered responses to alcohol. These behavioral changes are associated with multiple molecular, cellular, and physiological alterations in the brain that persist long after AIE exposure. At the molecular level, AIE results in long-lasting changes in neuroimmune/trophic factor balance and epigenetic-microRNA (miRNA) signaling across glia and neurons. At the cellular level, AIE history is associated in adulthood with reduced expression of cholinergic, serotonergic, and dopaminergic neuron markers, attenuated cortical thickness, decreased neurogenesis, and altered dendritic spine and glial morphology. This constellation of molecular and cellular adaptations to AIE likely contributes to observed alterations in neurophysiology, measured by synaptic physiology, EEG patterns, and functional connectivity. Many of these AIE-induced brain changes replicate findings seen in postmortem brains of humans with alcohol use disorder (AUD). NADIA researchers are now elucidating mechanisms of these adaptations. Emerging data demonstrate that exercise, antiinflammatory drugs, anticholinesterases, histone deacetylase inhibitors, and other pharmacological compounds are able to prevent (administered during AIE) and/or reverse (given after AIE) AIE-induced pathology in adulthood. These studies support hypotheses that adolescent binge drinking increases risk of adult hazardous drinking and influences brain development, and may provide insight into novel therapeutic targets for AIE-induced neuropathology and AUDs.

Effect of gabapentin on sleep and delta and theta EEG power in adult rats exposed to chronic intermittent ethanol vapor and protracted withdrawal during adolescence

RATIONALE

Adolescents and young adults with alcohol problems may also have sleep difficulties. However, whether these sleep problems are a result of a history of drinking or arise due to other comorbid disorders is difficult to disentangle in human studies. Additionally, the mechanisms underlying adolescent alcohol-induced sleep disturbances and potential targets for therapy also remain under-investigated. Recent clinical trials have demonstrated that the anticonvulsant and analgesic drug gabapentin may have therapeutic value in normalizing sleep quality in adult recovering alcoholics, yet its potential for the treatment of adolescent sleep disturbances has not been investigated.

OBJECTIVES

This study sought to evaluate the effects of a history of 5 weeks of chronic intermittent ethanol vapor exposure, administered during adolescence (AIE), on EEG sleep, in young adult rats (n = 29). The ability of two doses of gabapentin (30, 120 mg/kg) to modify sleep and slow wave activity were also investigated in these young adult rats exposed to alcohol vapor during adolescence.

RESULTS

Adolescent vapor exposure in the rat was found to result in deficits in delta (1-4 Hz) and theta (4-8 Hz) power during slow wave sleep. Administration of gabapentin caused a "normalization" of the delta power deficits but did not affect theta power.

CONCLUSIONS

This report suggests that the potential mechanisms and therapeutic targets for sleep disturbance associated with adolescent alcohol exposure can be studied in preclinical models and that gabapentin may show partial efficacy in ameliorating these sleep deficits.