Temporal pattern in consumption of the first drink of the day in alcohol-dependent persons

Sexually dimorphic role of circadian clock genes in alcohol drinking behavior

Sex differences in alcohol use and abuse are pervasive and carry important implications for the prevention and treatment of alcohol use disorder (AUD), yet insight into underlying sexually dimorphic mechanisms is limited. Growing experimental and clinical evidence points to an important influence of circadian rhythms and circadian clock genes in the control of alcohol drinking behavior and AUD. Sex differences in the expression of circadian rhythms and in the molecular circadian clock that drive these rhythms have been reported in humans and animals. While studying the role of striatal circadian clock gene expression in the control of affective and goal-directed behaviors, we uncovered a novel sexually dimorphic function of the clock genes Bmal1 and Per2 in the control of voluntary alcohol consumption in mice, which may contribute to sex differences in alcohol drinking behavior. In this mini review, we briefly discuss relevant literature on AUD, circadian rhythms and clock genes, and on sex differences in these domains, and describe our own findings on clock genes as sexually dimorphic regulators of alcohol drinking behavior in mice.

Momentary associations between stress and alcohol craving in the naturalistic environment: differential associations for Black and White young adults

BACKGROUND AND AIMS

Black drinkers compared with White drinkers experience more alcohol-related problems. Examination of social determinants of inequities in alcohol problems is needed. The current study measured (1) associations between acute stress and alcohol craving in the naturalistic environment for self-identified Black and White individuals who drink alcohol and (2) whether a history of attention deficit hyperactivity disorder (ADHD) moderated these associations.

DESIGN AND SETTING

Observational study using ecological momentary assessment (EMA) to collect data from participants at six semi-random time-points throughout the day during a 10-day period. A series of three-level multi-level models examined between- and within-person associations for stress and alcohol and tested if these associations differed for Black and White adults.

PARTICIPANTS

Participants were 229 adult drinkers (aged 21-35 years) who completed a larger study examining alcohol response for Black and White adults with and without a history of childhood ADHD.

MEASUREMENTS

Momentary stress and alcohol craving, ADHD history and socio-demographic characteristics (i.e. racial identity, sex, age, current education level, household income) were assessed. Participants were required to self-identify as either 'African American or Black' or 'European American or White'.

FINDINGS

Significant racial identity × stress interactions indicated that associations between stress and craving were stronger for Black compared with White adults across the 10-day period (between-person: B = 0.14, P = 0.007), concurrently within a given EMA time-point (within-person: B = 0.04, P = 0.001) and prospectively from time-point to time-point (within-person: B = 0.05, P = 0.001). Results remained while accounting for income × stress interactions.

CONCLUSIONS

Acute stress appears to be more strongly related to alcohol craving in self-identified Black compared with self-identified White individuals. This provides support for policy changes to eliminate structural inequities that increase stress exposure and the development of just-in-time culturally responsive interventions focused on coping with acute stress for Black individuals.

Circadian rhythms and substance use disorders: A bidirectional relationship

The circadian system organizes circadian rhythms (biological cycles that occur around 24 h) that couple environmental cues (zeitgebers) with internal functions of the organism. The misalignment between circadian rhythms and external cues is known as chronodisruption and contributes to the development of mental, metabolic and other disorders, including cancer, cardiovascular diseases and addictive disorders. Drug addiction represents a global public health concern and affects the health and well-being of individuals, families and communities. In this manuscript, we reviewed evidence indicating a bidirectional relationship between the circadian system and the development of addictive disorders. We provide information on the interaction between the circadian system and drug addiction for each drug or drug class (alcohol, cannabis, hallucinogens, psychostimulants and opioids). We also describe evidence showing that drug use follows a circadian pattern, which changes with the progression of addiction. Furthermore, clock gene expression is also altered during the development of drug addiction in many brain areas related to drug reward, drug seeking and relapse. The regulation of the glutamatergic and dopaminergic neurocircuitry by clock genes is postulated to be the main circadian mechanism underlying the escalation of drug addiction. The bidirectional interaction between the circadian system and drug addiction seems to be mediated by the effects caused by each drug or class of drugs of abuse. These studies provide new insights on the development of successful strategies aimed at restoring/stabilizing circadian rhythms to reduce the risk for addiction development and relapse.

Is there a 24-hour rhythm in alcohol craving and does it vary by sleep/circadian timing?

Increasing evidence implicates sleep/circadian factors in alcohol use; however, the role of such factors in alcohol craving has received scant attention. Prior research suggests a 24-hour rhythm in related processes (e.g., reward motivation), but more research directly investigating a rhythm in craving is needed. Moreover, prior evidence is ambiguous whether such a rhythm in alcohol craving may vary by sleep/circadian timing. To examine these possibilities, 36 late adolescents (18-22 years of age; 61% female) with regular alcohol use but without a current alcohol use disorder were recruited to complete smartphone reports of alcohol craving intensity six times a day for two weeks. During these two weeks, participants wore wrist actigraphs and completed two in-lab assessments (on Thursday and Sunday) of dim light melatonin onset (DLMO). Average actigraphically derived midpoint of sleep on weekends and average DLMO were used as indicators of sleep and circadian timing, respectively. Multilevel cosinor analysis revealed a 24-hour rhythm in alcohol craving. Findings across the sleep and circadian timing variables converged to suggest that sleep/circadian timing moderated the 24-hour rhythm in alcohol craving. Specifically, people with later sleep/circadian timing had later timing of peak alcohol craving. These findings add to the growing evidence of potential circadian influences on reward-related phenomena and suggest that greater consideration of sleep and circadian influences on alcohol craving may be useful for understanding alcohol use patterns and advancing related interventions.

DAILY-A Personalized Circadian Zeitgeber Therapy as an Adjunctive Treatment for Alcohol Use Disorder Patients: Study Protocol for a Randomized Controlled Trial

Background: Hallmarks of alcohol use disorder (AUD) are disturbances of circadian rhythms and everyday structures. While circadian rhythms dictate the timing of daily recurring activities such as sleep, activity, and meals, conversely, these activities represent time cues, so called Zeitgebers, that the circadian system uses to synchronize with the environment. Here we present a study protocol for our newly developed therapy approach for AUD patients, in which we take advantage of this mutual influence and stabilize and strengthen their circadian system by creating strict daily schedules for daily Zeitgeber activities. Since every person has a circadian system with its own characteristics and is subject to social obligations, the daily plans are personalized for each test person. Our hypothesis is that a regular exposure to Zeitgebers stabilizes behavioral and physiological circadian rhythms and thereby reduces the risk of alcohol relapses and depressive symptoms and facilitates physical recovery in AUD patients during the 1st weeks of their addiction therapy. Methods/design: The study is a 6-weeks single site trial with a controlled, randomized, single-blinded, parallel-group design including patients with a diagnosis of AUD. The study runs parallel to the standard addiction therapy of the clinic. Patients are randomly assigned to either an intervention group (DAILY) or a sham control group (placebo treatment). Questionnaires and physiological assessments of both groups are conducted before and immediately after the intervention or control treatment. According to our hypothesis, the primary outcomes of this study are improvements of regularity, alcohol consumption, and relapse rate in AUD patients compared to AUD patients receiving control treatment. Secondary outcomes are reduced depressive symptoms and increased physical recovery. Discussion: This study is a randomized controlled trial to investigate the efficacy of a personalized circadian Zeitgeber therapy as an adjunctive treatment for alcohol use disorder patients. The overall goal of this and more extended future studies is the development of an adjunctive therapy for AUD patients that is uncomplicated in its use and easy to implement in the clinical and everyday routine. Trial registration: This study is registered at the German Clinical Trial Register with the trial number DRKS00019093 on November 28, 2019.

Circadian Mechanisms in Alcohol Use Disorder and Tissue Injury

Heavy use of alcohol can lead to addictive behaviors and to eventual alcohol-related tissue damage. While increased consumption of alcohol has been attributed to various factors including level of alcohol exposure and environmental factors such as stress, data from behavioral scientists and physiological researchers are revealing roles for the circadian rhythm in mediating the development of behaviors associated with alcohol use disorder as well as the tissue damage that drives physiological disease. In this work, we compile recent work on the complex mutually influential relationship that exists between the core circadian rhythm and the pharmacodynamics of alcohol. As we do so, we highlight implications of the relationship between alcohol and common circadian mechanisms of effected organs on alcohol consumption, metabolism, toxicity, and pathology.

Drosophila: An Emergent Model for Delineating Interactions between the Circadian Clock and Drugs of Abuse

Endogenous circadian oscillators orchestrate rhythms at the cellular, physiological, and behavioral levels across species to coordinate activity, for example, sleep/wake cycles, metabolism, and learning and memory, with predictable environmental cycles. The 21st century has seen a dramatic rise in the incidence of circadian and sleep disorders with globalization, technological advances, and the use of personal electronics. The circadian clock modulates alcohol- and drug-induced behaviors with circadian misalignment contributing to increased substance use and abuse. Invertebrate models, such as Drosophila melanogaster, have proven invaluable for the identification of genetic and molecular mechanisms underlying highly conserved processes including the circadian clock, drug tolerance, and reward systems. In this review, we highlight the contributions of Drosophila as a model system for understanding the bidirectional interactions between the circadian system and the drugs of abuse, alcohol and cocaine, and illustrate the highly conserved nature of these interactions between Drosophila and mammalian systems. Research in Drosophila provides mechanistic insights into the corresponding behaviors in higher organisms and can be used as a guide for targeted inquiries in mammals.

Circadian Modulation of Alcohol-Induced Sedation and Recovery in Male and Female Drosophila

Delineating the factors that affect behavioral and neurological responses to alcohol is critical to facilitate measures for preventing or treating alcohol abuse. The high degree of conserved molecular and physiological processes makes Drosophila melanogaster a valuable model for investigating circadian interactions with alcohol-induced behaviors and examining sex-specific differences in alcohol sensitivity. We found that wild-type Drosophila exhibited rhythms in alcohol-induced sedation under light-dark and constant dark conditions with considerably greater alcohol exposure necessary to induce sedation during the late (subjective) day and peak sensitivity to alcohol occurring during the late (subjective) night. The circadian clock also modulated the recovery from alcohol-induced sedation with flies regaining motor control significantly faster during the late (subjective) day. As predicted, the circadian rhythms in sedation and recovery were absent in flies with a mutation in the circadian gene period or arrhythmic flies housed in constant light conditions. Flies lacking a functional circadian clock were more sensitive to the effects of alcohol with significantly longer recovery times. Similar to other animals and humans, Drosophila exhibit sex-specific differences in alcohol sensitivity. We investigated whether the circadian clock modulated the rhythms in the loss-of-righting reflex, alcohol-induced sedation, and recovery differently in males and females. We found that both sexes demonstrated circadian rhythms in the loss-of-righting reflex and sedation with the differences in alcohol sensitivity between males and females most pronounced during the late subjective day. Recovery of motor reflexes following alcohol sedation also exhibited circadian modulation in male and female flies, although the circadian clock did not modulate the difference in recovery times between the sexes. These studies provide a framework outlining how the circadian clock modulates alcohol-induced behaviors in Drosophila and identifies sexual dimorphisms in the circadian modulation of alcohol behaviors.

Circadian Mechanisms Underlying Reward-Related Neurophysiology and Synaptic Plasticity

Evidence from clinical and preclinical research provides an undeniable link between disruptions in the circadian clock and the development of psychiatric diseases, including mood and substance abuse disorders. The molecular clock, which controls daily patterns of physiological and behavioral activity in living organisms, when desynchronized, may exacerbate or precipitate symptoms of psychiatric illness. One of the outstanding questions remaining in this field is that of cause and effect in the relationship between circadian rhythm disruption and psychiatric disease. Focus has recently turned to uncovering the role of circadian proteins beyond the maintenance of homeostatic systems and outside of the suprachiasmatic nucleus (SCN), the master pacemaker region of the brain. In this regard, several groups, including our own, have sought to understand how circadian proteins regulate mechanisms of synaptic plasticity and neurotransmitter signaling in mesocorticolimbic brain regions, which are known to be critically involved in reward processing and mood. This regulation can come in the form of direct transcriptional control of genes central to mood and reward, including those associated with dopaminergic activity in the midbrain. It can also be seen at the circuit level through indirect connections of mesocorticolimbic regions with the SCN. Circadian misalignment paradigms as well as genetic models of circadian disruption have helped to elucidate some of the complex interactions between these systems and neural activity influencing behavior. In this review, we explore findings that link circadian protein function with synaptic adaptations underlying plasticity as it may contribute to the development of mood disorders and addiction. In light of recent advances in technology and sophisticated methods for molecular and circuit-level interrogation, we propose future directions aimed at teasing apart mechanisms through which the circadian system modulates mood and reward-related behavior.

The Molecular Circadian Clock and Alcohol-Induced Liver Injury

Emerging evidence from both experimental animal studies and clinical human investigations demonstrates strong connections among circadian processes, alcohol use, and alcohol-induced tissue injury. Components of the circadian clock have been shown to influence the pathophysiological effects of alcohol. Conversely, alcohol may alter the expression of circadian clock genes and the rhythmic behavioral and metabolic processes they regulate. Therefore, we propose that alcohol-mediated disruption in circadian rhythms likely underpins many adverse health effects of alcohol that cut across multiple organ systems. In this review, we provide an overview of the circadian clock mechanism and showcase results from new studies in the alcohol field implicating the circadian clock as a key target of alcohol action and toxicity in the liver. We discuss various molecular events through which alcohol may work to negatively impact circadian clock-mediated processes in the liver, and contribute to tissue pathology. Illuminating the mechanistic connections between the circadian clock and alcohol will be critical to the development of new preventative and pharmacological treatments for alcohol use disorders and alcohol-mediated organ diseases.

Dissociation between diurnal cycles in locomotor activity, feeding behavior and hepatic PERIOD2 expression in chronic alcohol-fed mice

Chronic alcohol consumption contributes to fatty liver disease. Our studies revealed that the hepatic circadian clock is disturbed in alcohol-induced hepatic steatosis, and effects of chronic alcohol administration upon the clock itself may contribute to steatosis. We extended these findings to explore the effects of chronic alcohol treatment on daily feeding and locomotor activity patterns. Mice were chronically pair-fed ad libitum for 4 weeks using the Lieber-DeCarli liquid diet, with calorie-controlled liquid and standard chow diets as control groups. Locomotor activity, feeding activity, and real-time bioluminescence recording of PERIOD2::LUCIFERASE expression in tissue explants were measured. Mice on liquid control and chow diets exhibited normal profiles of locomotor activity, with a ratio of 22:78% day/night activity and a peak during early night. This pattern was dramatically altered in alcohol-fed mice, marked by a 49:51% ratio and the absence of a distinct peak. While chow-diet fed mice had a normal 24:76% ratio of feeding activity, with a peak in the early night, this pattern was dramatically altered in both liquid-diet groups: mice had a 43:57% ratio, and an absence of a distinct peak. Temporal differences were also observed between the two liquid-diet groups during late day. Cosinor analysis revealed a ∼4-h and ∼6-h shift in the alcohol-fed group feeding and locomotor activity rhythms, respectively. Analysis of hepatic PER2 expression revealed that the molecular clock in alcohol-fed and control liquid-diet mice was shifted by ∼11 h and ∼6 h, respectively. No differences were observed in suprachiasmatic nucleus explants, suggesting that changes in circadian phase in the liver were generated independently from the central clock. These results suggest that chronic alcohol consumption and a liquid diet can differentially modulate the daily rhythmicity of locomotor and feeding behaviors, aspects that might contribute to disturbances in the circadian timing system and development of hepatic steatosis.

Diurnal and twenty-four hour patterning of human diseases: acute and chronic common and uncommon medical conditions

The symptom intensity and mortality of human diseases, conditions, and syndromes exhibit diurnal or 24 h patterning, e.g., skin: atopic dermatitis, urticaria, psoriasis, and palmar hyperhidrosis; gastrointestinal: esophageal reflux, peptic ulcer (including perforation and hemorrhage), cyclic vomiting syndrome, biliary colic, hepatic variceal hemorrhage, and proctalgia fugax; infection: susceptibility, fever, and mortality; neural: frontal, parietal, temporal, and occipital lobe seizures, Parkinson's and Alzheimer's disease, hereditary progressive dystonia, and pain (cancer, post-surgical, diabetic neuropathic and foot ulcer, tooth caries, burning mouth and temporomandibular syndromes, fibromyalgia, sciatica, intervertebral vacuum phenomenon, multiple sclerosis muscle spasm, and migraine, tension, cluster, hypnic, and paroxysmal hemicranial headache); renal: colic and nocturnal enuresis and polyuria; ocular: bulbar conjunctival redness, keratoconjunctivitis sicca, intraocular pressure and anterior ischemic optic neuropathy, and recurrent corneal erosion syndrome; psychiatric/behavioral: major and seasonal affective depressive disorders, bipolar disorder, parasuicide and suicide, dementia-associated agitation, and addictive alcohol, tobacco, and heroin cravings and withdrawal phenomena; plus autoimmune and musculoskeletal: rheumatoid arthritis, osteoarthritis, axial spondylarthritis, gout, Sjögren's syndrome, and systemic lupus erythematosus. Knowledge of these and other 24 h patterns of human pathophysiology informs research of their underlying circadian and other endogenous mechanisms, external temporal triggers, and more effective patient care entailing clinical chronopreventive and chronotherapeutic strategies.

The FlyBar: administering alcohol to flies

Fruit flies (Drosophila melanogaster) are an established model for both alcohol research and circadian biology. Recently, we showed that the circadian clock modulates alcohol sensitivity, but not the formation of tolerance. Here, we describe our protocol in detail. Alcohol is administered to the flies using the FlyBar. In this setup, saturated alcohol vapor is mixed with humidified air in set proportions, and administered to the flies in four tubes simultaneously. Flies are reared under standardized conditions in order to minimize variation between the replicates. Three-day old flies of different genotypes or treatments are used for the experiments, preferably by matching flies of two different time points (e.g., CT 5 and CT 17) making direct comparisons possible. During the experiment, flies are exposed for 1 hr to the pre-determined percentage of alcohol vapor and the number of flies that exhibit the Loss of Righting reflex (LoRR) or sedation are counted every 5 min. The data can be analyzed using three different statistical approaches. The first is to determine the time at which 50% of the flies have lost their righting reflex and use an Analysis of the Variance (ANOVA) to determine whether significant differences exist between time points. The second is to determine the percentage flies that show LoRR after a specified number of minutes, followed by an ANOVA analysis. The last method is to analyze the whole times series using multivariate statistics. The protocol can also be used for non-circadian experiments or comparisons between genotypes.

Circadian rhythms and addiction: mechanistic insights and future directions

Circadian rhythms are prominent in many physiological and behavioral functions. Circadian disruptions either by environmental or molecular perturbation can have profound health consequences, including the development and progression of addiction. Both animal and humans studies indicate extensive bidirectional relationships between the circadian system and drugs of abuse. Addicted individuals display disrupted rhythms, and chronic disruption or particular chronotypes may increase the risk for substance abuse and relapse. Moreover, polymorphisms in circadian genes and an evening chronotype have been linked to mood and addiction disorders, and recent efforts suggest an association with the function of reward neurocircuitry. Animal studies are beginning to determine how altered circadian gene function results in drug-induced neuroplasticity and behaviors. Many studies suggest a critical role for circadian rhythms in reward-related pathways in the brain and indicate that drugs of abuse directly affect the central circadian pacemaker. In this review, we highlight key findings demonstrating the importance of circadian rhythms in addiction and how future studies will reveal important mechanistic insights into the involvement of circadian rhythms in drug addiction.

Circadian phase determines effects of repeated ethanol vapor exposure and withdrawal on body temperature and activity rhythms of male mice

BACKGROUND

Physiological responses to acute ethanol (EtOH) injection depend critically on the timing of their administration. Whether daily timing modulates effects of longer intoxication intervals characteristic of alcohol-dependent humans remains unknown. The present work examines time-of-day effects during EtOH exposure and withdrawal measured by locomotor activity (ActLoc ) and body temperature (Tb ) across multiple rounds of EtOH exposure/withdrawal.

METHODS

Two groups of C57BL/6J mice (n = 8 per group), implanted with radio-telemeters, were entrained to opposite light-dark periods (14:10 LD cycle) so that their rest/activity cycles were 12 hours apart. Under a 2-hour skeleton photoperiod animals were simultaneously exposed to 3 daily cycles of EtOH vapor inhalation (14 hours EtOH on) and withdrawal (10 hours EtOH off). During this time, air-only control groups (n = 4 per group) matched for entrainment were handled in a comparable manner. After the third cycle of EtOH vapor, the animals were left undisturbed for 11 days to recover. The 14-day protocol was repeated 3 additional times.

RESULTS

During intoxication, mice exposed to EtOH in the subjective night exhibited greater hypothermia and more overall disruptions in the Tb and ActLoc rhythms. Acute withdrawal induced hypothermia during the subjective night and hyperthermia during the subjective day. Animals in both phases demonstrated significant disruptions in ActLoc during withdrawal. ActLoc had little effect on Tb during EtOH exposure, but it significantly influenced Tb during acute withdrawal.

CONCLUSIONS

The physiological responses of both EtOH exposure and withdrawal differ as a function of time of day. These findings suggest that controlling for the circadian phase of exposure and/or withdrawal may mitigate the severity of symptomatic withdrawal.

Behavioral characteristics and pharmacological manipulations of a nicotine-entrainable circadian oscillator

Chronic daily administration of nicotine and other drugs of abuse has been found to entrain pre- and post-drug circadian locomotor activity episodes that oscillate on a 24-h schedule and persist for several days after administration ceases. This drug-entrainable oscillator system could conceivably lead to circadian rhythms of drug seeking and drug use in human drug addicts. The present study (1) characterizes the ability of daily nicotine administration to entrain circadian wheel-running activity episodes in rats across a range of doses, lighting schedules, and food access; and (2) tests whether pre- and post-nicotine episodes can be altered through pharmacological manipulations. Adult female rats were housed in wheel boxes for 35-60 d, and both wheel-running and feeding-related behaviors were measured continuously. Following acclimation, nicotine or saline was administered for 16-24 d, and the rats were left undisturbed for several test days to observe the persistence of nicotine-entrained activity. The results showed that nicotine dose-dependently entrains wheel-running activity, and the highest dose of 1.0 mg/kg produces robust pre- and post-nicotine circadian activity episodes under constant, fixed, and variable light/dark schedules. In the pharmacological manipulation experiment, nicotine-entrained rats were administered one of seven pharmacological treatments (varenicline, mecamylamine, acamprosate, topiramate, naltrexone, SB-334867, or bupropion) in place of the nicotine injection for 2 d, and the rats were not disturbed for four subsequent days. Most of the treatment drugs significantly reduced post-nicotine activity episodes, but only three treatments affected pre-nicotine episodes: the μ- and κ-opioid receptor antagonist naltrexone, the orexin-1 receptor antagonist SB-334867, and the AMPA (2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid)/kainate antagonist topiramate. These results show that chronic daily nicotine administration is a robust zeitgeber that dose-dependently entrains a nonphotic oscillator system that includes opioid, orexin, and glutamate pathways.

PER3 polymorphism and insomnia severity in alcohol dependence

STUDY OBJECTIVES

Insomnia is common, persistent, and associated with relapse in alcohol-dependent (AD) patients. Although the underlying mechanisms are mostly unstudied, AD patients have impaired circadian rhythms and sleep drive, which may be genetically influenced. A polymorphism in the PER3 gene (PER3(4/4), PER3(4/5), PER3(5/5)) has previously been associated with circadian preference and sleep homeostasis, and the PER3(4/4)genotype has been characterized by evening preference and decreased sleep drive. The purpose of this study was to examine the influence of this polymorphism on insomnia severity in AD patients. We hypothesized that the PER3 polymorphism would be an independent predictor of insomnia severity with greatest severity observed in those with the PER3(4/4)genotype.

DESIGN

Cross-sectional association of patient characteristics, genotype, and insomnia severity. Significant (P < 0.05) bivariate correlates were further analyzed by hierarchical, forced entry multiple linear regression.

SETTING

Alcohol treatment programs in Warsaw, Poland.

PATIENTS

Diagnosed with alcohol dependence (n = 285), according to the Diagnostic and Statistical Manual of Mental Disorders, 4(th) edition.

MEASUREMENTS AND RESULTS

Drinking frequency, mental and physical health status, childhood abuse, and PER3 genotype were independent predictors of insomnia severity, as measured by a 7-item subscale of the Sleep Disorders Questionnaire, explaining 28.9% of the variance. Addition of the genotype in the final step significantly increased the amount of variance explained by 1.1% (P = 0.027). Those with the PER3(4/4)genotype had the greatest severity of insomnia symptoms.

CONCLUSIONS

PER3 genotype contributed unique variance in predicting insomnia severity in AD patients. These results are consistent with genetically influenced impairment in sleep regulation mechanisms in AD patients with insomnia.

Circadian rhythms, sleep, and substance abuse

Substance abuse is linked to numerous mental and physical health problems, including disturbed sleep. The association between substance use and sleep appears to be bidirectional, in that substance use may directly cause sleep disturbances, and difficulty sleeping may be a risk factor for relapse to substance use. Growing evidence similarly links substance use to disturbances in circadian rhythms, although many gaps in knowledge persist, particularly regarding whether circadian disturbance leads to substance abuse or dependence. Given the integral role circadian rhythms play in regulating sleep, circadian mechanisms may account in part for sleep-substance abuse interactions. Furthermore, a burgeoning research base supports a role for the circadian system in regulating reward processing, indicating that circadian mechanisms may be directly linked to substance abuse independently of sleep pathways. More work in this area is needed, particularly in elucidating how sleep and circadian disturbance may contribute to initiation of, and/or relapse to, substance use. Sleep and circadian-based interventions could play a critical role in the prevention and treatment of substance use disorders.

Ethanol consumption in mice: relationships with circadian period and entrainment

A functional connection between the circadian timing system and alcohol consumption is suggested by multiple lines of converging evidence. Ethanol consumption perturbs physiological rhythms in hormone secretion, sleep, and body temperature; and conversely, genetic and environmental perturbations of the circadian system can alter alcohol intake. A fundamental property of the circadian pacemaker, the endogenous period of its cycle under free-running conditions, was previously shown to differ between selectively bred high- (HAP) and low- (LAP) alcohol preferring replicate 1 mice. To test whether there is a causal relationship between circadian period and ethanol intake, we induced experimental, rather than genetic, variations in free-running period. Male inbred C57Bl/6J mice and replicate 2 male and female HAP2 and LAP2 mice were entrained to light:dark cycles of 26 or 22 h or remained in a standard 24 h cycle. On discontinuation of the light:dark cycle, experimental animals exhibited longer and shorter free-running periods, respectively. Despite robust effects on circadian period and clear circadian rhythms in drinking, these manipulations failed to alter the daily ethanol intake of the inbred strain or selected lines. Likewise, driving the circadian system at long and short periods produced no change in alcohol intake. In contrast with replicate 1 HAP and LAP lines, there was no difference in free-running period between ethanol naïve HAP2 and LAP2 mice. HAP2 mice, however, were significantly more active than LAP2 mice as measured by general home-cage movement and wheel running, a motivated behavior implicating a selection effect on reward systems. Despite a marked circadian regulation of drinking behavior, the free-running and entrained period of the circadian clock does not determine daily ethanol intake.

Neuroimaging insights into the role of cortical GABA systems and the influence of nicotine on the recovery from alcohol dependence

This paper reviews evidence suggesting that nicotine and tobacco smoke profoundly modulate the effects of alcohol on γ-aminobutyric acid (GABA) neuronal function, specifically at the GABA(A)-benzodiazepine receptor (GABA(A)-BZR). The focus of this paper is on recent neuroimaging evidence in preclinical models as well as clinical experiments. First, we review findings implicating the role of alcohol at the GABA(A)-BZR and discuss the changes in GABA(A)-BZR availability during acute and prolonged alcohol withdrawal. Second, we discuss preclinical evidence that suggests nicotine affects GABA neuronal function indirectly by a primary action at neuronal nicotinic acetylcholine receptors. Third, we show how this evidence converges in studies that examine GABA levels and GABA(A)-BZRs in alcohol-dependent smokers and nonsmokers, suggesting that tobacco smoking attenuates the chemical changes that occur during alcohol withdrawal. Based on a comprehensive review of literature, we hypothesize that tobacco smoking minimizes the changes in GABA levels that typically occur during the acute cycles of drinking in alcohol-dependent individuals. Thus, during alcohol withdrawal, the continued tobacco smoking decreases the severity of the withdrawal-related changes in GABA chemistry. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.

Fentanyl, but not haloperidol, entrains persisting circadian activity episodes when administered at 24- and 31-h intervals

Administration of several drugs of abuse on a 24-h schedule has been shown to entrain both pre-drug (anticipatory) and post-drug (evoked) circadian activity episodes that persist for several days when the drug is withheld. The present study tested the entrainment effects of fentanyl, an opioid agonist with a noted abuse liability, and haloperidol, an anti-psychotic dopamine antagonist without apparent abuse liability. Adult female Sprague-Dawley rats housed under constant light in cages with attached running wheels received repeated low, medium, or high doses of either fentanyl or haloperidol on a 24-h administration schedule followed by a 31-h schedule (Experiment 1) or solely on a 31-h schedule (Experiment 2). The results showed that all three doses of fentanyl entrained both pre-drug and post-drug episodes of wheel running when administered every 24h, and the combined pre- and post-fentanyl activity episodes persisted for at least 3 days when the drug was withheld during test days. On the 31-h schedule, fentanyl produced an "ensuing" activity episode approximately 24h post-administration, but failed to produce an anticipatory episode 29-31h post-administration. In contrast, haloperidol injections failed to produce both pre-drug episodes on the 24-h schedule and circadian ensuing episodes on the 31-h schedule, and post-haloperidol suppression of activity appeared to mask the free-running activity rhythm. Taken together, these results provide additional evidence that drugs of abuse share a common ability to entrain circadian activity episodes.

Circadian timing of ethanol exposure exerts enduring effects on subsequent ad libitum consumption in C57 mice

BACKGROUND

There is a daily rhythm in the voluntary intake of ethanol in mice, with greatest consumption in the early night and lowest intake during the day. The role of daily timing of ethanol exposure on the development and control of long-term ethanol self-administration has been neglected. The present study examines these issues using C57BL/6J mice.

METHODS

Mice were repeatedly exposed to 10% ethanol for 2 hours early in the night or day for several weeks. Subsequently, ethanol was available at the opposite time (Expt 1) or 24 hours daily (Expts 1 and 2). Lick sensors recorded the patterns of drinking activity in Experiment 2.

RESULTS

Mice exposed to ethanol during the night drink more than mice exposed during the day. Prior history did not affect ethanol intake when the schedule was reversed. Under 24-hour exposure conditions, mice with a history of drinking during the night consumed significantly more than mice drinking during the day. The circadian patterns of drinking were not altered.

CONCLUSIONS

These results demonstrate that the daily timing of ethanol exposure exerts enduring effects of self-administration of ethanol in mice. Understanding how circadian rhythms regulate ethanol consumption may be valuable for modifying subsequent intake.

A randomized double-blind pilot trial of gabapentin versus placebo to treat alcohol dependence and comorbid insomnia

BACKGROUND

Insomnia and other sleep disturbances are common, persistent, and associated with relapse in alcohol-dependent patients. The purpose of this pilot study was to compare gabapentin versus placebo for the treatment of insomnia and prevention of relapse in alcohol-dependent patients.

METHODS

Twenty-one subjects, including 10 women who met study criteria for alcohol dependence and insomnia and expressed a desire to abstain from alcohol, were recruited to the study. During a 1 to 2 week placebo lead-in and screening phase, a complete medical history, physical exam, blood tests, urine drug test, and structured interviews were performed to determine eligibility and patterns of alcohol use and sleep. Insomnia due to intoxication or acute withdrawal, psychiatric or medical illness, medications, and other sleep disorders were ruled out. Subjects were then randomized to either placebo (n = 11) or gabapentin (n = 10) for 6 weeks and titrated over a 10-day period to 1,500 mg or 5 pills at bedtime. After a 4-day taper, subjects were reassessed 6 weeks after ending treatment.

RESULTS

Gabapentin significantly delayed the onset to heavy drinking, an effect which persisted for 6 weeks after treatment ended. Insomnia improved in both treatment groups during the medication phase, but gabapentin had no differential effects on sleep as measured by either subjective report or polysomnography.

CONCLUSION

Because gabapentin is a short-acting medication that was taken only at nighttime in this study, it may possibly exert a nocturnal effect that prevents relapse to heavy drinking by a physiological mechanism not measured in this pilot study.

Circadian phenotype in patients with the co-morbid alcohol use and bipolar disorders

AIMS

Alcohol misuse is associated with bipolar disorder. Abnormalities in the circadian clockwork play a role in the pathogenesis of bipolar disorder. Alcohol intake is likely to affect the circadian phenotype. We aimed at analysing the behavioural trait of the preference to morning or evening hours for the daily activities in bipolar disorder patients with or without the co-morbid alcohol use.

METHODS

Our nationwide sample of families included patients with bipolar disorder born during 1940-1969 having at least one hospitalization due to bipolar disorder during 1969-1991 and their first-degree relatives. All the 148 participants were interviewed using the Structured Clinical Interview for DSM-IV Axis I Disorders and assessed using the Morningness-Eveningness Questionnaire whose factor matrix applying for the maximum likelihood principle was calculated for the first time.

RESULTS

Patients with the co-morbid alcohol use disorder were more of the morning type as compared with patients with bipolar disorder only.

CONCLUSIONS

Co-morbid patients preferred more the morning hours for their daily activities, indicative of alcohol consumption having an effect on the circadian clock.

Biological clocks and the practice of psychiatry

Endogenous biological clocks enable living species to acquire some independence in relation to time. They improve the efficiency of biological systems, by allowing them to anticipate future constraints on major physyological systems and cell energy metabolism. The temporal organization of a giwen biological function can be impaired in its coordination with astronomical time or with other biological function. There are also external conditions that influence biological clocks. This temporal organization is complex, and it is possible that a series of psychiatric disorders and syndromes involve primary or secondary changes in biological clocks: seasonal and other mood disorders, premenstrual syndromes, social jet lag, free-running rhythms, and several sleep disorders are among them. In this review, we describe the main concepts relevant to chronobiology and explore the relevance of knowledge about biological clocks to the clinical practice of psychiatry

Chronobiology of alcohol: from chronokinetics to alcohol-related alterations of the circadian system

The development of concepts in chronobiology is intimately linked to studies on alcohol, as a number of these are based on chronobiological variations observed in the metabolism of ethanol. This concerns circadian differences in its metabolism (chronokinetics) and effects (chronoefficacy and chronotoxicity) and also inherent circadian rhythmicity in the sensitivity of target organs to its effects (chronesthesy). Chronobiologic discoveries are also fertile grounds for understanding the biological and psychotropic effects of alcohol. Confusing effects, which are difficult to explain by conventional homeostatic theory, are easy to understand when considered in the context of the concepts of chronopharmacology, and thereby uncovering new pathways of investigation. Beyond the studies that have elucidated the rhythm-dependent variation in ethanol, chronobiology is opening new explanatory pathways concerning the attributes of the alcohol withdrawal syndrome and effects of alcohol on the development of the central nervous system, particularly the development of the internal clock, and on the alcohol-dependency syndrome. The concepts of chronopharmacology and chronotoxicology are of equal importance to the fields of occupational medicine and industry medicine.