Alcohol, alcoholism, and biological rhythms

Photoperiodic modulation of voluntary ethanol intake in C57BL/6 mice

Seasonal and geographic variations in light exposure influence human mood and behavior, including alcohol consumption. Similarly, manipulation of the environmental lighting regimen modulates voluntary ethanol intake in experimental animals. Nevertheless, previous studies in rats and hamsters have been somewhat inconsistent, and little is known concerning such effects in mice. In the present study, we maintained male C57Bl/6 mice in running-wheel cages under either short- or long-photoperiod light-dark cycles (LD 6:18 vs. LD 18:6); subsequently, the same animals were maintained under short or long "skeleton photoperiods", consisting of two daily 15-min light pulses signaling dusk and dawn (SP 6:18 vs. SP 18:6). Running wheels were locked mechanically for half the animals under each photoperiod. Analysis of running wheel patterns showed that mice displayed stable circadian adaptation to both standard LD cycles and skeleton photoperiods. Mice consumed more ethanol and less water, and thus showed higher ethanol preference, under LD 6:18 and SP 6:18 relative to the corresponding long-photoperiod regimens. While running-wheel access increased water intake, ethanol intake was unaffected by this manipulation. These effects are consistent with previous studies showing that short photoperiods or constant darkness increases ethanol intake in rodents. Further, the similarity of the effects of complete and skeleton photoperiods suggests that these effects are mediated by photoperiod-induced alterations in the circadian entrainment pattern, rather than by light exposure per se.

Effects of repeated light-dark phase shifts on voluntary ethanol and water intake in male and female Fischer and Lewis rats

Several lines of evidence implicate reciprocal interactions between excessive alcohol (ethanol) intake and dysregulation of circadian biological rhythms. Thus, chronic alcohol intake leads to widespread circadian disruption in both humans and experimental animals, while in turn, chronobiological disruption has been hypothesized to promote or sustain excessive alcohol intake. Nevertheless, the effects of circadian disruption on voluntary ethanol intake have not been investigated extensively, and prior studies have reported both increased and decreased ethanol intake in rats maintained under "shift-lag" lighting regimens mimicking those experienced by shift workers and transmeridian travelers. In the present study, male and female inbred Fischer and Lewis rats were housed in running wheel cages with continuous free-choice access to both water and 10% (vol/vol) ethanol solution and exposed to repeated 6-h phase advances of the daily light-dark (LD) cycle, whereas controls were kept under standard LD 12:12 conditions. Shift-lag lighting reduced overall ethanol and water intake, and reduced ethanol preference in Fischer rats. Although contrary to the hypothesis that circadian disruption would increase voluntary ethanol intake, these results are consistent with our previous report of reduced ethanol intake in selectively bred high-alcohol-drinking (HAD1) rats housed under a similar lighting regimen. We conclude that chronic circadian disruption is a form of chronobiological stressor that, like other stressors, can either increase or decrease ethanol intake, depending on a variety of poorly understood variables.

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.

Acute ethanol impairs photic and nonphotic circadian phase resetting in the Syrian hamster

Disrupted circadian rhythmicity is associated with ethanol (EtOH) abuse, yet little is known about how EtOH affects the mammalian circadian clock of the suprachiasmatic nucleus (SCN). Clock timing is regulated by photic and nonphotic inputs to the SCN involving glutamate release from the retinohypothalamic tract and serotonin (5-HT) from the midbrain raphe, respectively. Our recent in vitro studies in the SCN slice revealed that EtOH blocks photic phase-resetting action of glutamate and enhances the nonphotic phase-resetting action of the 5-HT1A,7 agonist, 8-OH-DPAT. To explore the basis of these effects in the whole animal, we used microdialysis to characterize the pharmacokinetics of intraperitoneal injection of EtOH in the hamster SCN extracellular fluid compartment and then studied the effects of such EtOH treatment on photic and serotonergic phase resetting of the circadian locomotor activity rhythm. Peak EtOH levels (approximately 50 mM) from a 2 g/kg injection occurred within 20-40 min with a half-life of approximately 3 h. EtOH treatment dose-dependently attenuated photic phase advances but had no effect on phase delays and, contrary to in vitro findings, markedly attenuated 8-OH-DPAT-induced phase advances. In a complementary experiment using reverse microdialysis to deliver a timed SCN perfusion of EtOH during a phase-advancing light pulse, the phase advances were blocked, similar to systemic EtOH treatment. These results are evidence that acute EtOH significantly affects photic and nonphotic phase-resetting responses critical to circadian clock regulation. Notably, EtOH inhibition of photic signaling is manifest through direct action in the SCN. Such actions could underlie the disruption of circadian rhythmicity associated with alcohol abuse.

Repeated light-dark phase shifts modulate voluntary ethanol intake in male and female high alcohol-drinking (HAD1) rats

BACKGROUND

Chronic disruption of sleep and other circadian biological rhythms, such as occurs in shift work or in frequent transmeridian travel, appears to represent a significant source of allostatic load, leading to the emergence of stress-related physical and psychological illness. Recent animal experiments have shown that these negative health effects may be effectively modeled by exposure to repeated phase shifts of the daily light-dark (LD) cycle. As chronobiological disturbances are thought to promote relapse in abstinent alcoholics, and may also be associated with increased risk of subsequent alcohol abuse in nonalcoholic populations, the present experiment was designed to examine the effects of repeated LD phase shifts on voluntary ethanol intake in rats. A selectively bred, high alcohol-drinking (HAD1) rat line was utilized to increase the likelihood of excessive alcoholic-like drinking.

METHODS

Male and female rats of the selectively bred HAD1 rat line were maintained individually under a LD 12:12 cycle with both ethanol (10% v/v) and water available continuously. Animals in the experimental group were subjected to repeated 6-hour LD phase advances at 3 to 4 week intervals, while control rats were maintained under a stable LD cycle throughout the study. Contact-sensing drinkometers were used to monitor circadian lick patterns, and ethanol and water intakes were recorded weekly.

RESULTS

Control males showed progressively increasing ethanol intake and ethanol preference over the course of the study, but males exposed to chronic LD phase shifts exhibited gradual decreases in ethanol drinking. In contrast, control females displayed decreasing ethanol intake and ethanol preference over the course of the experiment, while females exposed to experimental LD phase shifts exhibited a slight increase in ethanol drinking.

CONCLUSIONS

Chronic circadian desynchrony induced by repeated LD phase shifts resulted in sex-specific modulation of voluntary ethanol intake, reducing ethanol intake in males while slightly increasing intake in females. While partially contrary to initial predictions, these results are consistent with extensive prior research showing that chronic stress may either increase or decrease ethanol intake, depending on strain, sex, stressor type, and experimental history. Thus, repeated LD phase shifts may provide a novel chronobiological model for the analysis of stress effects on alcohol intake.

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

Loss of control over drinking and the craving for alcohol are cardinal signs of alcohol dependence. Our clinical practice indicates that these cravings do not occur randomly during the day, but at the same times each day for the same patient. To validate this hypothesis that alcohol-dependent patients have a circadian rhythmic craving in their desire for their first drink of the day, we asked 217 persons diagnosed as alcohol-dependent according to DSM-IV criteria to complete a questionnaire that surveyed whether this craving occurred at a fixed time each day. Of the respondents, 82% reported it did; 87% of them could state the time of day they consumed their first daily drink; and 80% reported that the time of their first drink of the day did not vary much from one day to the next. The most frequent time of consuming the first drink of alcohol was between 09:00 and 11:00 h, and it was independent of the subjects' sleep-wake routine (the delay between the hours of wake-up and the time of the first urge for alcohol was 3:45 +/- 3:30 h) and lunch or dinner time. This rhythmicity seems to be a pertinent criterion for alcohol dependence syndrome.

[Alcohol, chronobiology and sleep]

Chronobiology is the scientific discipline of biologic rhythm study. Applications of the emerging concepts of chronobiology are now use in several fields of clinical medicine. Alcohol related disorders seems to be clarified with the main concepts of chronobiology. Thus chronopharmacology (specially chronokinetics and time-related differences in drug effects) clears up variations of blood alcohol levels and toxicity of ethanol during the 24 h, chronesthesy explains the action of ethanol on biological rhythms of hormone secretions and sleep, and the concept of chronopathology seems to be apply to alcohol dependence. We review in this article some applications in alcohol related disorders of the main concepts of chronobiology.

Characterization of cocaine self-administration and pharmacokinetics as a function of time of day in the rat

Two experiments examined the influence of time of day on the intravenous self-administration of cocaine and its associated pharmacokinetic profile in male Sprague-Dawley rats. In both experiments, individual rats were randomly assigned to experimental groups (n = 6/group) according to four selected times of day, 0100, 0700, 1300, and 1900 h, during which experimental procedures were conducted. In both experiments, rats were maintained under a 12 L:12 D ambient lighting cycle, with lights on at 0600 h. Training and testing was thus conducted either 1 (0700, 1900) or 7 (1300, 0100 h) hours into the light and dark phases. In Experiment 1, characteristics of cocaine self-administration across a behaviorally active dose range were assessed. Statistically significant differences were observed in the rates and patterns of self-administration across the four experimental groups, most notably characterized by an apparent shift in the dose of cocaine, which engendered peak rates of responding. Specifically, groups tested at 0100 and 1300 h appeared to exhibit enhanced sensitivity to the reinforcing properties of low-dose cocaine relative to groups tested at 0700 and 1900 h. The observed differences in apparent sensitivity of experimental subjects to low-dose cocaine were not related in any simple way to ongoing patterns of general locomotor activity, and were not accompanied by corresponding variance in the pharmacokinetic profiles of cocaine when assessed over 1 h following an intravenous infusion (1.8 mg/kg) at each of the four sampling periods noted above.

Effects of alcohol on the synthesis and expression of hypothalamic peptides

Studies aimed at analyzing the deleterious effects of excess alcohol in the brain have revealed structural alterations that are often associated with functional and behavioral disturbances. Among the neuronal damage related to prolonged alcohol exposure, alterations in the synthesizing capabilities and levels of expression of neuroactive peptides have been increasingly reported. Actually, such changes frequently represent the sole repercussion of acute and short-term exposure to ethanol. This review gathers the existing data on the effects of ethanol exposure on the synthesis and expression of hypothalamic peptides. Amid those that can act both as neurotransmitters and neurohormones, we allude to vasopressin, corticotropin-releasing hormone, thyrotropin-releasing hormone and pro-opiomelanocortin and related peptides produced by paraventricular, supraoptic and arcuate neurons. With respect to peptides that act exclusively as neurotransmitters, we address the effects of alcohol on vasoactive intestinal polypeptide, gastrin-releasing peptide, somatostatin and vasopressin synthesized by suprachiasmatic neurons. Hypothalamic neurons that produce peptides that act as neurotransmitters are supposed to be modulated primarily by influences exerted by neuronal afferents, whereas those producing peptides that additionally act as neurohormones are also regulated by peripheral stimuli (e.g., plasma levels of circulating hormones, osmotic challenges). These peculiar features endue the hypothalamus with characteristics that are particularly propitious to enlighten the still cryptic mechanisms underlying the ethanol effects on protein synthesis.

Circadian variations in plasma monoamine metabolites level in alcoholic patients: a possible predictor of alcohol withdrawal delirium

1. Alcohol withdrawal symptoms in 17 alcoholics were classified into two groups according to the severity of their symptoms, and circadian variations in their plasma 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA) levels during the alcohol withdrawal and the abstention periods were compared with those in normal controls by two-way ANOVA. 2. Circadian variations in plasma 5HIAA level in alcoholic patients manifested severe alcohol withdrawal symptoms and exhibited phase advances in both the withdrawal and the abstention periods and significantly higher levels in the abstention period. 3. Circadian variation in plasma HVA in the abstention period in alcoholics showed severe withdrawal symptoms demonstrating significantly higher levels compared with normal controls. 4. These findings suggest that the serotonergic and dopaminergic activity may vary depending on the severity of alcohol withdrawal symptoms and the measurement of circadian variations in plasma 5HIAA and HVA levels could possibly be used as a predictor of hardly predictable alcohol withdrawal delirium.

Circadian variation in plasma 5-hydroxyindoleacetic acid level during and after alcohol withdrawal: phase advances in alcoholic patients compared with normal subjects

Alcohol withdrawal symptoms in 19 male alcoholics were objectively evaluated and classified and circadian variation in their plasma 5-hydroxyindoleacetic acid (5-HIAA) concentrations was determined at 3 different intervals after cessation of drinking. Circadian variations in plasma 5-HIAA level exhibited phase advances in alcoholic patients compared with normal controls and were different depending on the severity of alcohol withdrawal symptoms. Plasma 5-HIAA in patients with delirium tremens showed significantly higher levels during the abstention period, possibly suggesting peculiarity in their serotonergic metabolism.

The rate of ethanol absorption is influenced by corticosterone in long-sleep and short-sleep mice

Ethanol was administered by intragastric (IG) injection and absorption was measured in long-sleep (LS) and short-sleep (SS) mice under various conditions that alter levels of adrenal steroids. In naive mice, LS mice absorbed ethanol more quickly than SS mice. Ethanol absorption was slower in both lines of mice after adrenalectomy (ADX). Short-term inhibition of corticosterone synthesis had no effect on ethanol absorption in either line of mice. The effect of ADX was most pronounced in SS mice at 24 hr after surgery and at 168 hr after surgery in LS mice. Therefore, the effects of various steroid replacements were examined at these times. At 24 hr after ADX, ethanol absorption was replaced to SHAM-operated values in SS mice receiving corticosterone treatments. Likewise, in LS mice at 168 hr after ADX, corticosterone implants reversed the effects of ADX while dexamethasome was ineffective. These results support a role for corticosterone in regulation of gastric ethanol absorption and suggest that the lack of repeatability for pharmacokinetic measures of ethanol absorption and metabolism in previous human and animal studies may relate to environmental impact on stress responses.

Urine melatonin in alcoholic patients: a marker of alcohol abuse?

Ethanol is known to alter central neurotransmission and endocrine functions. Urine melatonin was studied in 10 male chronic alcoholic patients, before and after two weeks of controlled alcohol abstinence, and in sex and age matched healthy controls. In both groups, 24-hour urines were collected in two fractions corresponding to day- (D) (08:00-20:00) and night- (N) (20:00-08:00) time. Urine melatonin was assayed by RIA after methylene chloride extraction. Twenty-four hour urine melatonin levels were calculated adding up D and N values. In patients during alcohol intake, the 24-hour urine melatonin levels were significantly higher than in controls (p = 0.004, Student's t test). A disruption of the physiological ratio between N and D values was also observed, since the higher melatonin levels occurred in the D fraction. In drinking alcoholics, melatonin D values were significantly higher than the D values found in controls (p less than 0.01, Student's t test) and in the same patients after alcohol withdrawal (p less than 0.05). The N/D ratio approximated 1 during alcohol intake and became larger than 1 after alcohol withdrawal, as in the controls. The melatonin data were correlated with the suppressive effects of dexamethasone (DXT) on cortisol secretion evaluated both during alcohol intake and during abstinence. After alcohol withdrawal, the two (out of 10) patients, who remained unresponsive to the DXT suppression test, showed high D melatonin values and a low N/D ratio. These preliminary data indicate that in chronic alcoholism the pattern of urinary "melatonin- like immunoreactivity" is altered.

Stress and alcohol interaction: an update of human research

The literature on alcohol and stress in human subjects carried out since 1981 is reviewed. The review covers selected aspects of the interaction of alcohol and stress. (1) Most of the review focuses on the role of stress on alcohol ingestion. Retrospective research based on data from the Health and Nutrition Examination Survey indicated an increase in alcohol consumption with anxiety in certain groups of, as yet not well characterized, individuals. For example, although still insufficiently documented, stress does not appear to play a significant role in alcohol ingestion by women and the elderly. By contrast, stress does appear to play a role in the control of alcohol ingestion by adolescents. Prospective studies employing questionnaire-interview formats generally support an effect of stress on alcohol ingestion. However, studies employing male college aged social drinkers did not find a correlation between levels of stress and ingestion of alcohol. Alcoholics also differ in the reasons for drinking alcohol, but generally ingest alcohol to lessen anxiety/stress. It is clear that the Tension Reduction Hypothesis as originally postulated is no longer adequate. Many new models based on an interaction of alcohol and stress have been proposed to explain the control of alcohol consumption. Considering the multidimensionality of factors that appear to contribute to the control of alcohol ingestion, it is unlikely that a single model could possibly be relevant to alcohol ingestion under all conditions. More likely different models may be relevant to alcohol consumption under specific conditions, or for specific populations. (2) Alcohol has been reported to decrease anxiety in agoraphobics. The self-medication by agoraphobics may contribute significantly to their alcohol abuse. (3) Alcohol has also been reported to decrease tremor of the hands in stressed subjects as well as in patients with essential tremor. (4) Although a number of studies have employed electrodermal activity in studies aimed at the interaction of alcohol and stress, the results have been rather inconsistent. (5) The controversy on the purported beneficial effect of alcohol on the cardiovascular system persists. A number of studies have shown a J- or U-shaped relationship between alcohol ingestion and incidence of coronary heart disease. Alcohol may also influence stress-induced changes in blood pressure. Although a number of studies have demonstrated lower blood pressure in individuals ingesting less than two drinks per day compared with abstainers or heavy alcohol imbibers, the evidence is not conclusive. (6) It is not clear whether the interaction of alcohol and stress involves alterations in plasma catecholamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronobiological susceptibility to alcoholism: a hypothesis

The search for carriers of a specific biologic risk for alcoholism is ongoing. In addition to seeking "the needle in the haystack," the need to monitor a broader phenotypic indicator such as chronobiological interaction is hypothesized. Certain potential mediators of genetic predisposition to alcoholism are subject to periodic rhythmicity in both animal and human investigations. These mediators include prolactin, cortisol, and MOPEG levels along with possible sleep characteristics. Suggestions for future animal and human investigations are outlined using adequate sampling criteria, appropriate rating and recording instruments, and controls predisposed to other psychiatric diagnoses.