Effects of ethanol inhalation on EEG in rats

Mechanisms underlying sleep-wake disturbances in alcoholism: focus on the cholinergic pedunculopontine tegmentum

Sleep-wake (S-W) disturbances are frequently associated with alcohol use disorders (AUD), occurring during periods of active drinking, withdrawal, and abstinence. These S-W disturbances can persist after months or even years of abstinence, suggesting that chronic alcohol consumption may have enduring negative effects on both homeostatic and circadian sleep processes. It is now generally accepted that S-W disturbances in alcohol-dependent individuals are a significant cause of relapse in drinking. Although significant progress has been made in identifying the socio-economic burden and health risks of alcohol addiction, the underlying neurobiological mechanisms that lead to S-W disorders in AUD are poorly understood. Marked progress has been made in understanding the basic neurobiological mechanisms of how different sleep stages are normally regulated. This review article in seeking to explain the neurobiological mechanisms underlying S-W disturbances associated with AUD, describes an evidence-based, easily testable, novel hypothesis that chronic alcohol consumption induces neuroadaptive changes in the cholinergic cell compartment of the pedunculopontine tegmentum (CCC-PPT). These changes include increases in N-methyl-d-aspartate (NMDA) and kainate receptor sensitivity and a decrease in gamma-aminobutyric acid (GABAB)-receptor sensitivity in the CCC-PPT. Together these changes are the primary pathophysiological mechanisms that underlie S-W disturbances in AUD. This review is targeted for both basic neuroscientists in alcohol addiction research and clinicians who are in search of new and more effective therapeutic interventions to treat and/or eliminate sleep disorders associated with AUD.

Effects of chronic ethanol exposure on sleep in rats

Sleep disturbance is a common complaint in alcoholics. When polysomnographic studies are performed in alcoholics, reductions in slow wave sleep are a common finding; however, few studies have evaluated the effects of chronic alcohol exposure on sleep in animal models. In the present study, the sleep EEG was evaluated in 40 Wistar rats who were exposed to chronic alcohol or control conditions in vapor chambers. Rats were exposed to ethanol vapors or control chambers for 6 weeks and then withdrawn. Sleep EEG was recorded before exposure (baseline), immediately following exposure, and 5 weeks after withdrawal from the ethanol/control chambers. In the ethanol-exposed animals, blood ethanol levels averaged 192 mg/dL over 6 weeks of exposure. Chronic ethanol exposure and withdrawal was not found to affect either slow wave sleep latency or slow wave sleep duration; however, overall spectral power as well as power in the delta, theta, and beta frequencies were significantly reduced following chronic exposure (2-4 Hz, [F(1, 17) = 18.11, p = 0.001], 4-6 Hz, [F(1, 17) = 15.98, p = 0.001], 6-8 Hz [F(1, 17) = 15.52, p = 0.001], 8-16 Hz band [F(1, 17) = 18.73, p < 0.0001], 16-32 Hz [F(1, 17) = 10.13, p = 0.005], and 1-50 Hz [F(1, 17) = 17.03, p = 0.001]. After 5 weeks of withdrawal, significant decreases still persisted in the delta and theta frequencies (2-4 Hz [F(1, 16) = 6.21, 0.024], 4-6 Hz [F(1, 16) = 6.26, 0.024], and 6-8 Hz [F(1, 16) = 4.84, p = 0.043]). These findings suggest that spectral analysis of the EEG is a highly sensitive measure of the effects of ethanol on sleep. These findings additionally demonstrate that chronic ethanol exposure can produce persistent diminution in the systems that generate cortical slow waves in the rat and thus may provide a model for understanding the mechanisms underlying sleep disturbances associated with alcoholism.

The contribution of electrophysiology to knowledge of the acute and chronic effects of ethanol

This review describes the effects of ethanol on the components of neuronal transmission and the relationship of such effects to the behavioural actions of ethanol. The concentrations of ethanol with acute actions on voltage-sensitive ion channels are first described, then the actions of ethanol on ligand-gated ion channels, including those controlled by cholinergic receptors, 5-hydroxytryptamine receptors, the various excitatory amino acid receptors, and gamma-aminobutyric acid receptors. Acute effects of ethanol are then described on brain areas thought to be involved in arousal and attention, the reinforcing effects of ethanol, the production of euphoria, the actions of ethanol on motor control, and the amnesic effects of ethanol; the acute effects of ethanol demonstrated by EEG studies are also discussed. Chronic effects of alcohol on neuronal transmission are described in the context of the various components of the ethanol withdrawal syndrome, withdrawal hyperexcitability, dysphoria and anhedonia, withdrawal anxiety, craving, and relapse drinking. Electrophysiological studies on the genetic influences on the effects of ethanol are discussed, particularly the acute actions of ethanol and electrophysiological differences reported in individuals predisposed to alcoholism. The conclusion notes the concentration of studies on the classical transmitters, with relative neglect of the effects of ethanol on peptides and on neuronal interactions between brain areas and integrated patterns of neuronal activity.

Pharmacology of ethanol and glutamate antagonists on rodent sleep: a comparative study

Twenty-five Sprague-Dawley rats were implanted with electrodes for standard sleep-wake cycle recordings. A guide cannula was stereotaxically implanted into the lateral ventricle. Rats were divided into five groups (n = 5) and challenged with an intraventricular administration of 10 microliters of a 5 nM solution of either: ethanol (EtOH), MK-801, AP5 (noncompetitive and competitive NMDA receptor antagonists, respectively), CNQX (AMPA receptor antagonist), or saline. Rats were recorded polygraphically for the following 4 h. Results showed that, at comparable doses, all tested drugs reduced REM sleep. No significant changes were detected in slow-wave sleep or wakefulness. This selective effect of glutamatergic antagonists suggests that glutamate may be a selective modulator of REM sleep. These findings also show that EtOH shares similar pharmacological effects on the sleep-wake cycle of the rat. Ultimately, glutamatergic mechanisms could contribute to the EtOH-mediated reduction of REM sleep.

Behavioral effects of ethanol inhalation in rats

Behavioral effects of ethanol inhalation were studied on two fixed-ratio (FR) liquid-reinforced schedules and a continuous reinforcement (CRF) schedule intracranial self-stimulation (SS) in rats using the inhalational behavioral chamber designed in our laboratory. In the FR-24 schedule ethanol caused a decrease of reinforcement rate at 161 ppm and higher concentrations. In the FR-50 schedule decreases of the rate were observed at 102 ppm and 203 ppm. In the SS behavior ethanol produced a decrease in the rate of reinforcement at 603 ppm and higher concentrations. In rats of this schedule, blood ethanol concentrations were measured to be 393 micrograms/ml and 545 micrograms/ml after exposure to 600 ppm and 1200 ppm of ethanol respectively. Acute tolerance to ethanol was observed in these experiments, particularly in the FR-24 schedule. Thus ethanol inhalation could produce adequate blood concentrations so as to produce behavioral effects.