Development of tolerance to ethanol in the sleep-wakefulness cycle

Abstract

The development of tolerance to drugs is a primary stage from neuroadapation to neurodegeneration. This applies to alcohol, which due to its complex impact on the nervous system and easily accessible, is the widespread psychotropic substance. Tolerance to alcohol can take place in many behavioral tests. However, the structure of the sleep-wakefulness cycle (SWC) is not taken into account, despite the fact that the structure of the SWC is sensitive to a variety of actions (pharmacological and non-pharmacological) and, can be considered as valid model to study them, including ethanol administration. Therefore the question whether tolerance to ethanol might be reflected in changes of the structure of SWC is relevant in the sense that these alterations might be primary risk- indicators at alcohol consumption. Reasoning from the above mentioned, the purpose of the present work was to study the effects of tolerance to ethanol on the SWC structure. Experiments were carried out on the adult cats (n = 5). The following methods were used: the stereotaxic; polysomnographic. Alcoholization (0.2–2.5 g/kg 25% ethanol solution) was conducted by i/p injections, that lasted for two weeks. The obtained results were processed statistically and significance of the changes was determined by the Student t-test. Low single doses of ethanol (0.2–0.5 g/kg) did not induce any significant changes in the structure of the SWC. While using doses of 0.6 g/kg it was noted only increasing of the latent period of the onset of sleep. However, the structure of the SWC recovered within 1–2 h after injection. Increasing the dose to 1 g/kg caused severe intoxication, which reflected in a behavioral (anxiety, tremor, vocalizations) and autonomic (vomiting and frequent urination) disorders. Against the background of restless behavioral wakefulness recurrent synchronization, that is the EEG correlate of light slow-wave sleep, developed. The total volume of deep slow-wave sleep was significantly decreased and the latent period of the onset of paradoxical sleep was increased. The structure of sleep was fragmented, coursed by frequent awakenings. For the fifth-eighth day of alcoholization the structure of the SWC restored, behavioral and vegetative signs of intoxication moved out. The obtained results signify that development of tolerance to ethanol can be reflected in the alteration of the structure of SWC.