[Alcohol, chronobiology and sleep]

Morphologic variations in the pineal gland of the albino rat after a chronic alcoholisation process

We studied the effect of alcohol on the pineal gland of 48 male Wistar rats. Animals were divided into control and experimental groups. The experimental group underwent a previous progressive alcoholisation period with ethanol diluted in water at a concentration of 40%. Animals were sacrificed at 3, 6, 9 and 12 months, and the ultrastructure, karyometric indices, and number of synaptic bodies in the pineal gland were analysed. The results showed progressive morphologic alterations in the ethanol-treated animals, which culminated in fatty degeneration of the pineal parenchyma after 6 months. The karyometric indices decreased in both the central and peripheral areas compared with the control group. Moreover, the seasonal rhythmicity observed in the controls disappeared in the experimental groups, whose number of different populations of synaptic bodies (synaptic ribbons and synaptic spherules) considerably lowered with inversion of their normal seasonal rhythm. These results support that chronic alcoholisation leads to fatty degeneration of the pineal parenchyma, and a considerable alteration in nuclear functional rhythms and synaptic bodies.

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.