Chronobiological regulation of alcohol intake

Abstract

Like other physiological functions, food intake and metabolism (including alcohol consumption) in humans and animal models may be regulated by circadian rhythm. For example, many studies of rodents have found that alcohol consumption in these nocturnal animals peaks during their active dark period. This alcohol consumption pattern can be influenced, however, by experimental manipulation. One factor that has been proposed to play a role in regulating circadian alcohol consumption pattern is the hormone melatonin, which is produced by the pineal gland. Research also indicates that the effects of lighting conditions on the alcohol consumption of animal models may be influenced by the differences among the strains of the laboratory animals used, variations in the type and administration schedule of the animals' alcohol-containing diet, disruptions of the normal circadian rhythm, concurrent use of other drugs, and properties of the light.

Figure 1

Alcohol consumption patterns of two mouse strains (CBA and TO) that received alcohol either in a liquid diet containing 7-percent alcohol that constituted the animals’ sole source of food or as an alcohol solution in addition to regular laboratory food. When the alcohol was provided in the form of a liquid diet (circles), the alcohol consumption patterns (and thus the blood alcohol concentrations [BACs]) of the two mouse strains differed considerably. In the CBA mice (A), BACs peaked around 7 p.m. and remained high throughout the night. Conversely, the BACs in TO mice (B) showed a sharp peak around 9 a.m. When the alcohol was provided in the form of a solution containing 10 percent (empty squares) or 20 percent (half-empty squares) alcohol, however, alcohol consumption and BACs in both strains were considerably reduced and distributed more evenly throughout the day. Furthermore, no substantial differences existed in the alcohol consumption patterns of the two strains under these conditions. (Error bars are not shown.) mM = millimolar. SOURCE: Jelic et al. 1998.

Figure 2

Alcohol consumption patterns of rats receiving drinking water containing (A) 2 percent, (B) 6 percent, or (C) 10 percent alcohol. The animals had access to the alcohol solution for 23 hours per day. Both overall fluid consumption and circadian consumption patterns differed depending on the alcohol concentration in the drinking water. The horizontal dark line indicates the dark period in the animals’ light-dark cycle. (Error bars are not shown.) mL= milliliter. SOURCE: Boyle et al. 1997.