Pineal gland and melatonin influence on chronic alcohol consumption by hamsters

Male golden hamsters preferentially consume alcohol solution when given a free-choice between water and the alcohol solution. The pineal gland has been implicated as influencing the predilection for the ethanol solution. Melatonin, a pineal hormone, was administered either daily for 11 weeks as a subcutaneous injection (25 micrograms/animal) or weekly as a subcutaneous beeswax implant (1 mg melatonin/24 mg beeswax) for 5 weeks to hamsters allowed a free-choice between water or a 10% ethanol solution. Food, water and alcohol consumptions were measured on a daily basis. Animals treated by daily injection with melatonin consumed slightly less ethanol than animals not given melatonin. In light-deprived animals given chronic implants of melatonin, alcohol consumption was reduced when compared to alcohol consumption by light-deprived hamsters not receiving melatonin. Melatonin treatment also resulted in reducing daily total fluid intake as well as ethanol consumption in light-deprived hamsters. The results indicate that the pineal gland may influence fluid consumption in the hamster, and indirectly alters the propensity of the hamster to consume alcohol.