Tordoff, M.G., and Bachmanov, A.A. Mouse taste preference tests: Why only two bottles? Chemical Senses, 28: 315-324, 2003.

Two-bottle tests have been used extensively to measure the preference for taste and nutrient solutions but there has been little work with tests involving more than two bottles. Here, we compare the results obtained in two-bottle tests with those obtained in three- and six-bottle tests. In Experiment 1, we measured the preferences for 2 mM saccharin, 50 mM citric acid, 0.3 mM quinine hydrochloride and 75 mM NaCl displayed by 129X1/SvJ (129) and C57BL/6J (B6) mice. When mice received three bottles, two providing a taste solution and one providing water, they drank more of the taste solution than when they received a standard two-bottle test, or two spouts providing water and one providing taste solution. The three-bottle tests also revealed the left spout side preferences of the 129 strain and were generally better at distinguishing between the 129 and B6 strains (i.e., were more sensitive) than were two-bottle tests. In Experiment 2, we measured intakes and preferences in tests with 6 bottles, with 1, 2, 3, 4, or 5 containing 75 mM NaCl and the rest containing water. NaCl preferences were monotonically related to the number of NaCl spouts available. A follow-up experiment found similar results whether the index of ingestion was volume intakes or licks. This argues that spillage cannot account for the effect of spout number on taste solution intake. Together, the results suggest that (a) the number of bottles of taste solution and water has a profound influence on taste solution intake and preference, and (b) three-bottle tests may be more sensitive than two-bottle tests in many circumstances.

The work in this paper led us to expand our investigations to examine other situations involving access to multiple sources of nutrients. Two papers are completed:

Tordoff, M.G. Obesity by choice: The powerful effect of nutrient availability on nutrient intake. American Journal of Physiology, 282: R1536-R1539, 2002.

The consumption of nutrients by rodents is markedly influenced by the number of containers of each nutrient provided. Most rats given a choice from separate sources of protein, carbohydrate, and fat thrived if given one cup of each but half failed to thrive if given one cup of each and three extra cups of carbohydrate or fat. Rats given five bottles of sucrose solution and one bottle of water became fatter than rats given five bottles of water and one of sucrose. These studies in rats may point to a model for human obesity, in which the availability of food can override physiological controls of ingestion.

Tordoff, M.G. and Bachmanov, A.A. Influence of the Number Of Alcohol and Water Bottles on Murine Alcohol Intake. Alcoholism: Clinical and Experimental Research, 27, 600-606, 2003.

Background: Most work to understand the controls of alcohol intake by animals involves the “two-bottle choice” method in which a choice is given between a bottle of alcohol and a bottle of water. Recent experiments involving other nutrients suggest that intakes are profoundly influenced by the number of nutrient choices available. Here, we extended these observations by measuring the alcohol consumption of mice and rats given multiple choices of water and alcohol.

Methods: Four experiments were conducted. In Experiment 1 and 2, male C57BL6/J (B6) mice, 129X1/SvJ mice, or Sprague Dawley rats received a series of six 72- or 48-h tests in which the number of bottles of 10% alcohol and water was manipulated. One test involved the typical two-bottle choice. In the other five, the rodents always had six bottles with 1, 2, 3, 4, or 5 containing 10% alcohol and the rest containing water. In Experiment 3, separate groups of B6 mice received for 16 consecutive days (a) the typical two-bottle test, (b) 5 alcohol bottles and 1 water bottle, (c) 3 alcohol bottles and 3 water bottles, or (d) 1 alcohol bottle and 5 water bottles. In Experiment 4, groups of B6 mice received either a typical two-bottle test or 5 alcohol bottles and 1 water bottle for 24 days. Plasma alcohol concentrations were measured in these mice on Days 2, 8, 16 and 24.

Results: In all experiments, the volume of alcohol consumed was strongly and positively related to the number of alcohol bottles available and inversely related to the number of water bottles available. The effect of alcohol availability on alcohol intake persisted for at least 24 days.

Conclusions: Alcohol intake is strongly influenced by availability. The results point to a simple method of manipulating murine alcohol intake over a wide range. They provide an animal model that might be useful for understanding the influence of alcohol availability on human alcohol consumption.