Tordoff1 project protocol

Diet preference: Survey of salt preference in drinking water for males of 28 inbred strains of mice   (2001)

Tordoff MG, Bachmanov AA

See also: Tordoff1 animal documentation


Equipment: Construction of drinking tubes and other experimental procedures are given in detail at www.monell.org/MMTPP. Each drinking tube consisted of a 25 milliliter plastic serological pipette with 0.2 milliliter gradations (Fisher cat no. 13-678-14B). This was connected to a 63.5-millimeter long stainless steel straight sipper tube (Unifab, Cat. No. US-171-25) with a 15-millimeter piece of silicon tubing (Cole Palmer, Cat. No. 06411-76). The top of the pipette was closed with a size 00 rubber stopper. Tubes were always given in pairs, with one containing deionized water and the other containing the taste solution. The drinking tubes were placed to the (experimenter's) left of the food hopper. The spouts extended ~25 millimeters into the mouse cage and their tips were ~15 millimeters apart. Each spout had a tip with a 3.175-millimeter diameter hole from which the mice could lick fluids.

Test Procedure: The experiment was conducted in two testing sessions with different sets of inbred strains (see submitted data set for session information). During the first 4 days of each testing session, baseline food and water intakes were measured, with two tubes of water as the only source of fluid. Then, mice received a series of two-bottle choice tests, one with deionized water and the other with NaCl, KCl, CaCl2, or NH4Cl (ascending concentrations of specific mineral solutions were given over time). The concentrations used were chosen based on previous work and pilot projects so as to span the range from indifference to strong avoidance by most strains of mice. Each test was 48 h in duration. The positions of the tubes containing taste solution and water were switched after 24 h to control for side preferences. Intakes were measured to the nearest 0.1 milliliter at the end of each test. Extensive experience has shown that fluid spillage and evaporation is <0.2 milliliter over 48 h with these procedures, and so these were ignored.

Body weight was measured (to the nearest 0.1 g) at the beginning of the food intake test, and at the beginning and end of each solution intake test.

Total fluid intake was calculated as the sum of the taste solution intake and water intake.

Where indicated fluid intakes were adjusted (adj) for body weight by dividing each intake by the mouse's average body weight and multiplying this by 30 (the approximate weight of an adult mouse).

Percent preference = (solution intake/total fluid intake) x 100

 

Notes: The missing data code OT (other) was entered for data lost due to spilled or blocked tubes or other technical problems. When intake from one tube was compromised, intake from the other tube was discounted from analyses.