Detailed methods for taste phenotyping mice using the two-tube choice test

 

To construct drinking tubes read this.

 

Filling the tubes

 

“Water” tubes are filled via submersion in deionized water.  The stoppers are then securely twisted into the tube. 

“Taste solution” tubes are filled with a wash bottle.  We leave approximately one inch of air space in the drinking tube to prevent a vacuum.  Tubes are transported in an inverted position (resting on the rubber stopper) to prevent fluid leakage and contamination.

 

Putting the tubes on the cages

 

Before reading the tubes, they are righted and gently shaken to dislodge air bubbles.  Each tube is held vertically and the position of the meniscus is read.  The scale on the tube is in 0.2 ml increments but we interpolate to the nearest 0.1 ml.  If the meniscus falls between two tenths, we read to the greater number.  Finally, tubes are inserted into the modified cage lids, with minimal jarring.

 

There should be a picture of a mouse cage with two drinking tubes here

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.  A mouse cage with two drinking tubes held in place by a steel spring

 

Taking the 24 hr measurement

 

Typically, after 24 hr mouse intakes are recorded.  Each tube is held vertically and the position of the meniscus is read.  The tubes are then replaced with their positions switched.   Here is an example of the datasheet we use and what it looks like when it is filled in.

 

Removing the tubes from the cages at 48 hr

 

At 48 hr, mouse intakes are recorded again using the same methods as at 24 hr, except (of course) the tubes are not replaced on the cage.

 

Reusing the tubes

 

After each experiment, the tubes (including the spouts) and stoppers are soaked for a minimum of 15 minutes in Liqui-Nox detergent (Fisher Scientific) and hot tap water.  The tubes are scrubbed with a transfer pipette brush that also reaches into the sipper tube.  Tubes are rinsed three times in hot tap water, twice in deionized water, then drained and air dried in an inverted position.  Stoppers are soaked then washed en masse by vigorous shaking, then they are rinsed the same as the tubes.

 

Figure 2.  Drinking tubes and their stoppers drying  in preparation for their next use.

 

Figure 3.  One of many racks holding mice undergoing two-bottle choice tests.