Detailed protocols have been published in Crabbe et al.,
Two tasks were used to test motor incoordination as a behavioral index of ethanol intoxication.
2. Grid test
EtOH dosingThe short measurement names use the following ethanol dosage codes:
Balance BeamBeams of equal height (54.5 cm) and length (104.1 cm) but variable widths (12.7, 15.8, or 19.0 mm) were used. The goal was to test each mouse at a single dose of ethanol (0, 1.0, 1.2, 1.4 g/kg) on all three balance beams.
Mouse cages were randomized for testing order. Mice were trained on the 12.7 mm balance beam the day before data collection. On test day following 1 hr of habituation in the test room, mice were injected (i.p.) at 3-min intervals with saline (Baxter Healthcare, Deerfield IL USA) or one of three doses of ethanol (Pharmco Products, Brookfield CT USA; 1.0, 1.2, or 1.4 g/kg; prepared as 20% vol/vol in saline). Mice were injected by one technician. After 10 min in a holding cage, a second technician tested the mice across three balance beams of increasing widths (12.7, 15.8, 19.0 mm). Hindlimb dragging, falling, and hanging were noted and the number of missteps recorded. 'Corrected' missteps were calculated by subtracting the strain mean misstep count for the saline group from the individual's ethanol-treatment misstep score.
Mice were returned to the animal facility and housed with their original cage mates in the same home cage.
The number of missteps crossing each balance beam at 0
(baseline), 1.0*, 1.2*, and 1.4* g/kg ethanol are available
for analysis. (*normalized to baseline). Additional data
are available in the supplemental data set
including scores for hanging or falling from the balance
beam and raw misstep data.
Grid TestOne week following the balance beam test, the ataxic effects of ethanol were measured in the grid test apparatus. The goal was to acquire baseline data over three consecutive days of grid habituation testing and then on the fourth day to test each mouse at one of three doses of ethanol.
The apparatus is a 15 x 15 x 20 cm clear acrylic box placed in the center of a DigiScan activity monitor (AccuScan, Columbus OH USA) with a 1.25 cm2 wire grid 1 cm above a metal plate floor. An electrical circuit is completed and recorded by custom software when the mouse's foot slips from the grid onto the metal plate. Locomotor activity is recorded by photo-beam interruptions.
Mice were allowed to acclimate to the procedure room for 1 hr on each test day. On days 1, 2, 3 the mice were placed into the grid apparatus immediately following saline injection (i.p.) and tested. On day 4, mice were injected with one of three doses of ethanol (1.5, 2.0, 2.5 g/kg) before placement in the test apparatus. Mice were returned to their home cage and colony after each day of testing.
Distance traveled and the number of missteps (foot slips)
are available for analysis (grid habituation data from day 3
and grid testing data from day 4). Additional data are
available in the supplemental data set
including grid habituation data for days 1 and 2, and grid testing
data from 5-min intervals.