Ethanol's effects on gait dynamics in mice investigated by ventral plane videography

Background: Performance of mice in motor function tests for ethanol sensitivity is often task dependent, not reflective of coordinated movement, and reported qualitatively. Therefore, we applied a new imaging technique to record and quantify coordinated gait dynamics in mice in response to ethanol. Methods: We applied ventral plane videography to record and report gait indices in mice walking on a transparent treadmill belt. We examined the effects of ethanol on gait in C57BL/6J (B6) and DBA/2J (D2) mice walking at a speed of 25 cm/sec. B6 and D2 are two inbred strains that are widely used to study the genetic influences of ethanol on motor function. Results: Gait posture in D2 mice was less stable than in B6 mice. B6 mice always showed an alternate step sequence, whereas D2 mice sometimes showed cruciate and rotary step sequences. Ethanol in increasing doses increased stride frequency, decreased stride length, and increased stride length variability in D2 mice but not in B6 mice. The forelimb braking duration was significantly shortened and the hind limb propulsion duration was significantly prolonged with a high dose of ethanol in D2 mice but not in B6 mice. Differences in gait indices between the two strains of mice were more pronounced of the forelimbs with the highest dose of ethanol (2.75 g/kg). Conclusion: Our data suggest that the higher susceptibility of D2 compared with B6 mice to the effects of ethanol on motor function may be attributed to less stable basal gait characteristics that are perturbed by ethanol. The ability of this method to quantify step sequence patterns and gait indices of forelimb and hind limbs could provide new data regarding ethanol-induced motor incoordination.