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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. [ABSTRACT FROM AUTHOR]

Background: Acute functional tolerance (AFT) to ethanol-induced hypnosis is one of the main factors that affect the duration of ethanol-induced loss of righting reflex (LRR: "sleep time"). Investigators who use duration of LRR as a measure of ethanol-induced sedation should consider the potential magnitude and time course of this neuroadaptation when interpreting their results. However, AFT to the hypnotic effects of ethanol has not been well characterized. The present study explored this form of AFT using a novel method of monitoring LRR in mice. Methods: Genetically heterogeneous mice were used to study effects of dose and time on the development of AFT. Mice were treated with different dose regimens and tested for LRR after hypnotic doses using a cylindrical restrainer. Measures of initial sensitivity and AFT to ethanol-induced hypnosis were calculated and analyzed. Inbred strains of mice were then characterized for AFT magnitude after a single ethanol dose. Results: Results showed that (a) AFT developed in a dose-dependent fashion but attained an apparent maximum value; (b) AFT to ethanol-induced hypnosis could develop partially after a small, subhypnotic dose; (c) AFT developed very rapidly and approached its maximum for a given dose by the 10th min after injection of ethanol; and (d) AFT has a strong genetic component. Conclusion: Although specific for AFT to the hypnotic effects of ethanol, the present findings expand general knowledge about acute tolerance and should also be useful for investigators who use loss of righting reflex as a measure of ethanol sensitivity. [ABSTRACT FROM AUTHOR]

Locomotor activity responses to sub-hypnotic doses of ethanol (ETOH) were assessed in selected lines of mice (LS and SS), inbred strains, and their F1 hybrids. Data were obtained as photocell beam interruptions in a 15-min test for a dose range of 0 to 2.75 or 3.5 g/kg for LS and SS mice, respectively. Biphasic dose-response curves were obtained for LS and SS mice with the SS mice showing a sedative limb of the dose-response curve shifted to the right. The effects of 2.0 g/kg ETOH were also assessed in a diallel cross of the selected LS/SS lines and C57BL/6Abg and MOLD/RkAbg inbred strains. The 2.0 g/kg dose produced a wide range of responses, from sedation in C57BL/6Abg mice to extreme activation in SS and MOLD/RkAbg mice, and no effect in LS mice. The responses of F1 hybrids reflected a typical pattern of partial dominance, with heterosis in some crosses. When present, dominance was in the direction of greater locomotor activation. These patterns were confirmed by biometrical genetic analysis of the 4 × 4 diallel cross of the two lines and the two inbred strains. The data indicate that loci in addition to those responsible for selection for sedative sensitivity in LS and SS mice can influence locomotor activation produced by sub-hypnotic ETOH doses, and that SS and MOLD mice show locomotor activation for different genetic reasons. [ABSTRACT FROM AUTHOR]