with alcohol vapor for a period of days (Goldstein, Pal 1971). Recently, interest has increased in exposing animals to chronic, intermittent periods of vapor, which increases the intensity of withdrawal (Becker, Lopez 2004). Dependence cannot be measured directly, but must be inferred from the appearance of signs of withdrawal when drug administration ceases (Kalant et al. 1971). In mice, the most frequent index of withdrawal is the appearance of a handling induced convulsion that waxes and wanes in severity (Goldstein, Pal 1971). In rats, other physical and behavioral signs are used. Both species share with humans a wide spectrum of withdrawal symptoms (Friedman 1980).
