No abstract

Mice from 15 standard inbred strains were tested for sensitivity to several effects of acute diazepam (DZ). Strains differed in sensitivity to DZ-induced: low-dose stimulation and high-dose depression of locomotor activity, hypothermia, and ataxia assessed on a rotarod. Correlations among strain means indicated that sensitivity to a particular effect of DZ generalized well across doses. Sensitivities to some of the different behavioral responses also were significantly correlated. For example, strains sensitive to DZ-induced increases in activity were significantly less sensitive to the drug's hypothermic effects. These results suggest that there are multiple genetic determinants of behavioral sensitivity to DZ effects. That is, genetically influenced sensitivity to DZ is not monolithic but is somewhat specific to the particular response variable studied, a result that also characterizes genetic control of responses to other drugs.

We have developed a precise quantal method for assessing the sensitivity to ethanol in the mouse. Mice placed on a clamped stationary horizontal dowel are scored ataxic or not ataxic depending on whether they are able to remain on the dowel during a 30-s observation period. A threshold blood ethanol concentration is determined by assaying tail blood drawn immediately upon recovery from ethanol-induced ataxia. This threshold is quite reproducible within a population of Swiss-Webster mice (coefficient of variation 9%). The precision of this method allowed us to follow the onset of rapid tolerance during a series of sequential IP ethanol doses. Tolerance persisted overnight in the absence of ethanol, and was found not to increase further with additional ethanol exposure on 2 subsequent days. The observed tolerance was shown not to be due to circadian changes in ethanol sensitivity or repeated practice on the task, indicating a true tissue tolerance.

Overall, these results suggest that there are multiple genetic determinants of behavioral sensitivity to PB effects. That is, genetically influenced sensitivity to PB is not monolithic, but is somewhat specific to the particular response variable studied, a result that also characterizes genetic control of responses to other drugs.

We have recently described a telemetry/microcomputer system to monitor core temperatures in rats. We implant a miniature transmitter (Mini-mitter) into the peritoneal cavity of the rat, allowing us to obtain temperatures around the clock without handling the animals or disturbing the light-dark cycle. In the present study we describe the temperature effects of ethanol doses ranging from 2 to 6 g/kg. Baseline temperatures were collected for 2 days before drug was administered. Subsequent computer analysis then allowed us to compare experimental results in each animal with its own baseline temperature to allow for individual and circadian temperature differences. In preliminary studies we observed the well-known dose-dependent hypothermic effect of ethanol. However, by observing animals continually over 4 days we also observed a period of rebound hyperthermia beginning at about the time of complete ethanol elimination and persisting for several days. During this period daytime temperatures remained at the normally high night-time level. This may be evidence of a mild abstinence syndrome, or alternatively, may be due to a disruption of the normal circadian temperature rhythm.