A Sliwa

The usage of video analysis system for detection of immobility in the tail suspension test in mice.

The Tail Suspension Test (TST) is a commonly used screening method for antidepressants properties of drugs in mice. To date, immobility in the TST was scored live, by an observer, or automatically, using devices in which mouse movements were detected by a strain gauge. In this study we tested whether the EthoVision video analysis system can be used reliably and accurately for automatic recording and scoring of duration of immobility in the TST. First, the duration of immobility in two mouse lines was assessed. Different mobility thresholds of the video analysis system were applied and the results compared with the duration of immobility scored manually. Next, the selected immobility threshold was applied to determine the dose-response curves for the drug venlafaxine. Finally, scores from the video analysis system were compared with scores generated by an electromechanical strain gauge device (Med Associates) and a human rater. It was found that the EthoVision system could reliably and accurately quantify the duration of immobility in the TST. The best setup was an immobility threshold ranging from 2 to 3 percentage change in the object area. The EthoVision system was effective in detecting the differences between the mouse lines and the dose response to venlafaxine. The results obtained using the video analysis system were similar to the scores yielded by a human rater and the strain gauge device.

Differences in ethanol drinking between mice selected for high and low swim stress-induced analgesia

Alcoholism is a complex disorder, still not fully understood, in which environmental and inherited risk factors play essential roles. Of particular importance may be chronic exposure to stress thought to increase preference for ethanol in genetically susceptible individuals. Animal and human data suggest that the opioid system may be involved in the development of alcohol dependence. We studied the effects of chronic mild stress (CMS) on the voluntary intake of 8% ethanol in the mouse lines displaying high (HA) or low (LA) swim stress-induced analgesia. These lines differ in the activity of the endogenous opioid system. Normally, 8% ethanol is aversive to rodents. We found that LA mice with the low opioid system activity exposed to CMS manifested greater ethanol intake than under no stress conditions. No such effect of CMS on ethanol consumption was observed in HA mice that display the enhanced opioid system activity. We conclude that CMS imposed on individuals with a genetically determined low opioid activity may favor the development of ethanol abuse.

Lipopolysaccharide does not affect acoustic startle reflex in mice.

Bacterial endotoxin (lipopolysaccharide; LPS) evokes in rodents an adaptive sickness behavior. It also produces changes in stress hormones secretion and activity of brain serotonergic and noradrenergic systems that have been implicated in stress responses, fear, and anxiety. Acoustic startle reflex (ASR) is regarded as a protective behavioral response that is enhanced in threatening situations or following an aversive event, and it can be modulated by physiological and emotional state of an animal. Effects of intraperitoneal injections of LPS on ASR, prepulse inhibition (PPI), locomotor activity in open field, and blood plasma corticosterone concentration were studied in lines of mice that display high (HA line) or low (LA line) swim stress-induced analgesia and also differ in emotional behaviors, including the magnitude of ASR. In both lines LPS produced robust sickness behavior, as evidenced by a decrease in locomotion and body weight, and an increase in corticosterone concentration. However, in neither line LPS injections affected responses to acoustic stimuli as assessed by the ASR and PPI magnitudes. The findings suggest that in sickness behavior induced by LPS the protective responses to salient environmental stimuli are not impaired. The significance of this finding for the concept of sickness behavior is discussed.