ACTIVITY RHYTHMS IN MICE .3. STABILITY AND PLASTICITY OF RHYTHM CHARACTERISTICS IN EXPERIMENTAL AND ENVIRONMENTAL-CONDITIONS

The expression of a biological rhythm as measured by a given descriptor results from a set of components: the subject, the measuring device, and the experimental conditions. Rhythm of activity under four experimental conditions was observed in two strains of mice: BALB/c and C57BL/6. Condition 1, the optimal normal situation, was used as a reference; condition 2 was a retest of the animals used in condition 1 twelve days later condition 3 tested animals for a period of 3 days in a food-deprivation situation; in condition 4, animals were isolated for 2 weeks prior to testing. Data analysis of rhythm of activity in the synchronic mode is based on a series of tests in the frequency and temporal domains. Analysis of condition-linked variation in the findings indicates that these parameters are only slightly affected by the four experimental conditions. The results, however, can be hierarchized according to condition and according to the kind of parameter. The temporal parameters are more sensitive than the frequency parameters, the least sensitive being the temporo-frequential measures. Isolation produces the greatest variation in parameter magnitude. The results show that rhythm of activity is fairly stable across a number of experimental conditions, a finding that could considerably simplify experimental protocols.