Assessment of behavioral effects of tetrachloroethylene using a set of time-series analyses.

A systematic approach to the analysis of time-series data for spontaneous locomotor activity in the rat was developed to evaluate the behavioral effects of chemical substances. Chronogram, spectral analysis, analysis of the slope of fluctuation, and the cosinor method were used to analyze data obtained by continuously recording spontaneous locomotor activity in the rat. Under synchronized conditions, a circadian period of 24 h was observed and the 1/f fluctuation, in which the power spectral density is inversely proportional to frequency, was confirmed. The 1/f fluctuation was considered to reflect the fractal-like structure of ultradian components of spontaneous locomotor activity. IP administration of 1.0 g/kg body weight of tetrachloroethylene at 0900 h produced a remarkable phase-shift (4.0 +/- 0.9 h) in the activity rhythm and an increase in the slope of fluctuation (0.4 +/- 0.1) in contrast to a relatively smaller decrease in the total amount of spontaneous locomotor activity. These behavioral effects of tetrachloroethylene were dose-dependently lower at lower doses. The present study demonstrated the usefulness of our systematic approach in evaluating the behavioral effects of chemical substances.