The effects of diisopropyl phosphorofluoridate (DFP) on time perception in rats

The hypothesis that DFP alters circadian rhythms by altering the output of an "internal clock" which is also used to time events in behavioral tasks was tested. Since any clock has a mean rate (ticks/unit time) and an associated variance (changes in the rate across time), measures of time perception which depend upon both the mean clock rate and its variance (discriminability, A'), or only the mean clock rate (Bisection Point) were examined. In Experiment 1, two groups of rats were trained to discriminate between a standard duration and six comparison durations of a light. Six weeks following three injections of DFP (1.0 mg/kg/week) or vehicle (saline and 5% alcohol), the discriminability (A') between the standard and comparison durations was reliably reduced for the DFP-treated animals. In Experiment 2, rats were trained to perform on a temporal bisection task. Relative to performance during the weeks following vehicle (peanut oil) treatments, discriminability (A') during the weeks following treatment with DFP (1.0 mg/kg/week) was reliably degraded but measures of the Bisection Point were unaffected. Since Experiments 1 and 2 both used a light duration as a discriminative stimulus, Experiment 3 examined the possibility that DFP treatments produced a change in visual function rather than clock function. Two groups of rats were trained to discriminate between light-on and light-off periods in a standard free-operant successive discrimination paradigm. No changes in discriminability or response rates were evident following two injections of DFP (1.0 mg/kg/week) or vehicle (peanut oil).(ABSTRACT TRUNCATED AT 250 WORDS)