Circadian rhythm of stereotyped complex behaviours in rats in environmental lead exposure

1. Stereotyped complex behaviours are present in a number of psychotic illnesses, neurological diseases and even can be generated in response to chemical environment (e.g., drugs or toxins). 2. The circadian rhythm of complex behaviours such as, rearing, preening, scratching and biting/licking was evaluated in an open-field situation in rats exposed to lead (2% lead acetate in drinking water for 30 days). 3. The circadian rhythm of rearing patterns showed depressions from 2 to 14 hr on day 3 and 13, and from 2-6 hr on day 23 (it elevated at 10 hr), whereas increased pattern was apparent at all test periods (except at 6 hr) on day 30. 4. Increased responses of circadian rhythm of preening behaviour were obtained at 18 hr (with decrease at 22 hr) on day 3, at 6 and 14-22 hr on day 13 and, at all the test periods on day 23 (except at 6 hr) and on day 30. 5. The rhythmic patterns of the scratching behaviour showed elevations at each test period as observed on day 3, 13, 23 and 30. The responses in lead-intoxicated rates, however, showed depressions in the light-period and augmentations in the dark-period. 6. The biting/licking behaviours indicated increased patterns of the circadian rhythm attaining a parabolic response, which were inconsistent to the scratching behaviour patterns. Amongst lead-intoxicated rats this behaviour exhibited depressed responses in light-period, whereas in dark-period it showed elevations.