Effects of lead on the behavioral complex stereotypes and regional brain dopamine levels in rats

The behavioral complex stereotype responses such as rearing, preening, scratching and biting were observed in an open-field situation in rats ingesting 2% lead acetate in drinking water for a period of 30 days. Endogeneous levels of dopamine were measured spectrophoto-fluorometrically in three brain regions; namely, cerebral cortex, cerebellum, and brain stem. The behavioral rearing response was diminished on day 3 and between days 7 to 22 of lead ingestion as compared to the control. Subsequently, this response was progressively increased from day 26 to 30. The animals showed depressed response of preening on day 2 and 6. From day 9, the preening response exhibited a continuous increasing pattern until the last day of the experiment. However, the complex stereotypy of scratching behavior of rats showed a parabolic pattern against the normal scratching behavior. A similar pattern of biting response has been observed in lead-intoxicated animals. Both the scratching and biting responses were higher than the control at the end of the experiment. Dopamine levels increased in the cerebral cortex on days 13, 23, and 30. In the cerebellum, the dopamine level was reduced on day 13 and increased on day 23. The brain stem exhibited increased level of dopamine on days 3, 13, 23, and 30 as compared to the control. These evidences clearly show an association of dopamine with complex stereotypy behaviors of lead intoxication.