Hormetic Neurobehavioral effects of low dose toxic chemical mixtures in real-life risk simulation (RLRS) in rats

The current study aims to assess the long-term effects of very low dose exposures to a complex chemical mixture on motor performance and behavioural changes in rats. For twelve months (equivalent to thirty years in human terms), four groups of Sprague Dawley rats (five males and five females per group) were exposed to a thirteen chemical mixture (in drinking water) in doses of 0, 0.25, 1 and 5xADI/TDI (acceptable daily intake/tolerable daily intake) (mg/kg body weight/day). After twelve month exposure, the rats' motor performances were assessed by rotarod test, and their behavioural changes were assessed by open field exploratory test and elevated plus maze test. Exposure to the chemical mixture resulted in a statistically significant increase in the locomotor activity quantified by the number of crossings over external squares and in the spatial orientation activity quantified as the number of rearings in the lower dose group (0.25xADI/TDI) compared with the control group (p < 0.05). No significant changes were observed in the two higher dose groups (1xADI/TDI, 5xADI/TDI) compared with the control group. The administration of a very low doses of a cocktail of 13 chemicals led to a dose-dependent stimulation of the nervous system, rather than its inhibition.