Effects of low-level lead exposure on 24 h activity patterns in the mouse

Spontaneous activity of male mice chronically exposed to lead acetate or sodium acetate was tested for periods of 24 h in their home cages and normal housing groups. Animals receiving 0.25% lead acetate showed significantly higher levels of spontaneous activity than did distilled water controls during the early part of the dark phase in two experiments, and significantly lower activity levels during the latter part. Mice receiving 0.025% lead acetate were also significantly more active than controls early in the dark phase, and either significantly higher or no different from controls latterly. Animals receiving 0.025% sodium acetate were significantly less active than controls early in the dark phase, but later were equally active. Weight loss in lead-treated animals was variable and not correlated with changes in activity levels.