Lead-produced changes in the relative rate of open field activity of laboratory rats

Four groups of rats, continuously exposed to one of two lead acetate solutions, ad lib water or a limited amount of water, were tested for three daily 5 min periods on the open field. The effects of treatment on activity, relative to animals drinking ad lib water, depended upon the concentration of the lead acetate solution. Animals exposed to a 10^?4 M lead acetate solution showed increased overall activity while animals exposed to a 10^?2 M lead acetate solution showed changes in the relative rate of activity. Activity was not affected by limiting the amount of water consumed. These findings illustrate the importance of recording activity in a manner which allows assessment of changes in activity as well as absolute level.