Lithium induces dose-related increases and decreases in activity levels in the rat.

The effect of intraperitoneal lithium chloride on the activity levels of rats was measured by counting photocell interruptions in an open field. Treatment with 0.15 mEq/kg increased activity and 1.5 mEq/kg decreased activity. In a second experiment behavioral observations were added to the photocell counts of open field activity, and the increase observed with 0.15 mEq/kg LiCl in Experiment 1 was compared with the increase in open field activity produced by 0.4 g/kg ethanol. The two drugs produced similar increases in cell counts and walking, and similar decreases in sitting and sniffing. Lithium produced significantly more rearing and behavior directed at the cage than did ethanol. Following Johnson's hypothesis of lithium action, these findings are discussed within the context of lithium-induced changes in responsiveness to the environment. We suggest that, at 0.15 mEq/kg, lithium chloride might increase reactivity to the environment.