Correlation of lithium effects on motor activity with its brain concentrations in rats

Effects of lithium (Li) on motor activity have been investigated at different post-drug intervals (0.5–72 hr) after adminstration of 1, 2 and 3 mequiv/kg of lithium cholride (LiCl) to rats. The activity gradually decreased until the maximum effects of these doses were observed at 8 hr, after which the activity returned to control levels (48–72 hr). Lithium concentrations were estimated in various brain areas (cortex, caudate nucleus, hypothalmus, rest of the diencephalon, midbrain, ponsmedulla and cerebellum) following administration of a 3 mequiv/kg dose of LiCl to rats at different post-drug intervals (0.5–48 hr). Lithium concentrations increased gradually reaching their peak at 8 hr in almost all brain areas except for the caudate nucleus where the peak level was achieved at 12 hr. The time-course of the depressant effect of Li on motor activity correlated with the changes in Li concentrations in the brain areas related to emotion and psychomotor activity.