In vivo distribution of lithium in plasma and brain.

A single administration of LiCl (0.5, 2 and 4 mmol/kg) to adult male albino rats produced a dose dependent increase of Li level in plasma, whole brain and brain regions. The concentration of Li in whole brain and brain regions was much less than that in plasma. Further, it is also found that concentration of Li in plasma reached a peak at 8 hr while that of Li in whole brain and brain regions reached a peak at 12 hr after the administration. The distribution and retention of Li was found to be highest in hypothalamus followed by striatum, pons-medulla, cerebellum and cerebral cortex. Daily administration of LiCl at a dose of 0.5 and 2 mmol/kg/day showed a time and dose dependent increase in plasma Li level up to a period of 21 consecutive days. But at higher dose (4 mmol/kg/day), on the other hand, under similar condition showed a time dependent increase in plasma Li level up to a period of 14 consecutive days and then gradually decreased with prolongation of treatment to 21 consecutive days. In brain there was no such decrease, rather increase in Li level was observed with the prolongation of duration of treatment, highest concentration of Li was found in hypothalamus and striatum than the rest of the brain regions. These results suggest that under short term treatment with LiCl, the clearance rate of Li in brain cell is much slower than that in plasma. Both single and long-term exposure of LiCl produces a dose dependent increase of Li in plasma, whole brain and brain regions.(ABSTRACT TRUNCATED AT 250 WORDS)