Central and peripheral effects of lithium on amphetamine-induced hyperactivity in rats.

Rats received 0.15 M LiCl either as a central treatment in the lateral cerebroventricles (2x20 microliter/rat) or as a peripheral treatment in the peritoneal cavity 15 ml/kg). The central treatment produced high lithium concentrations (1-1.2 mmol/kg) in the brain while peripheral treatment produced high lithium levels (1-2 mmol/1) in the blood at convenient times for behavioral tests. The central treatment antagonized amphetamine-induced hyperactivity but failed to affect open field behavior in otherwise untreated rats. In contrast, the peripheral treatment suppressed open field activity in otherwise untreated rats but failed to influence behavioral effects of amphetamine. The findings demonstrate differences between central and peripheral actions of LiCl on behavior in rats and show lithium to have central actions on hyperactivity induced by amphetamine.