[Lithium as a psychotropic drug. Experimental studies on its mechanism of action]

The effect of lithium on the cAMP metabolism was studied in rat brain. It was shown that: 1. Acute and subacute doses of lithium have no effect on the cAMP content of the forebrain of rats while chronic administrations significantly reduce the cAMP level in the brain by 30%; 2. the activities of the cerebral cAMP and cGMP phosphodiesterases are not affected by lithium in vitro; 3. the adenyl cyclase in rat brain homogenates stimulated by sodium fluoride and noradrenaline is inhibited dose-dependently in the mM range and 4. adenyl cyclase in isolated cells from the rat forebrain is very sensitive to inhibition by lithium in the therapeutically relevant microM range. With all due caution in transferring experimental results to the mechanisms of action of drugs in humans, it is obvious from these results in comparison with the effect of lithium on hormone-sensitive adenyl cyclases from extracerebral tissues that the effect of lithium salts in manic psychoses may be due to inhibition, and their prophylactic action probably to a "stabilizing" of cerebral adenyl cyclases.