Lithium(Li) salt is. a kind of effective drug commonly used in the treatment and prevention of mental disorders

but its active mechanism is still not well understood. Getting on for twenty years

many research have been reported on relationship between Li salt and second messenger system

especially the effect of Li salt on adenylate cyclase. Identical result is not obtained and there are few reports on brain calmodulin (CaM) activity change by Li salt. The aim of present expcri- ment is to determine the content of CaM in raet brain by phosphodiesterase (PED) method after chronic application of Li salt and discuss preliminary the molecular mechanism of Li salt action. The result showed that marked change has happened in the content of CaM in rat brain after chronic application of Li salt. It is ins-plied that Li salt brings its action into play probably by changing the content of CaM in rat brain