Specific activity of Carboxyl esterase (CE) was estimated for young,old (2-4 and 16-18 months) and for similar groups of Lithiumtreated male Albino Sprague dawley rats whole brain cells. Rats ofboth age groups were orally administered with 37mg of Lithiumchloride (LiCl2) per kg body weight daily for 10 days. Old rat brainsLiCl2 treated showed significant increased CE specific activity of0.076 IU/mg protein in crude, 0.1445 IU/mg protein in Ammoniumsulphate precipitated and 0.5827 IU/mg protein in ion exchangefraction than their control. So the highly purified samples ofcarboxyl esterases obtained with LiCl2 treated brain. Enzymekinetics of substrate concentration showed Km of 0.2 mM andVmax of 52.631, indicating higher CE activity at pH-6 and at 60oCtemperature in crude extracts of control old rats. The crude brainsamples of both aged groups LiCl2 treated showed an intense bandpatterns in Native PAGE for CE expression than their controls.Thus, LiCl2 elevates carboxyl esterase in each step of purificationand in future it activates drug metabolism to treat various brainrelated disorders.