Abstract: Free intracellular Ca²⁺(Ca²⁺i) levels in rat brain were measured by Ca²⁺——sensitive fluorescent indicator Fura-2/Am and the effects of sennoside(SEN),polysaccharides from Rheum palmatum(RPP)and emodin(EMD)were studied.ResuIts showed that the restingCa²⁺ilevel in the brain cells was 176. 25 ± 44.67 nmol·L^-1(n=10)in Ca²⁺-free Hank’s solutioncontaining EGTA 0,5 mmol·L^-1.After adding CaCl₂(2 mmol·L^-1)and KCI(120 mmol·L^-1)to the brain cells suspension sequentially,the freeCa²⁺i levels were obviously elevated(P<0.01)compared with that of resting level.The brain cells were pretreated with SEN( 0.07,0.37mmol.L^-1) for 10 min。 In the resting or using the above doses of CaCl2 and KCI,theCa2+i wereobviously decreased compared with the control groups(P<0.01)at the same conditions.RPP dose-dependently decreased the Ca²⁺i.On the contrary,when brain cells were pretreated with EMD(0.037 mmol·L^-1) for 10 min, theCa²⁺i were obviously increased compared with the controlgroups(P<0.01)at the same conditions.The results showed that EMD could not only promote therelease of intracellular Ca²⁺ but also the influx of extracellular Ca²⁺, The opposite effects of thedifferent active components of rhubarb on theCa²⁺i levels suggest that rhuharb may have differentkinds of regulatory functions on brain cells.