Abstract: AIM: To investigate the effects of N-n-benzyl haloperidol iodide (F₂) on intracellular calcium ([ Ca²⁺ ]_i) in rat cardiomyocytes.METHODS: Cardio-myocytes were loadedwith Fluo3-AM, a calcium sensitive fluorescent dye, and the[ Ca²⁺ ]_i was determined by the use of laser scanning confocal microscope (LSCM).RESULTS:In the Tyrode' s solution with Ca²⁺ at the con-centration of 1.8 mmol·L^-1, 60 mmol·L^-1 KCl induced a rapid increase of intracellular calcium fluorescence in-tensity (FI).The FI was increased from the basic value (1.0) to 1.84±0.35 (P<0.01, n =50).With prein-cubation of cardiomyocytes with F₂ 0.1, 1, 10 μmol·L^-1, the FI elevation was inhibited in a concentra-tion-dependent manner.The calculated IC₅₀ was 1.61 μmol·L^-1.F₂ also reduced the FI elevated by 60 mmol·L^-1 KCl in a concentration dependent manner.The FI was decreased by 0.1、1、10μmol·L^-1 F₂ from 1.92± 0.42(n =50) to 1.88 ±0.39(P >0.05, n =50), 1.31 ±0.36(P<0.01, n =50), 1.09 ±0.05(P<0.01, n =50), respectively.The calculated IC₅₀ was 1.78 μmol·L^-1.F₂ had no effects of on[ Ca²⁺ ]_i in the resting state, and had no effects on intracellular calcium release induced by caffeine and inositol-1, 4, 5-trisphosphate. CONCLUSION: F₂ reduces[ Ca²⁺ ]_i.via inhibition of voltage dependent calcium channel, which is possibly in-volved in the mechanism of its protective effects on myo-cardial ischemia reperfusion injury.

Key words: haloperidol, cardiomyocytes, calcium, laser scanning confocal microscopy