Objective  To investigate the expression of inositol 1,4,5?triphosphate receptors (IP  3R) in cultured vascular smooth muscle cells(VSMC) of rat.Methods  Expression of IP  3R mRNA in VSMC was measured by reverse transcription  polymerase chain reaction (RT  PCR).The amplified PCR products were subcloned and sequenced.The immunocytochemical analytic technique was used to observe IP  3R expression intracellularly.Results  Three subtypes of IP3R expressed within rat VSMC were identified and the short non  neuronal form of type I IP  3R was detected.Immunofluorescence staining indicated that the IP  3R was preferentially located at the peri  nuclear membrane in cellular plasma.Conclusion  The present study confirms that three subgroup of IP  3R are expressed in VSMC,and it suggests that IP  3 signal transduction pathway within a single cell be of heterogeneity.