Ionotropic purinoreceptors (P2XRs) in renal vascular smooth muscle cells (RVSMCs) are involved in mediating the sympathetic control and paracrine regulation of renal blood flow. Activation of P2XRs elevates [Ca2+]i in RVSMCs triggering their contraction, leading to renal vasoconstriction and decrease of renal blood flow [1]. In the present study we characterised the expression of P2XRs and P2XR-mediated transmembrane ionic current (IP2X) in RVSMCs isolated from interlobar and arcuate rat kidney arteries [2]. The expression of P2XRs in isolated RVSMCs was analysed by RT-PCR. IP2X and membrane potential were recorded using amphotericin B perforated patch-clamp method. Data are presented as mean ± S.E.M. RT-PCR analysis on 5×(~500 per sample) single RVSMCs showed the presence of genes encoding P2X1 and P2X4 receptors. Under current-clamp conditions both 10 µmol/L ATP and 10 µmol/L of the selective P2XRs agonist αβ-meATP evoked a spike-like membrane depolarization followed by a sustained depolarization, thus, linking P2XRs in RVSMCs to sympathetic control of renal vascular tone. Under voltage-clamp conditions 10 µmol/L of αβ-meATP evoked IP2X with an average peak current density of 111±5 pA/pF (n=123) to that of 82±8 pA/pF (n=7) evoked by 10 µmol/L ATP. 10 µmol/L UTP evoked significantly smaller currents with an average peak current density of 3±2 pA/pF. IP2X showed virtually complete recovery within 7 min (n=6-7). The voltage dependence of the IP2X showed inward rectification and a reversal potential around +5 mV (n=5). Within the range of concentrations between 10 nmol/L and 100 µmol/L αβ-meATP activated IP2X concentration dependently with EC50=1.1±0.1 µmol/L (n=5-6 for different concentrations of αβ-meATP). Incubation of RVSMCs with selective antagonist of P2X1 receptors NF279 inhibited IP2X in dose-dependent manner and suggested the contribution of two types of functional P2X1 receptors. IP2X component with higher sensitivity to NF279 was characterised by an IC50=6.8±0.4 nmol/L (n=5-12) whilst the component with lower sensitivity to NF279 was characterised by an IC50=71.4±2.8 µmol/L (n=5-12). The high sensitivity of the first component to NF279 was consistent with the high affinity of the cloned P2X1 receptor to this drug [3]. The sensitivity of the second component was close to that reported for heteromeric P2X1/4 receptor [4]. Our results directly demonstrated the expression of two types of functional P2XRs in RVSMCs (1) monomeric P2X1 and (2) heteromeric P2X1/4 receptors. Thus, our study identified important targets for possible pharmacological intervention in the sympathetic control of renal circulation.