At least two different isoforms of Na,K-pump are expressed in the artery wall: a1 is the housekeeping isoform, homogeneously distributed through the membrane of vascular smooth muscle cells (VSMCs) whilst the a2 isoform has less well defined function and is spatially restricted. We have previously demonstrated that intercellular communication in the vascular wall is regulated through a spatially restricted interaction between a Na,K-pump with high ouabain sensitivity and the Na/Ca-exchanger (Matchkov et al., 2007). This interaction modulates synchronized VSMCs oscillatory activity, i.e. vasomotion. We have hypothesized that the a2 isoform has this function. We transfected cultured SMCs (A7r5) and rat mesenteric small arteries in vivo with siRNA against the a2 isoform. Non-related siRNA transfection served as a control. The functional results were tested in vitro 3 days later. Electrically coupled A7r5 cells were uncoupled when the Na,K-pump was inhibited by 10 mM ouabain and no additional effect of a putative gap junction blocker, b-glycyrrhetinic acid was seen. Downregulation of the a2 isoform reduced coupling and made A7r5 insensitive to ouabain. The arteries downregulated for the a2 isoform had significantly reduced amplitude of noradrenaline (NA)-induced vasomotion. Surprisingly, the arteries downregulated for the a2 isoform had reduced sensitivity to NA. Although ouabain increased the NA sensitivity in the control arteries, it had no effect on a2 downregulated arteries. Our results confirm the importance of the a2 isofom of the Na,K-pump for intercellular coupling in the vascular wall. Our findings also demonstrate that knock-down of the a2 isoform has a different effect on NA sensitivity compared to inhibition of the a2 isoform. This may be due to activation of a signaling cascade when ouabain binds to the pump or to an effect on protein expression of the a2 isofom downregulation.