Objective: The gap junction protein connexin40 (Cx40) is important in cardiovascular and renal physiology as concluded from mice globally deficient for Cx40. These mice exhibit pronounced hypertension, renin excess, and impaired conduction of vasodilator signals along the endothelium. However, the exact contribution of endothelial Cx40 vs. Cx40 expressed in renin-producing cells is unknown. Methods: We studied mice carrying a cell-specific deletion of Cx40 in endothelial (EC) or renin-producing cells (RPC) using the Cre/loxP system by means of intravital microscopy and telemetric blood pressure measurement. Results: Local stimulation of arterioles using ACh or bradykinin (Bk) elicited dilations that conducted rapidly without attenuation of the amplitude to remote upstream sites up to a distance of 1200 mm in animals carrying a floxed Cx40-gene (control). In contrast, remote dilations were significantly attenuated in EC-Cx40ko (ACh by 28%, Bk by 32%) but not in animals deficient for Cx40 in RPC. However, local and remote dilations initiated by adenosine were comparable in all 3 groups of mice in that the remote dilatory amplitude was attenuated compared to the local response. Similarly, conduction of K+-induced constrictions were indistinguishable between the 3 groups. Interestingly, EC-Cx40ko were normotensive (EC-Cx40ko: 115, control: 113 mmHg) whereas RPC-Cx40ko exhibited a significantly elevated mean arterial pressure (138 mmHg). Concomitantly, heart weight was elevated only in the latter mice. Cx37 was not retrieved in arteriolar endothelium in EC-Cx40ko, whereas it was abundantly expressed in controls and RPC-Cx40ko. Conclusion: These data demonstrate that EC-specific deletion of Cx40 impairs conduction of endothelium-dependent dilations, however, per se does not increase blood pressure. Conversely, elevated pressure in RPC-Cx40ko does not affect such signal conduction along arterioles. Moreover, Cx40 seems to be a leading Cx for gap junction formation in EC.