Intercellular communication via gap junction channels (GJC) is reflected by conducted vasomotor responses. GJC in arterioles are composed of Cx40, 37, 45 and 43. It is unknown if Cx are interchangeable or exhibit specific properties to support cellular function. We investigated if Cx45, which exhibits a smaller conductance than Cx40, can functionally replace Cx40 using mice in which Cx45 is expressed in place of Cx40 (Cx40KI45). Propagation of dilations and constrictions initiated by acetylcholine (ACh) or KCl were studied in arterioles (~ 35 mm) by intravital microscopy in the cremaster muscle in Cx40-deficient (Cx40KO), Cx40KI45, and wildtype (wt) mice. ACh induced a similar dilation in all genotypes at the site of stimulation (64–69%). The dilation was conducted rapidly to distant sites in wt (54±8% at 1200mm). In Cx40KO this remote dilation was reduced to 29±4% (p<0.05). In Cx40KI45 remote dilations were impaired to a similar degree (22±6%). In contrast, the propagation of KCl-induced constrictions were comparable in all genotypes (local: -52 to -65%, 600mm: -24 to -25%). These data confirm the importance of Cx40 for the conduction of dilations. This function cannot be taken over by Cx45 expressed instead of Cx40 which suggests that specific Cx-properties are necessary to support conduction along the endothelium.