Résumé : Connexins form gap-junctions (GJs) that directly connect cells, thereby coordinating vascular cell function and controlling vessel diameter and blood flow. GJs are composed of two hemichannels contributed by each of the connecting cells. Hemichannels also exist as non-junctional channels that, when open, lead to the entry/loss of ions and the escape of ATP. Here we investigated cross-talk between hemichannels and Ca(2+)/purinergic signalling in controlling blood vessel contraction. We hypothesized that hemichannel Ca(2+ )entry and ATP release contributes to smooth muscle cell (SMC) Ca(2+ )dynamics, thereby influencing vessel contractility. We applied several peptide modulators of hemichannel function and inhibitors of Ca(2+ )and ATP signalling to investigate their influence on SMC Ca(2+ )dynamics and vessel contractility.