Intracellular Ca²⁺ mediates a variety of vascular endothelial and smooth muscle cell functions. Smooth muscle cells (SMC) respond to biological activators with oscillatory and propagating rises in [Ca²⁺]_i that are highly organized in both time and space. Gap junctions (GJs) play a crucial role in the communication between vascular cells and in the synchronization of Ca²⁺ signals thereby tightly controlling the level of vasoconstriction. Before being incorporated into GJs, connexin (Cx) hemichannels reside in the plasma membrane in a closed state. Recent evidence suggests that hemichannels can be opened by various messengers and conditions, thereby forming a pore that allows the passage of ATP and ions. Using confocal microscopy and the Ca²⁺ sensitive dye Fluo-3, we examined the role of hemichannels in dynamic Ca²⁺ responses of SMC in intact acutely isolated small rat mesenteric arteries. Norepinephrine (3 mM) induced Ca²⁺ oscillations that were reduced in frequency by 98.4 % (p< 0.05) when exposed to carbenoxolone (50 mM), a none specific Cx channel inhibitor. Gap27 (200 mM), a Cx mimetic peptide that mainly blocks hemichannel responses (assayed by ATP release and dye uptake) after short incubation, reduced the spiking frequency by 96.4 % (p< 0.05). Suramin (200 mM) and PPADS (75 mM), two P2Y receptor antagonists, decreased the spiking frequency by 90.5 % (p<0.05) and 96.4% (p<0.01) respectively. Apyrase (5 U/ml), an enzyme that rapidly degrades extracellular ATP, reduced the spiking frequency by 71.4% (p<0.01). None of these agents affected the amplitude of the Ca²⁺ oscillations. Our results suggest a role for Cx hemichannels and purinergic signaling in Ca²⁺ oscillations of SMC stimulated with norepinephrine. Further work will be directed to assess the involvement of these signaling partners in contractile responses of these vessels.