Sustained conduction of vasomotor responses in rat mesenteric arteries in a two-compartment in vitro set-up

Aim: Conduction of vasomotor responses may contribute to long-term regulation of resistance artery function and structure. Most previous studies have addressed conduction of vasoactivity only during very brief stimulations. We developed a novel set-up that allows the local pharmacological stimulation of arteries in vitro for extended periods of time and studied the conduction of vasomotor responses in rat mesenteric arteries under those conditions.

Methods: The new in vitro set-up was based on the pressure myograph. The superfusion chamber was divided halfway along the vessel into two compartments, allowing an independent superfusion of the arterial segment in each compartment. Local and remote cumulative concentration-response curves were obtained for a range of vasoactive agents. Additional experiments were performed with the gap junction inhibitor 18β-glycyrrhetinic acid and in absence of the endothelium.

Results: Phenylephrine-induced constriction and acetylcholine-induced dilation were conducted over a measured distance up to 2.84 mm, and this conduction was maintained for 5 minutes. Conduction of acetylcholine-induced dilation was inhibited by 18β-glycyrrhetinic acid, and conduction of phenylephrine-induced constriction was abolished in absence of the endothelium. Constriction in response to high K⁺ was not conducted. Absence of remote stimulation dampened the local response to phenylephrine.

Conclusion: This study demonstrates maintained conduction of vasoactive responses to physiological agonists in rat mesenteric small arteries likely via gap junctions and endothelial cells, providing a possible mechanism for the sustained functional and structural control of arterial networks.