Abstract
Electrical dynamics of freshly isolated cerebral endothelium have not been determined independently of perivascular nerves and smooth muscle. We tested the hypothesis that endothelium of cerebral and skeletal muscle arteries differentially utilizes purinergic and muscarinic signaling pathways to activate endothelium-derived hyperpolarization. Changes in membrane potential (Vm) were recorded in intact endothelial tubes freshly isolated from posterior cerebral and superior epigastric arteries of male and female C57BL/6 mice (age: 3-8 months). Vm was measured in response to activation of purinergic (P2Y) and muscarinic (M3) receptors in addition to small- and intermediate-conductance Ca2+-activated K+ (SKCa/IKCa) and inward rectifying K+ (KIR) channels using ATP (100 μmol·L-1), acetylcholine (ACh; 10 μmol·L-1), NS309 (0.01-10 μmol·L-1), and 15 mmol·L-1 KCl, respectively. Intercellular coupling was demonstrated via transfer of propidium iodide dye and electrical current (±0.5-3 nA) through gap junctions. With similarities observed across gender, peak hyperpolarization to ATP and ACh in skeletal muscle endothelial tubes was ~twofold and ~sevenfold higher, respectively, vs cerebral endothelial tubes, whereas responses to NS309 were similar (from resting Vm ~-30 mV to maximum ~-80 mV). Hyperpolarization (~8 mV) occurred during 15 mmol·L-1 KCl treatment in cerebral but not skeletal muscle endothelial tubes. Despite weaker hyperpolarization during endothelial GPCR stimulation in cerebral vs skeletal muscle endothelium, the capability for robust SKCa/IKCa activity is preserved across brain and skeletal muscle. As vascular reactivity decreases with aging and cardiovascular disease, endothelial K+ channel activity may be calibrated to restore blood flow to respective organs regardless of gender.