Figure 2.

TRPM4 inhibitor 9-phenanthrol completely antagonized myogenic tone and both norepinephrine and KCl evoked vasoconstrictions. Pressure myography of rat skeletal muscle (A–C) and mesenteric (D,E) arteries was performed. Basilar arteries (F) were tested on an isometric force measurement system. (A) Myogenic tone was allowed to develop at 80 mmHg intraluminal pressure (first symbol: before, second symbol: after myogenic tone development), then 9-phenanthrol was added to the organ bath at the indicated concentrations. (B) Myogenic tone was first assessed in the presence of Ca²⁺ on skeletal muscle arterioles by increasing intraluminal pressure in 20 mmHg increments from 20 mmHg to 120 mmHg. Vessels were then incubated with 100 µM 9-phenanthrol and the same procedure was repeated. Vessels were then thoroughly washed, and diameter was also recorded in the absence of Ca²⁺. (C) Skeletal muscle arterioles were preconstricted with 10 µM norepinephrine (first symbol: before, second symbol: after norepinephrine, NE); then, 9-phenanthrol was added to the organ bath at the indicated concentrations. (D) Mesenteric arteries were preconstricted with 10 µM norepinephrine (first symbol: before, second symbol: after norepinephrine, NE); then, 9-phenanthrol was added to the organ bath at the indicated concentrations. (E) Mesenteric arteries were preconstricted with 80 mM KCl; then, 9-phenanthrol was added to the organ bath. (F) Basilar arteries were preconstricted with 80 mM KCl; then, 9-phenanthrol was added to the organ bath. Graphs show the mean ± SEM. Significant differences (p < 0.05) from the initial diameter (panels A,C,D) or from the diameter in the presence of Ca²⁺ (Panel B) are labeled by the asterisks (*). Five (n = 5) animals were used for each panels (A–E), while four animals were used for panel (F).