4-Aminopyridine attenuates endothelium-derived hyperpolarizing factor-induced hyperpolarization and relaxation of rat mesenteric small arteries (part 2)
ANIMALS AND METHODS
Dissection and mounting: Male Wistar rats (150 to 200 g) were killed by dislocation of the cervical spinal column. Part of the intestinal tract with its feeding vasculature was removed and stored in a physiological salt solution (PSS) containing, in mM, NaCl 125, KCl 4.7, MgSO4 1.17, NaH2PO4 1.2, CaCl2 3.0, HEPES 3.0, EDTA 0.029, glucose 5.0 (pH 7.4). Ring segments from the second- or third-order branch of the mesenteric superior artery (internal diameter 180 to 250 |j.m) were dissected and transferred to the chamber of a dual myograph (Model 410A, JP Trading, Aarhus, Denmark) chamber.Thereafter two vascular segments were threaded on 40 |j.m diameter stainless steel wires and mounted on the myograph. The endothelium lining of the ring segments was removed when required by rubbing the lumen with a small roughened wire. Removal of the endothelium was deemed to be successful if hyperpolarization and relaxation did not occur following application of the high concentration (10-4 M) of carbachol. After the temperature reached 37°C, the vessels were stretched radially to their optimal lumen diameter . After a 30 min equilibration, reactivity of the vessels was tested with K-PSS (150 mM) containing noradrenaline (10 ^M). The best online pharmacy that deserves your trust and gives you best quality order alegra that you will always appreciate, not to mention all the other services available.
In conclusion, 4-AP completely blocks carbachol-induced nitric oxide- and prostanoid-resistant hyperpolarization of SMC and relaxation of the vascular wall of rat mesenteric arteries. We propose that delayed rectifier potassium currents are responsible for EDHF-induced hyperpolarization of SMC and subsequent relaxation of small vascular branches isolated from rat mesenteric arteries.