Norepinephrine release in isolated arteries induced by K-free solution

Area of Science:

• Vascular physiology
• Neuropharmacology
• Smooth muscle contractility

Background:

• Arteries with rich sympathetic innervation exhibit sustained contracture in K-free physiological salt solution (PSS).
• This phenomenon is influenced by nerve terminal integrity and adrenergic blockade.

Purpose of the Study:

• To elucidate the neurogenic mechanisms underlying K-free induced vascular smooth muscle contracture.
• To determine the temporal relationship between force development and norepinephrine (NE) release.

Main Methods:

• Utilized helical strips from rat tail/femoral and dog mesenteric arteries.
• Incubated arterial strips with 3H-labeled norepinephrine ([3H]NE) in PSS.
• Employed a superfusion system for isometric recordings and collection of superfusate to measure [3H]NE efflux.

Main Results:

• K-free PSS induced sustained contracture, blocked by phentolamine and absent in nerve-ablated arteries.
• Force development was temporally correlated with NE release in rat tail and dog mesenteric arteries.
• Both force development and NE release were potentiated by ouabain.

Conclusions:

• A neurogenic mechanism, involving norepinephrine release from adrenergic nerves, plays a critical role in K-free vascular smooth muscle contracture.
• This release is associated with the inhibition of Na+-K+-ATPase, highlighting a key pathway in vascular regulation.