Do cholinergic nerves innervating rat mesenteric arteries regulate vascular tone?

Area of Science:

• Vascular Biology
• Neuroscience
• Pharmacology

Background:

• Vascular blood vessels contain cholinergic acetylcholine receptors (AChR), but the source of acetylcholine (ACh) remains unconfirmed.
• Rat mesenteric arteries are innervated by perivascular adrenergic and calcitonin gene-related peptide (CGRP)-containing nerves, which modulate vascular tone.
• The functional role of cholinergic innervation in vascular tone regulation is currently unknown.

Purpose of the Study:

• To investigate the presence and function of cholinergic innervation in rat mesenteric arteries.
• To determine if cholinergic nerves influence adrenergic-mediated vasoconstriction or CGRPergic-mediated vasodilation.
• To characterize the nature of cholinergic innervation in relation to other nerve types.

Main Methods:

• Experiments were conducted on rat mesenteric vascular beds without endothelium.
• Pharmacological agents including cholinesterase inhibitor (neostigmine), muscarinic antagonist (atropine), and nicotinic antagonist (hexamethonium) were used.
• Perivascular nerve stimulation (PNS) and exogenous vasoactive agents were applied.
• Capsaicin (CGRP depletor) and nitric oxide synthase inhibitor were utilized.
• Immunohistochemistry for choline acetyltransferase was performed.

Main Results:

• Cholinergic agents did not affect adrenergic nerve-mediated vasoconstriction induced by PNS or norepinephrine.
• Cholinergic agents did not alter CGRPergic nerve-mediated vasodilation induced by PNS.
• Immunohistochemistry revealed choline acetyltransferase-positive fibers resistant to capsaicin and adrenergic toxins, indicating a distinct cholinergic innervation.

Conclusions:

• Rat mesenteric arteries possess a distinct cholinergic innervation separate from adrenergic and capsaicin-sensitive nerves.
• This cholinergic innervation does not appear to play a significant role in regulating vascular tone in the rat mesenteric arterial bed.
• The precise function of this identified cholinergic innervation warrants further investigation.