Intravital investigation of rat mesenteric small artery tone and blood flow

Abstract

Functional characteristics of rat mesenteric small arteries (internal diameter ∼150-200 μm) have been extensively studied in vitro using isometric and isobaric myographs. In vivo, precapillary arterioles (internal diameter < 50 μm) have been studied, but only a few studies have investigated the function of mesenteric small arteries. We here present a novel approach for intravital studies of rat mesenteric small artery segments (∼5 mm long) isolated in a chamber. The agonist-induced changes in arterial diameter and blood flow were studied using video imaging and laser speckle analysis in rats anaesthetized by isoflurane, pentobarbital, ketamine-xylazine, or by a combination of fentanyl, fluanison and midazolam (rodent mixture). The arteries had spontaneous tone. Noradrenaline added to the chamber constricted the artery in the chamber but not the downstream arteries in the intestinal wall. The constriction was smaller when rats were anaesthetized by rodent mixture in comparison with other anaesthetics, where responses were qualitatively similar to those reported in vitro. The contraction was associated with reduction of blood flow, but no flow reduction was seen in the downstream arteries in the intestinal wall. The magnitude of different endothelium-dependent relaxation pathways was dependent on the anaesthesia. Vasomotion was present under all forms of anaesthesia with characteristics similar to in vitro. We have established an intravital method for studying the tone and flow in rat mesenteric arteries. The reactivity of the arteries was qualitatively similar to the responses previously obtained under in vitro conditions, but the choice of anaesthetic affects the magnitude of responses.

High Sodium Intake Impairs Small Artery Vasoreactivity in vivo in Dahl Salt-Sensitive Rats

“…In an intravital investigation of different anesthetic methods [24], the reactivity of the small arteries was qualitatively similar to the responses previously obtained in vitro. In an in vitro study [25], the vasodilatation of mesenteric arteries induced by ACh in low-sodium-fed rats was similar to that in high-sodium-fed rats.…”

Rat mesenteric small artery neurogenic dilatation is predominantly mediated by β1‐adrenoceptors in vivo

“…With this set‐up, there is minimal interferences from changes in perfusion parameters and movement of the intestine when the drugs are applied (Nyvad et al . ). Our previous study (Nyvad et al .…”

“…Additional anaesthesia was supplied s.c. based on reaction to toe pinching throughout the experiment (Nyvad et al . ).…”

“…The relative vasoconstriction was calculated as [( D B – D C )/ D B ] × 100%, where D C is the inner diameter in the presence of vasoconstrictor and D B is the inner diameter at the basal tone (Nyvad et al . ). EFS‐induced vasodilatation in response to EFS was expressed as (Fig.…”

“…In the present study, we have assessed the relative importance of β‐adrenoceptors and CGRP for nerve‐induced vasodilatation in rat mesenteric small arteries in vivo using a novel experimental set‐up (Nyvad et al . ). By contrast to the findings of Kawasaki and coworkers (Kawasaki et al .…”