The contribution of muscarinic-receptor-mediated responses to epineurial vascular diameter at the sciatic nerve

This study used an anaesthetized rat model to directly observe changes in diameter of the vessels supplying the sciatic nerve in response to acetylcholine ([10.sup.-4] M), a muscarinic receptor agonist, and atropine ([10.sup.- 5] M), a muscarinic receptor antagonist. Topical application of acetylcholine resulted in increases in vessel diameter (baseline: 22.0 [+ or -] 2.5 [micro]m, acetylcholine: 28.8 [+ or -] 3.3 [micro]m), while topical application of atropine resulted in a decrease in diameter (baseline: 26.6 [+ or -] 3.2 [micro]m, atropine: 15.5 [+ or -] 3.6 [micro]m) of the epineurial vessels. Mean arterial pressure was not affected by either acetylcholine (baseline: 103.8 [+ or -] 1.8 mm Hg, acetylcholine: 102.8 [+ or -] 3.2 mm Hg) or atropine (baseline: 104.0 [+ or - ] 1.9 mm Hg, atropine: 105.2 [+ or -] 2.2 mm Hg). These data suggest that muscarinic-receptor-mediated responses can affect the diameter of the epineurial vessels at the sciatic nerve. In addition, muscarinic-receptor-mediated responses appear to contribute to baseline diameter of epineurial vessels at the sciatic nerve. Key words: sciatic nerve, epineurial vasculature, intravital microscopy, muscarinic receptor, acetylcholine, atropine. Dans cette etude, nous avons utilise un modele de rat anesthesie en vue d'observer directement les variations du diametre des vaisseaux alimentant le nerf sciatique en reaction a l'acetylcholine ([10.sup.-4] M), un agoniste des recepteurs muscariniques, et a l'atropine ([10.sup.-5] M), un antagoniste des recepteurs muscariniques. L'application topique d'acetylcholine a entraine une augmentation du diametre des vaisseaux de l'epinerve (depart: 22,0 [+ or -] 2,5 [micro]m, acetylcholine : 28,8 [+ or -] 3,3 [micro]m), tandis que l'application topique d'atropine a entraine leur diminution (depart: 26,6 [+ or -] 3,2 [micro]m, atropine : 15,5 [+ or -] 3,6 [micro]m). La tension arterielle moyenne n'etait pas affectee par l'acetylcholine (depart : 103,8 [+ or -] 1,8 mm Hg, acetylcholine : 102,8 [+ or -] 3,2 mm Hg) ni par l'atropine (depart : 104,0 [+ or -] 1,9 mm Hg, atropine : 105,2 [+ or -] 2,2 mm Hg). Ces donnees laissent entrevoir que des reactions mediees par les recepteurs muscariniques peuvent affecter le diametre des vaisseaux de l'epinerve du nerf sciatique. De plus, des reactions mediees par les recepteurs muscariniques semblent participer a l'etablissement du diametre de depart des vaisseaux de l'epinerve du nerf sciatique. [Traduit par la Redaction] Mots-cles: nerf sciatique, vaisseaux de l'epinerve, microscopie intravitale, recepteur muscarinique, acetylcholine, atropine.
Introduction To maintain proper function, the peripheral nerves require sufficient blood flow. Decreases in peripheral nerve blood flow have been associated with decreased nerve conduction velocity, nerve atrophy, and cell [...]