Acetylcholine-induced relaxation of rabbit facial artery after occlusion

Objectives: The aim of this study was to investigate the influence of unilateral carotid artery occlusion on both: acetylcholine-induced vasorelaxation of rabbit facial artery and underlined mechanism of this acetylcholine effect.

Method: In organ bath studies with rings of rabbit facial artery, main feed artery for submandibular gland, changes in isometric tension were recorded before and after 10-, 30- and 60-minutes long common carotid artery occlusion by cords. Relaxation was studied in vascular segments precontracted with phenylephrine (10µM).

Results: In arterial segments obtained from the contralateral side of occlusion (control), acetylcholine induced concentration- and endothelium-dependent relaxation with maximal response 110, 0 ± 5,5 % (n=10). In the arterial segments of rabbit facial artery on the ipsilateral side of occlusion, the relaxant effect of acetylcholine, after 10 minutes of occlusion of carotid artery, was not significantly changed, while 30- and 60-minutes long occlusion significantly reduced vasorelaxation (112,2 ± 4,5% vs. 82,5 ± 6,7% and 102,5 ±6,2% vs. 67,5 ± 5,0, respectively), Also, the inhibitory effects of L-NOARG, nonselective inhibitor of NOS, and indomethacin, nonselective inhibitor of COX, on acetylcholine-induced vasorelaxation, were potentiated after 30- and 60-minutes long occlusion with respect to control rings.

Conclusions: These results suggest that common carotid artery occlusion causes significant and time-dependent reduction of acetylcholine-induced vasorelaxation of rabbit facial artery and that this effect was probably mediated by alterations in endothelial NO and prostacyclin release.