Structural changes and in situ aortic pressure-diameter relationship in long-term chemical-sympathectomized rats.
This study determined the effects of long-term chemical sympathectomy with guanethidine (GN) on the mechanical properties and composition of the distal abdominal aorta in Wistar rats. GN was daily administered for 3 mo (3M-GN, from 1 to 12 wk), 5 wk (5W-GN, from 7 to 12 wk), and 8 days (8D-GN, from 11 to 12 wk). All experiments were performed at 12 wk of age to avoid age differences at examination. We used a high-resolution echo-tracking system to determine in situ, in the systolic-diastolic range, the aortic diameter-, compliance-, and distensibility-pressure curves in anesthetized rats. We observed an equivalent significant fall in the tyramine pressor response in all conscious GN-treated rats. Blood pressure was not affected by sympathectomy after 8 days and 5 wk of treatment but was significantly reduced in 3M-GN rats. Chronic sympathetic denervation increased aortic diameter and compliance in 8D-GN rats, compared with those obtained at the same distending pressure in control rats, suggesting vascular smooth muscle relaxation. In contrast, in 5W-GN and 3M-GN rats, the distensibility pressure-curves were significantly shifted toward lower levels of distensibility and pressure, indicating a decreased aortic distensibility at the same level of arterial pressure. Sympathectomy produced a significant reduction in the content of elastin, one of the most distensible components of the arterial wall in 5W-GN and 3M-GN rats. These results suggest that intact sympathetic nerves are necessary to maintain normal functional and structural properties of large arteries in rat. The reduction in aortic distensibility, in long-term sympathectomized rats, could have resulted from complex interactions between local aortic denervation, change in the set point of distending pressure, and changes in aortic smooth muscle tone and/or wall composition.
Lacolley
P
P
Department of Pharmacology, Institut National de la Santé et de la Recherche Médicale U. 337, Paris, France.
Glaser
E
E
Challande
P
P
Boutouyrie
P
P
Mignot
J P
JP
Duriez
M
M
Levy
B
B
Safar
M
M
Laurent
S
S
D000818:Animals; D001011:Aorta / Q000294:innervation* / Q000502:physiology*; D001794:Blood Pressure; D003187:Compliance; D004549:Elastin / Q000378:metabolism; D006145:Guanethidine; D006339:Heart Rate; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013563:Sympathectomy, Chemical; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D014661:Vasoconstriction; D014664:Vasodilation
D004549:Elastin; D006145:Guanethidine