Effects of ischemia and myogenic activity on active and passive mechanical properties of rat cerebral arteries.
Passive (papaverine induced) and active (spontaneous pressure induced) biomechanical properties of ischemic and nonischemic rat middle cerebral arteries (MCAs) were studied under pressurized conditions in vitro. Ischemic (1 h of occlusion), contralateral, and sham-operated control MCAs were isolated from male Wistar rats (n = 22) and pressurized using an arteriograph system that allowed control of transmural pressure (TMP) and measurement of lumen diameter and wall thickness. Three mechanical stiffness parameters were computed: overall passive stiffness (beta), pressure-dependent modulus changes (E(inc,p)), and smooth muscle cell (SMC) activity-dependent changes (E(inc,a)). The beta-value for ischemic vessels was increased compared with sham vessels (13.9 +/- 1.7 vs. 9.1 +/- 1.4, P < 0.05), indicating possible short-term remodeling due to ischemia. E(inc,p) increased with pressure in the passive vessels (P < 0.05) but remained relatively constant in the active vessels for all vessel types, indicating that pressure-induced SMC contractile activity (i.e., myogenic reactivity) in cerebral arteries leads to the maintenance of a constant elastic modulus within the autoregulatory pressure range. E(inc,a) increased with pressure for all conditions, signifying that changes in stiffness are influenced by SMC activity and vascular tone.
Coulson
Rebecca J
RJ
Department of Mechanical Engineering and Department of Neurology, The University of Vermont, Burlington 05405, USA.
Chesler
Naomi C
NC
Vitullo
Lisa
L
Cipolla
Marilyn J
MJ
D000818:Animals; D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology; D004195:Disease Models, Animal; D004548:Elasticity / Q000187:drug effects; D066298:In Vitro Techniques; D002546:Ischemic Attack, Transient / Q000503:physiopathology*; D008297:Male; D020768:Middle Cerebral Artery / Q000187:drug effects / Q000503:physiopathology*; D009129:Muscle Tonus / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology; D010208:Papaverine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D014654:Vascular Patency; D014661:Vasoconstriction / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D010208:Papaverine