The inner diameter and wall thickness of rat middle cerebral arteries (MCAs) were measured in vitro in both a pressure-induced, myogenically-active state and a drug-induced, passive state to quantify active and passive mechanical behavior. Elasticity parameters from the literature (stiffness derived from an exponential pressure-diameter relationship, β, and elasticity in response to an increment in pressure, Einc-p) and a novel elasticity parameter in response to smooth muscle cell (SMC) activation, Einc-a, were calculated. β for all passive MCAs was 9.11±1.07 but could not be calculated for active vessels. The incremental stiffness increased significantly with pressure in passive vessels; Einc-p 106 dynes/cm2 increased from 5.6±0.5 at 75 mmHg to 14.7±2.4 at 125 mmHg, (p<0.05). In active vessels, Einc-p 106 dynes/cm2 remained relatively constant (5.5±2.4 at 75 mmHg and 6.2±1.0 at 125 mmHg). Einc-a 106 dynes/cm2 increased significantly with pressure (from 15.1±2.3 at 75 mmHg to 49.4±12.6 at 125 mmHg, p<0.001), indicating a greater contribution of SMC activity to vessel wall stiffness at higher pressures.

Issue Section:
Technical Papers
Keywords:
cardiovascular system, blood vessels, haemodynamics, brain, muscle, biomechanics, elasticity, neurophysiology
Topics:
Cerebral arteries, Pressure, Surface mount components, Vessels, Mechanical properties, Muscle, Stiffness
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