Vasomotion and blood flow regulation in hamster skeletal muscle microcirculation: A theoretical and experimental study

A mathematical model of a microvasculature was used to study the effects of myogenic and flow-dependent stimuli on the characteristics of vasomotion a nd microvascular perfusion regulation. The model includes three branching o rders of arterioles derived from in vivo observations and incorporates a me chanism for terminal arteriolar closure during vasomotion. Simulations were performed to evaluate the effect of vasodilation and vasoconstriction on v asomotion pattern, and the changes in arteriolar effective diameter and flo w in response to arterial blood pressure variations triggering the regulato ry mechanisms. Vasomotion patterns were studied in the hamster cutaneous mu scle, visualized by fluorescent microscopy, in control conditions and after injection of acetylcholine (Ach) or NG-monomethyl-L-arginine (L-NMMA). We have found that vasomotion may be caused by different combinations of feedb ack mechanisms, including a strong rate-dependent myogenic response or a st rong now-dependent mechanism with no rate-dependent response. Decreasing th e rate-dependent component of the myogenic mechanism and increasing the tim e constant of the flow-dependent mechanism causes vessel stabilization and disappearance of vasomotion. In hamster microcirculation, Ach decreased vas omotion frequency and increased vasomotion amplitude and arteriolar effecti ve diameter, whereas L-NMMA caused a slight increase in vasomotion frequenc y and decrease in effective diameter. Model simulations, under dilatory and constrictory stimuli, confirmed these results. Moreover, the model predict ed that mean blood flow is maintained closer to normal despite arterial pre ssure changes (+/-15% flow changes versus +/-50% pressure variations) when the vessels were in nonoscillatory than when they are in oscillatory state. In conclusion, a large variety of vasomotion patterns affect arteriolar re sistance and microvessel perfusion in skeletal muscle. Furthermore, in the presence of vasomotion the network exhibits a poorer aptitude for regulatin g blood flow during arterial pressure changes (i.e., worse autoregulation) than the nonoscillatory network. (C) 1998 Academic Press.