Coordinated diameter oscillations at arteriolar bifurcations in skeletal muscle.

The spontaneous rhythmical luminal changes (vasomotion) at bifurcations in the microvasculature of the rabbit tenuissimus muscle were investigated by means of a microscope video photometric system. Video scenes, containing two terminal arterioles originating from one transverse arteriole, showed that adjacent terminal arterioles constricted synchronously in 26 out of 31 contraction cycles. The onset of 60 constrictions in the parent transverse vessels was synchronized with the activity in terminal arterioles in 75% of the cycles and delayed in 25%. Vasomotion in the parent transverse vessels was notably smaller than in the terminal vessels. All the terminal arterioles in the different animals oscillated at the fundamental frequency of 18.9 +/- 3.5 cycles/min. We conclude that in the skeletal muscle microcirculation 1) coordinated spontaneous diameter oscillations occur in arterioles that are in proximity, 2) diameter changes are most pronounced in the terminal arterioles, and 3) coordinated vasomotion in this tissue exhibits a characteristic narrow band frequency. The presence of a microvascular pacemaker is hypothesized.