A new preparation of rat extensor digitorum longus muscle for intravital investigation of the microcirculation.

The extensor digitorum longus (EDL) muscle is a fast contracting muscle with 60% of Type IIB fibres at the surface. We developed a surgical procedure for exposing this surface from which the microcirculation can be visualized via intravital microscopy. From video recorded microscopic images we determined that microvascular perfusion at the surface is fairly stable for at least 5 hours. Among 7 anaesthetized rats (male Wistar), the density of perfused capillaries decreased at a rate of 4% per hr. The average velocity of red cells in perfused capillaries remained constant at 0.14 mm/s. In order to demonstrate the usefulness of the preparation we report 2 sample experiments involving muscle contraction and aging. The major advantages of EDL preparation are (1) absence of mechanical manipulation of the muscle during exposure, (2) no requirement for surface superfusion following exposure, and (3) independence of the visibility of the microcirculation from rat size and age.