Local and remote arteriolar dilations initiated by skeletal muscle contraction.

To investigate the relationship between skeletal muscle metabolism and arteriolar dilations in the region local to contracting muscle fibers as well as dilations at remote arteriolar regions upstream, we used a microelectrode on cremaster muscle of anesthetized hamsters to stimulate four to five muscle fibers lying approximately perpendicular to and overlapping a transverse arteriole. Before, during, and after muscle contraction, we measured the diameter of the arteriole at the site of muscle fiber overlap (local) and at a remote site approximately 1,000 microm upstream. Two minutes of 2-, 4-, or 8-Hz stimulation (5-10 V, 0.4-ms duration) produced a significant dilation locally (8.2 +/- 2.0-, 22.5 +/- 2.4-, and 30.9 +/- 2.1-microm increase, respectively) and at the remote site (4.2 +/- 0.8, 11.0 +/- 1.1, and 18.9 +/- 2.7 microm, respectively). Muscle contraction at 4 Hz initiated a remote dilation that was unaffected by 15-min micropipette application of either 2 microM tetrodotoxin, 0.07% halothane, or 40 microM 18-beta-glycyrrhetinic acid between the local and upstream site. Therefore, at the arteriolar level, muscle contraction initiates a robust remote dilation that does not appear to be transmitted via perivascular nerves or gap junctions.

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