Sympathetic nerve stimulation induces frequency-dependent, slow contraction of the femoral artery in dogs, suggesting successive activation of smooth muscle layers via transmitter diffusion.
Femoral arterial diameter and pressure were measured in anesthetized dogs. Immediately after section of the ipsilateral lumbar sympathetic chain the artery dilated, reaching a maximum of 122.0% (±0.56 sem ) of resting diameter within 30 to 40 seconds. Later the diameter diminished, stabilizing at 104.3% (±1.8 sem ) of resting diameter within 15 minutes. Stimulation of the peripheral stump of the sympathetic chain induced frequency-dependent constriction, the frequency-response curve being hyperbolic. The average maximal response was 13.42% (± 1.19 sem ) of the resting diameter. These changes were not dependent on suprarenal secretion, blood flow, or changes in distal vascular bed resistance. The contraction of the artery was slow. The half-time of stabilized contraction was 21.6 seconds at a stimulus frequency of 1/sec and 36.8 seconds at 25/sec. The half-time of relaxation was shorter (10.7 seconds and 21.5 seconds, respectively) and also frequency-dependent. A significant dilatation, after stimulation, inversely proportional to the stimulation frequency, occurred after low-frequency stimulations. The time course of contraction suggests the activation of individual smooth muscle layers successively more remote to the nerve endings, possibly due to diffusion of transmitter liberated at the nerve endings by stimulation.
Gerová et al. (Sat,) studied this question.
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