Transient vasodilatation in forearm on stimulation of carotid baroreceptors in man.

Carotid baroreceptor modulation of forearm vascular resistance was examined in 6 healthy subjects, each subject participating in 6 identical experimental runs. Forearm vascular resistance was calculated from simultaneous measurements of blood pressure and forearm blood flow (venous occlusion plethysmography). Carotid baroreceptor activity was modified by neck suction technique. To compare the effects of dynamic and static changes of baroreceptor activity neck suction was increased as a ramp lasting 6 s from -10 mm Hg (control) to -40 mm Hg and then maintained at this level. Measurements were started 15 s before and 9 s ('early') and 30 s ('late') after the onset of the suction ramp. Vascular resistance showed a significant (P less than 0.01) decrease during 'early' suction; but recovered partially and during 'late' suction there was no significant difference from control. The results indicate that carotid baroreceptors do modulate vascular resistance in the forearm and that the effect is more pronounced in response to dynamic than to static changes in baroreceptor input.