Abstract
The effects of acupuncture-like stimulation of a hindlimb on heart rate were examined in anesthetized rats. An acupuncture needle, having a diameter of either 160 or 340 µm, was inserted into the skin and underlying muscles at a depth of about 5 mm and twisted right and left twice every second for 1 min. Stimulation by a needle with diameter of either 160 or 340 µm produced a decrease in heart rate. Severance of the femoral and sciatic nerves ipsilateral to the hindlimb stimulation completely abolished the bradycardiac response. In addition, heart rate was significantly decreased by acupuncture-like stimulation of the hindlimb muscles alone, but was not significantly influenced by stimulation of the hindlimb skin alone. The bradycardiac response induced by acupuncture-like stimulation was not influenced by bilateral severance of the vagal nerves at the cervical level, but was abolished by bilateral stellectomy. Acupuncture-like stimulation of the hindlimb induced a decrease in the activity of the cardiac sympathetic efferent nerve as well as decrease in heart rate. These results indicate that the decrease in heart rate induced by acupuncture-like stimulation of a hindlimb is a reflex response. The afferent pathway is composed of hindlimb muscle afferents while the efferent pathway is composed of cardiac sympathetic nerves.
