ABSTRACT
The reflex mechanisms of the responses in heart rate elicited by acupuncture stimulation in anesthetized rats were examined. An acupuncture needle measuring 160μmin diameter was inserted into skin and the underlying muscles to the hindlimb to a depth of about 5mm and was twisted once every second for 1min. A decrease in the heart rate was observed in 55% of 22 trials and in 70% of 20 trials when muscles separated from the overlying skin were stimulated. The response was abolished completely by cutting the femoral and sciatic nerves. The response was not influenced by transecting of the bilateral vagi but was totally abolished by transecting of the cardiac sympathetic nerves. Therefore, we conclude that the decrease in heart rate elicited by acupuncture stimulation of a hindlimb is based on a somato-autonomic reflex, in which the afferent pathway is composed of hindlimb muscle afferents and the efferent pathway is composed of cardiac sympathetic nerves.