抄録
The overall changes in heart rate (HR) during 24-hour period has a positive relationship with arterial pressure (AP), suggesting that the changes in HR is controlled not by the arterial baroreflex but by a central feedforward signal (termed central command) coupled with daily activities. It has been reported that the positive AP-HR relationship is lost in idiopathetic Parkinson's disease patients. We hypothesized that the midbrain dopaminergic system may play a role in producing central command for autonomic control of cardiac rhythm. To solve this, we attempted to 1) study the effect of stimulation of the dopaminergic neurons on HR, AP, and femoral or brachial blood flow in anesthetized animals, 2) to determine the effects of lesion of the neurons on the cardiovascular responses during locomotion in conscious animals, and 3) to compare the cardiovascular responses during voluntary handgrip exercise, walking, and postural changes in normal and Parkinson's disease subjects. The stimulation of the midbrain ventral tegmental area (VTA), but not substantia nigra (SN), caused an increase in limb blood flow, indicating vasodilation of muscle blood vessels. VTA lesion blunted the centrally-induced cardiovascular responses at the onset of locomotion. Similarly, we observed attenuated cardiovascular responses during handgrip exercise, walking, and postural changes in idiopathetic Parkinson's disease patients. These results suggest that dopaminergic neurons in the midbrain may produce central commands for the cardiovascular adaptation during exercise. [Jpn J Physiol 54 Suppl:S25 (2004)]
