Cardiac Sympathetic Nerves in Rats: Anatomical and Functional Features

抄録

Anatomical pathways and natures of reflex as well as spontaneous activities of cardiac sympathetic nerves (CNs) were investigated in rats.
2. Anatomically, the stellate CNs on both sides provide a major sympathetic supply to the rat heart with additional contribution of the thoracic CNs on the left side.
3. Functions of these CNs were studied in chloralose-urethane anesthetized and artificially ventilated rats. Electrical stimulation of these CNs produced an increase in heart rate and a rise in blood pressure. The increase in heart rate was more potent on the right-side stimulation, while the rise in blood pressure was greater on the left-side stimulation.
4. Stimulation of the aortic depressor nerve (ADN) inhibited spontaneous discharges of the CN for a longer period as compared with those of the cervical postganglionic sympathetic nerve (CSN). On the other hand, stimulation of the sural nerve produced a longer lasting reflex increase in discharges of the CN as compared with that of the CSN. These findings suggest that cardioregulatory sympathetic outflow is more affected by visceral and somatosensory input than is the other sympathetic outflows.
5. Spontaneous discharges of both nerves showed a rhythmicity associated with heart beats. Although the magnitude of this rhythmicity was not clearly different between these two nerves, the time from bottom to peak firing level of the phasic discharges of the CN was significantly longer than that of the CSN. This finding is consistent with the longer lasting effect of the ADN stimulation on the CN discharges.