Abstract
The heart has been used as a convenient tool of physiological and pharmacological studies of nerves and muscles. The present experiment was done in rabbit's heart as a possible preparation to be isolated with the sympathetic nerve in a convenient experimental animal. At the beginning of the present experiment, investigation was done as to whether or not there was a relationship between positive mechanical responses to and noradrenaline output released by the sympathetic nerve stimulation. Effects of high concentrations of external Ca++ and Mg++, cocaine and adrenergic β-blockers on noradrenaline output released by the sympathetic nerve stimulation were re-investigated.
The objective of this paper is to discuss the possibility of the existence of intracardiac sympathetic ganglia. Such a hypothesis was based mainly on observations that in heart tissues nicotinic drugs exerted effects like those of the sympathetic nerve stimulation, which could be blocked by ganglionic blocking agents (1-4). The hypothesis appeared open to discussion under evidence (5-7). On the other hand, Juhász-Nagy and Szentiványi (8) and Takenaka et al. (9) have demonstrated the possibility that vasoconstrictor fibers of coronary arteries synapse with ganglion cells in or near the wall of the dog's heart. In the present paper, it was attempted to throw light on the problem by investigation of effects of hexamethonium on mechanical and coronary responses to and noradrenaline output released by the electrical stimulation of the sympathetic nerve in the rabbit's heart. Preliminary reports have already been published (10).
