[Pharmacological analysis of sinus rhythm].

The SA nodal pacemaker activity is regulated dominantly by autonomic nervous elements, i.e., sympathetic and parasympathetic nervous factors. In addition, circulatory bioactive substances and physicochemical factors also modify changes in sinus rate. Exogenously applied substances exert their actions on sinus rate directly and/or indirectly. The mechanisms of bradycardia and tachycardia induced by electrical nerve stimulation or exogenous substances are reviewed mostly by describing the results from experiments in isolated canine SA node preparations which were perfused with blood. In this review, newly developed bradycardic agents are introduced in addition to descriptions of numerous active substances developed in the past.