Functional changes in ventricular muscle after crushing the sinoauricular node

Abstract

The influence of changes of imposed rhythm and/or crushing of the sinoauricular node on the total cholinesterase activity and excitability cycle of the ventricular muscle has been investigated. Experiments were performed on rabbits anesthetized with chloralose (0.1 g/kg). A potentiometric titration method was applied for the estimation of cholinesterase activity. Acetylcholine bromide was used as a substrate. The strength-interval curves of the right ventricle driven in situ at various rates were recorded. Crushing the sinoauricular node was followed by a decrease in cholinesterase activity, if the heart was driven at a rhythm exceeding the spontaneou rate by 100 beats/min. Destruction of the node was followeds also by shortening of the absolute refractory period if the accelerated driving lasted for at least 20 min. It is supposed that the acetylcholine metabolism in rabbit ventricular muscle is influenced by the activity of the cardiac conductive system.