[Search for the mechanoreceptor zones proper of the circulatory system in frogs]

In frogs anesthetized with viadril, intravenous injection of 2,5% dextran gives rise to inhibition of the sympathetic discharges in the renal nerve. Reduction in the blood volume causes an increase of the discharges in the renal nerve. The changes in the sympathetic activity are in a good agreement with those in the pulse pressure amplitude. Meanwhile no appreciable correlation is found between the changes in the sympathetic activity and the mean blood pressure. It is suggested that the intensity of the sympathetic activity in the frog renal nerve is mainly determined by the filling of the heart. After bilateral vagotomy the changes in the blood volume do not affect the electric activity of the renal nerve. The authors believe that the mechanoreceptor zones of the cardiovascular system responsible for its control are likely to be innervated only by the vagus.