CENTRAL EXCITATION AND INHIBITION IN REFLEX CHANGES OF HEART RATE

Abstract

Reflex changes of heart rate on afferent maximal stimulation at varying frequencies of the depressor, the left vagus, and the sciatic were recorded from cats with either the vagi or the accelerators severed. These responses were compared with those obtained from peripheral maximal stimulation at varying frequencies of either the right vagus or the right accelerators. The subsidence of central excitation and inhibition in these reflexes may be very long (up to 10 min.). The maximum of the reflex responses at equilibrium is a continuous function of the frequency of afferent stimulation. The reflex output of the centers is directly proportional to the excitatory input. For a given degree of tonic activity, the output is a continuous, smooth, non-linear function of the inhibitory input. The duration of the subsidence of the reflex responses is a continuous function of the afferent frequency. It is concluded that reverberating delay paths do not explain after-discharge satisfactorily while a chemical hypothesis is adequate.