Identification of respiratory motor neurons in the carp and determination of their firing characteristics and interconnections

Abstract

Motor neurons of the respiratory muscles of the carp, located in the medulla oblongata, are identified with a signal averaging technique. Analysis of the firing characteristics of these neurons provides data on their activity patterns under different circumstances. The results show that, on the one hand, the number of spikes a motor neuron fires per respiratory cycle depends on the respiratory intensity, and can even be as low as one action potential per respiration. On the other hand, with constant respiratory intensity, the activity of individual motor neurons can stop and be resumed again in periods of several minutes. During mechanical loading of respiration, action potential synchronization between specific respiratory muscles takes place. Possible neuronal circuits causing this synchronization, which is thought to increase the coordination of the muscular effort, are discussed.