INTRACELLULAR POTENTIALS FROM RESPIRATORY NEURONES IN BRAIN-STEM OF CAT AND MECHANISM OF RHYTHMIC RESPIRATION

Abstract

The potential level at which action potentials were produced by 7 inspiratory and 1 expiratory neurones successfully penetrated was not the same throughout the burst of action potentials but shifted in the direction of depolarization as the burst progressed. Since temporal summation of synaptic potentials was the cause of each spike, the observed shift of the firing level implies that the excitability of respiratory neurones became less as the burst progressed. It is suggested that such a limiting factor plays a major role in periodically bringing the discharge of the neurone to an end. Rhythmicity would appear to result from the interplay of 3 factors: (a) self-reexciting and (b) self-limiting mechanisms within the inspiratory and the expiratory networks of neurones, and (c) reciprocal innervation of the 2 networks.