Persistent activity and interactions in the brainstem respiratory network during hyperventilatory apnea

Abstract

Brainstem respiratory neuron interactions during hyperventilatory apnea (HA) and the dissolution and reemergence of the motor pattern for breathing remain poorly understood. We used multi‐array recording, cross‐correlation, and gravity clustering methods to evaluate spike train data from the ventral respiratory column (VRC), pontine respiratory group, and medullary raphé nuclei of decerebrate vagotomized neuromuscularly‐blocked cats. Phrenic activity, blood pressure, end‐tidal CO2, and arterial blood gas measures of O2, CO2 and pH were monitored. During HA: (i) tonic activities persisted in subsets of VRC inspiratory (I) and expiratory (E) neurons; (ii) short‐time scale correlations indicated interactions among neurons that expressed E and non‐respiratory modulated discharge patterns during control conditions, including neurons with functional inhibitory actions on I neurons; (iii) selective stimulation of carotid chemoreceptors by close injection of CO2‐saturated saline transiently evoked rhythmic respiratory network activity and suppressed tonic E neuron activity; (iv) respiratory and slower (0.04 – 0.1 Hz) network oscillations were disrupted. We conclude that VRC tonic E neurons contribute to I drive inhibition during HA (cf. Sears et al. 1982) and document the loss of multiple rhythms during HA. Support: NIH grant NS19814