Spiking behavior and membrane potential trajectories of pre‐BötC and hypoglossal neurons recorded from the rat in situ

Abstract

Cellular and synaptic mechanisms operating in the brainstem respiratory network are not completely understood. Embedded in the respiratory network, the pre-Botzinger complex (pre-BötC) receives convergent inputs from numerous neuron populations. Hypoglossal motoneurons (XII MNs) are a major cranial motor output of the respiratory network and their activation during breathing, including by pre-BötC-driven circuits, is essential for maintaining upper airway patency. We applied sharp microelectrode intracellular recording techniques to characterize pre-BötC neuron and XII MN respiratory spiking patterns and input synaptic drives within in situ perfused brainstem-spinal cord preparations of mature rats, which allow analysis of patterning mechanisms during inspiratory and expiratory phases in an intact brainstem. A population of pre-BötC inspiratory neurons showed post-inspiratory hyperpolarization followed by ramping membrane potential and excitatory synaptic drive with characteristic pre-inspiratory spiking activity. In the XII motor nucleus we distinguished three groups of respiratory MNs by their spiking profile (including pre-inspiratory spiking) and membrane potential time course during the respiratory cycle. Our data suggest multiple pattern formation mechanisms and sources of synaptic drive shaping membrane potential trajectories of pre-BötC neurons and XII MNs in situ.