Synaptic origin of the respiratory-modulated activity of laryngeal motoneurons

To determine the synaptic source of the respiratory-related activity of laryngeal motoneurons, spike-triggered averaging of the membrane potentials of laryngeal motoneurons was conducted using spikes of respiratory neurons located between the Bötzinger complex and the rostral ventral respiratory group as triggers in decerebrate, paralyzed cats. We identified one excitatory and two inhibitory sources for inspiratory laryngeal motoneurons, and two inhibitory sources for expiratory laryngeal motoneurons. In inspiratory laryngeal motoneurons, monosynaptic excitatory postsynaptic potentials were evoked by spikes of inspiratory neurons with augmenting firing patterns, and monosynaptic inhibitory postsynaptic potentials (IPSPs) were evoked by spikes of expiratory neurons with decrementing firing patterns and by spikes of inspiratory neurons with decrementing firing patterns. In expiratory laryngeal motoneurons, monosynaptic IPSPs were evoked by spikes of inspiratory neurons with decrementing firing patterns and by spikes of expiratory neurons with augmenting firing patterns. We conclude that various synaptic inputs from respiratory neurons contribute to shaping the respiratory-related trajectory of membrane potential of laryngeal motoneurons.