Functional Interactions between Mammalian Respiratory Rhythmogenic and Premotor Circuitry

Area of Science:

• Neuroscience
• Computational Biology
• Respiratory Physiology

Background:

• Breathing control in mammals originates from the preBötzinger complex (preBötC) and associated premotor networks.
• Dbx1-expressing neurons (Dbx1 neurons) are crucial components of both the preBötC rhythm generator and premotor circuits.
• The precise structure and function of these Dbx1-derived neural networks remain incompletely understood.

Purpose of the Study:

• To investigate the structural and functional organization of respiratory rhythm and pattern-generating circuits.
• To identify network configurations that can replicate experimental findings from cell-specific laser ablation studies.
• To propose a feasible model for Dbx1-derived interneuron circuits involved in mammalian breathing.

Main Methods:

• Utilized a slice model of breathing incorporating the preBötC, hypoglossal (XII) motor nucleus, and XII premotor circuits.
• Employed a cell-specific laser ablation system to selectively remove Dbx1 neurons in the preBötC and premotor regions.
• Developed and coupled a computational model of the preBötC with premotor network configurations for in silico simulations.

Main Results:

• Cumulative ablation of Dbx1 preBötC neurons significantly reduced and eventually terminated XII motor output and respiratory rhythm.
• Ablation of Dbx1 premotor neurons decreased motor output but did not affect respiratory frequency or rhythm termination.
• A computational model accurately replicated experimental results when the premotor network was configured as a 'small-world' network with balanced synaptic input.

Conclusions:

• The 'small-world' network topology, with balanced synaptic input from the preBötC, provides a viable model for respiratory premotor circuits.
• This study offers a framework for understanding the fundamental structure and function of mammalian respiratory rhythm and pattern generators.
• The findings generate experimentally testable predictions regarding the organization of Dbx1-derived neural circuits in the brainstem.