Remote Control of Respiratory Neural Network by Spinal Locomotor Generators

Jean-Patrick Le Gal,Didier Morin,Muriel Thoby-Brisson,Laura Cardoit,Laurent Juvin,Shawn Hochman

doi:10.1371/journal.pone.0089670

Abstract

During exercise and locomotion, breathing rate rapidly increases to meet the suddenly enhanced oxygen demand. The extent to which direct central interactions between the spinal networks controlling locomotion and the brainstem networks controlling breathing are involved in this rhythm modulation remains unknown. Here, we show that in isolated neonatal rat brainstem-spinal cord preparations, the increase in respiratory rate observed during fictive locomotion is associated with an increase in the excitability of pre-inspiratory neurons of the parafacial respiratory group (pFRG/Pre-I). In addition, this locomotion-induced respiratory rhythm modulation is prevented both by bilateral lesion of the pFRG region and by blockade of neurokinin 1 receptors in the brainstem. Thus, our results assign pFRG/Pre-I neurons a new role as elements of a previously undescribed pathway involved in the functional interaction between respiratory and locomotor networks, an interaction that also involves a substance P-dependent modulating mechanism requiring the activation of neurokinin 1 receptors. This neurogenic mechanism may take an active part in the increased respiratory rhythmicity produced at the onset and during episodes of locomotion in mammals.

Highlights

Upon initiation of exercise or locomotion, breathing rate rapidly increases in anticipation of the subsequent increased oxygen demand
It is noteworthy that in preparations showing a higher baseline respiratory rate (5 bursts/min), we previously reported that pharmacological activation of the lumbar cord still produced a significant 30% respiratory rhythm acceleration [16]
The results described in this report provide evidence indicating that lumbar locomotor pattern generators can participate to the modulation of respiratory network activity during episodes of locomotion

Summary

Introduction

Upon initiation of exercise or locomotion, breathing rate rapidly increases in anticipation of the subsequent increased oxygen demand. Central commands originating either from the hypothalamic [7,8], the mesencephalic [9], or the pontomedullary [10] locomotor region produce episodes of locomotion that are associated with a marked increase in respiratory activity. Such feedforward mechanisms efficiently contribute to the increase in ventilation during exercise

Methods

Results

Conclusion