Separation of descending spinal pathways to respiratory motoneurons

No dissociation could be demonstrated between the pathway mediating spontaneous inspiration and that serving the inspiratory response to stimulation of the medial reticular formation in the medulla, and the descending projection serving the abdominal muscle component of the cough response was separate from that serving spontaneous inspiration, and lay just ventral to the ventral horn.

Abstract

We have investigated in anesthetized and decerebrate cats the descending spinal pathways that respectively mediate spontaneous breathing, the inspiratory response to electrical stimulation of the medulla, and the cough response elicited by tracheolaryngeal stimulation. The effects of histologically defined, discrete cord lesions at the C1–2 level were assessed by measuring spontaneous and CO2-stimulated ventilation and the integrated EMG recorded bilaterally from diaphragm (inspiratory) and external abdominal oblique (expiratory) muscles. Bilateral lesions largely restricted to the ventral part of the lateral columns abolished spontaneous breathing. The pathways mediating the spontaneous drive to inspiratory and expiratory motoneurons appeared to be dissociated, the latter lying more medially in the ventral column. No dissociation could be demonstrated between the pathway mediating spontaneous inspiration and that serving the inspiratory response to stimulation of the medial reticular formation in the medulla. However, the descending projection serving the abdominal muscle component of the cough response was separate from that serving spontaneous inspiration, and lay just ventral to the ventral horn.