Spinal localization of the intercostal motoneurones innervating the upper thoracic spaces.

At the rostral level of the thorax, the intercostal muscles participate both in postural and respiratory functions to a variable degree depending upon the considered muscle: external intercostal, intercartilaginous, internal intercostal, and triangularis sterni. In order to determine if these physiological properties are related to a special organization at the spinal cord level, we have used the retrograde transport of horseradish peroxidase as a tool for studying the spinal distribution of intercostal motor cells in the adult cat. Results suggest that the intercostal motoneurones could be distributed, in the ventral grey horn, among two areas according to the respiratory or postural muscle specialization.