THE SEGMENTAL REFLEX RELATIONS OF CUTANEOUS AFFERENT INFLOW TO THORACIC RESPIRATORY MOTONEURONS

Abstract

Recording from individual dorsal root fibers subserving cutaneous sensations of thoracic wall, as well as recordings from muscle fibers of internal and external intercostal muscles, were obtained from unanesthetized, spinalized and from anesthetized cats. Average cutaneous receptive fields for 144 afferent fibers was 53 mm. Excitatory reflexogenic fields for 29 expiratory and 32 inspiratory intercostal muscle fibers were 51 and 67 cm respectively. Respiratory muscle fibers showed cutoff and/or equilibrating behavior during repetitive stimulation of cutaneous field at rates less than 15/sec; afferent fibers did not. Available evidence suggests participation of internuncial neurons in reflex regulation of spinal respiratory motoneurons.