ELECTRICAL STIMULATION OF THE NEURAL MECHANISM REGULATING SPASMODIC RESPIRATORY ACTS IN THE CAT

Abstract

The interior of the medulla oblongata of the cat has been stimulated with the aid of the Horsley-Clarke stereotaxic instrument and a rhythmic spasmodic respiratory response as typically seen in coughing, sneezing and retching has been obtained. Recordings of the respiration were made with thoracic and abdominal pneumographs which were adapted from blood pressure cuffs (8 cm.); the specific character of the response was recognizable because the glottis was left undisturbed. The voltage and frequency ranges of the stimulating current in which the response was elicitable were, respectively, 6-19 volts and 7-25 impulses per sec. By histological identification of the reactive points of 40 cats, the responsive region for the spasmodic response was localized to an area corresponding to the descending vestibular tract and nucleus, the tractus solitarius and its nucleus and the entering 9th and 10th cranial nerve rootlets, extending from the level of the 6th cranial nerve caudad to the level of the 12th cranial nerve. The topography of the spasmodic respiratory center and the repetitive character of the response suggest that it may be related to the mechanism of pneumotaxis.