Trigemino-Bulbar Reflex Pathways

Abstract

In decerebrate and decerebellate cats stimulation of any division of the trigeminal nerve induces efferent volleys in the VIIth, Xth, XIth and XIIth nerves. Direct stimulation of the face, internal nares and dura mater produces similar volleys. In uncurarized animals similar stimuli cause twitches of face and neck muscles. Slowing of the heart rate may also be induced. Conduction times measured in the brainstem and cranial nerves show that conduction is very rapid in the brainstem to the level of the obex, so that large medullated fibers may be inferred. At the level of the obex a delay of 2–4 msec. occurs, presumably due to synapses and internuncial neurones. Conduction of the volleys in the Xth and XIth nerves is rapid and large fibers must be involved. Removal of the dorsal vagal nuclei does not abolish the vagal reflex which is presumed to relay at the nucleus ambiguus. The vagal responses are very easily fatigued.