Spinally projecting neurones near the ventral surface of the medulla in the cat

In anaesthetized cats antidromic responses were recorded in nucleus paragigantocellularis lateralis following stimulation of the ventrolateral funiculus in the ipsilateral thoracolumbar cord. Conduction velocities ranged from 5.4-120 m/s but 50% of the fibres conducted at less than 20 m/s. About half of the neurones were facilitated by stimulation in the hypothalamic or midbrain defence areas. These neurones are superficially located at the site where application of glycine or a lesion blocks the effects of defence area stimulation and reduces blood pressure. They could therefore be involved in the regulation of vasomotor activity.