A critical reticular site involved in the spino-bulbo-spinal reflex system.

1. In precollicular decerebrate cats, the nucleus reticularis gigantocellularis in the medullar was identified to be critically involved in the spino-bulbo-spinal (SBS) reflex system. 2. Electrolytic lesion place in this nucleus eliminated the SBS reflex and its associated effects in the spinal cord. 3. Ascending volleys from the spinal cord were found to excite neurons within this nucleus, whereupon further direct stimulation was able to enhance the inhibitory effects of the SBS reflex on spinal motoneurons. These interactions were also facilitated by physostigmine and suppressed by atropine, indicating the cholinoceptive nature of these neurons, another criterion which qualified them as being associated with the SBS reflex. 4. The functional roles of SBS reflex and nucleus reticularis gigantocellularis in somatic and visceral activities were discussed.