Suprasegmental inhibition and facilitation after injection of tetanus toxin into the medullary nuclei (the so-called dispatch station phenomenon)

Abstract

Changes in descending inhibition and facilitation evoked by stimulation of the nucleus fastigii were studied after injection of tetanus toxin into the relay nuclei of the medulla in experiments on cats under superficial pentobarbital-chloralose anesthesia. Injection of tetanus toxin into these nuclei leads to an increase in their “functional dispatch.” Descending inhibition (in response to injection of tetanus toxin into the gigantocellular nucleus) and descending facilitation (injection of the toxin into Deiters' nucleus and the nucleus ambiguus) were increased to many times their previous intensity, the latent periods of the descending effects were considerably shortened, their intensity rose sharply to a maximum, and their duration was greatly lengthened. To interpret these results it is postulated that powerful excitation generators are formed in the relay nuclei following disturbance of their inhibitory mechanisms. These results indicate that the “dispatch station” concept is applicable also to supraspinal structures.