Rhythmic activity in the cerebellum and spinal cord of rabbits receiving tetanus toxin intravenously.

1. In rabbits intravenously injected with tetanus toxin (2 x 10(5) mouse LD50), a rhythmic electrical activity was recorded in the cerebellum and in the spinal cord. 2. The motor system appears to be strongly involved in this event, since the ventral roots displayed rhythmic activity correlated to the spinal cord rhythm. Extracellular recordings showed the same rhythmic discharge pattern in many alpha- and gamma-motoneurons and Renshaw cells of hindlimb flexor and extensor muscles. 3. Upon high spinalization at C1, the rhythm could be recorded in the cerebellum but no longer in the spinal cord. Cooling of the cerebellar surface suppressed the rhythm in both structures. 4. The data are discussed under the current view, that generalized tetanus is a special form of local tetanus. 5. We suggest that the rhythmic activity is of supraspinal origin and is transmitted to alpha- and gamma-motoneurons of both the flexor and extensor motor systems.