Urea-induced stimulus-sensitive myoclonus in the rat.

Uremia in humans can cause spontaneous and stimulus-sensitive myoclonus that responds to clonazepam. Uremic myoclonus in humans resembles the reticular reflex form of postanoxic action myoclonus. Previous investigations have established that urea infusions in the cat can produce spontaneous and stimulus-sensitive myoclonus. This has been shown, electrophysiologically, to arise in the brainstem medullary reticular formation, and it does not require forebrain structures. Our own studies in the rat have shown that urea infusions also produce spontaneous and stimulus-sensitive myoclonus. Electrophysiologically, this resembles human reticular reflex myoclonus. It can be reduced by clonazepam. The myoclonus produced by urea infusions in the rat progresses very rapidly into uncontrollable tonic-clonic convulsions. Although the urea model in the rat mimics some forms of human myoclonus that arise in the brainstem, it is not suitable as a routine animal model for pharmacological investigations.