Electroencephalographic synchronization induced by stimulation of small intestine and splanchnic nerve in cats.

1. In freely moving cats, the cortical desynchronization elicited by painless rhythmic distension, or by low voltage electric stimulation, of the small intestine in drowsiness and slow wave sleep is extinguished following a few repetitions. After extinction of the arousal reaction, similar intestinal stimulation was systematically followed by the appearance of synchronized activity, or an increase of spontaneous synchronization, in the explored cortical areas (parieto-occipital). 2. Intestinal or splanchnic stimulation at an intensity below threshold for cortical desynchronization immediately induced synchronized activity without any need of previous repetitions of stimulation. 3. Stimuli which were followed by synchronization excited only the large (Abeta) splanchnic afferents. The authors conclude that intestinal receptors may be one of the sources of synchronizing influence which can contribute to the regulation of the sleep-wakefulness cycle and that the large splanchnic afferents may play a role in the induction of synchronization.