Monoamine changes in the brain of cats during slow-wave sleep.

We have found that the metabolism of 5-hydroxytryptamine increases in the hippocampus and that the metabolism of dopamine decreases in the striatum and thalamus during slow-wave sleep, and we suggest that these changes are related to this stage of sleep. We have also found that the concentration of dopamine increases in the hippocampus during slow-wave sleep, and suggest that this may be related to the subsequent appearance of paradoxical sleep. These data raise new questions on the hippocampal role in the sleep-wakefulness cycle.