Increase of multiple unit activity during slow wave sleep in the cat preoptic area

Multiple unit activities (MUA) in 307 brainstem sites were recorded by chronically implanted electrodes in cats, using a polygraph with 4 channel MUA recording units. During transition from waking to slow wave sleep, at 15 sites including the medial preoptic area (11), the diagonal band of Broca (2) and medial anterior hypothalamic area (2), consistently earlier increase of MUA in discharge rate was observed, while MUA in other areas decreased. Also, at 13 sites in these areas, a decrease in discharge rate was demonstrated during paradoxical sleep. These findings suggest a close relationship between the preoptic area and sleep mechanisms, supporting a notion that an active site for induction of slow wave sleep may reside in the preoptic area.