Slow intrinsic oscillations in the ventrolateral preoptic nucleus

The ventrolateral preoptic nucleus (VLPO) promotes non-rapid eye movement (NREM) sleep. While VLPO neurons often display low-threshold spikes (LTSs), a feature that supports rhythmic activity, rhythmic bursting has never been reported in these neurons. Here, we report that ∼12% of VLPO neurons in a large ex vivo patch-clamp dataset exhibit spontaneous rhythmic bursting. This pattern occurred in putative sleep-promoting neurons (inhibited by noradrenaline, NA), and in wake-active neurons (excited by NA). Unsupervised clustering of 24 bursting neurons using burst parameters, electrophysiological, and morphological features revealed three groups: one putative sleep-promoting subtype and two wake-active subtypes with fast and slow bursting. Strikingly, membrane potential oscillations persisted in tetrodotoxin (TTX), indicating an intrinsic mechanism. Bursts of inhibitory inputs were also recorded on sleep-promoting neurons. These results suggest that intrinsic rhythmic bursting may propagate to the local network, with functional relevance for sleep regulation.