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bioRxiv · 10.1101/2024.07.09.602643

Ultraslow serotonin oscillations in the hippocampus delineate substates across NREM and waking

Cooper, C.·Parthier, D.·Sibille, J.·Tukker, J. J.·Tritsch, N. X.·Schmitz, D.
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Abstract

Beyond the vast array of functional roles attributed to serotonin (5-HT) in the brain, changes in 5-HT levels have been shown to accompany changes in behavioral states, including WAKE, NREM and REM sleep. Whether 5-HT dynamics at shorter time scales can be seen to delineate substates within these larger brain states remains an open question. Here, we performed simultaneous recordings of extracellular 5-HT using a recently-developed G Protein-Coupled Receptor-Activation-Based 5-HT sensor (GRAB5-HT3.0) and local field potential (LFP) in the hippocampal CA1, which revealed the presence of prominent ultraslow (<0.05 Hz.) 5-HT oscillations both during NREM and WAKE states. Interestingly, the phase of these ultraslow 5-HT oscillations was found to distinguish substates both within and across larger behavioral states. Hippocampal ripples occurred preferentially on the falling phase of ultraslow 5-HT oscillations during both NREM and WAKE, with higher power ripples concentrating near the peak specifically during NREM. By contrast, hippocampal-cortical coherence was strongest and microarousals and intracranial EMG peaks were most prevalent during the rising phase in both wake and NREM. Overall, ultraslow 5-HT oscillations delineate substates within the larger behavioral states of NREM and WAKE, thus potentially temporally segregating internal memory consolidation processes from arousal-related functions.

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Cooper, C., Parthier, D., Sibille, J., Tukker, J. J., Tritsch, N. X., Schmitz, D.. 2024-07-13. Ultraslow serotonin oscillations in the hippocampus delineate substates across NREM and waking. https://doi.org/10.1101/2024.07.09.602643

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