Comparative distribution of the hypothalamic neurons activated during wakefulness and paradoxical (REM) sleep using male TRAP2-red mice: contribution of orexin, MCH, Lhx6, and a new marker Meis2

Our study identifies new neuronal populations activated during PSR in AHA, ZI, and tuberal nucleus. We further provide evidence that Meis2 is expressed in novel populations of neurons activated during PSR. In summary, our results using male TRAP2-red mice characterize the cell populations activated during wakefulness and PSR, opening experimental paths for determining their function regarding vigilance states. Statement of Significance Wakefulness and paradoxical sleep are very similar at the electroencephalographic level. It remains relevant to determine the potential overlap of the neurons active during each vigilance state. We here took advantage of the powerful transgenic male TRAP2-red mice to directly compare in the same animal the brain cell activation during both states, with a focus on the hypothalamus. A deeper knowledge of each individual subpopulation of hypothalamic neurons within complex brain circuits underlying the sleep-waking cycle will help the understanding and validation of treatments of sleep disorders, at least those directly linked to demonstrated hypothalamic dysfunction such as narcolepsy (Orx neurons), amyotrophic lateral sclerosis (MCH and Orx signaling) or neurodegenerative diseases (Parkinson's and Alzheimer diseases).