Fig. 4: Boosting CRH release in TRN promotes microarousals and decreases sigma power during NREMS.

a Schematic of the experimental approach for optogenetic activation of CRH release. EEG/EMG recordings were performed in ChannelRhodopsin2 (ChR2)-expressing CRH-IRES-Cre × Ai27D mice implanted with bilateral optic fibers positioned above the sensory TRN. CRH release was selectively photoactivated during NREMS using 456 nm light stimulation at 10 Hz, triggered every 50 s of closed-loop detected NREMS with a minimum interval of 50 s between stimulations. The depiction of LED train stimulation is illustrative. Representative images on the right demonstrate examples of optic fiber positioning (scale bars represent 500 µm) and expression of ChR2 in CRH-positive axons (CRH-ChR2—red). b Example of a polysomnographic recording with photoactivation of CRH release in the TRN during baseline and stimulation in the same mouse. The hypnograms at the top indicate the vigilance states and the occurrence of microarousals (MAs, marked by red dots), with the corresponding sigma power at the bottom. Blue-shaded areas indicate the timing of photostimulation. c Photoactivation of CRH release increased the number of MAs and decreased the average sigma power throughout NREMS (d) without change in delta power (e). f The surge in sigma power at transitions to REMS was also decreased by photoactivation of CRH release (g), which was accompanied by a prolonged latency to REMS from the peak of sigma (h). Data are represented as mean ± SEM, and n = 8. Statistical analysis was performed by a two-tailed paired t-test, with *p < 0.05, **p < 0.01, ***p < 0.001. For additional statistical information, see Supplementary Table 1. Source data are provided as a Source data file.