Altered expression of adenosine A1 receptor in the paraventricular thalamus and its role in the regulation of sleep

Objective‍ ‍To explore the expression profile of adenosine A1 receptor in the paraventricular thalamic nucleus (PVT) in wakefulness/sleep state and its role in regulating sleep. Methods‍ ‍Male C57BL/6J mice (6~12 weeks old, weighing 22~28 g) were randomly divided into ZT0, ZT6, ZT10, ZT12, and sleep deprivation and recover0y sleep groups (n=16 or n=4). RT-qPCR and fluorescence in situ hybridization were used to observe the changes of adenosine A1 receptor in PVT. Whole-cell patch-clamp recording was conducted to determine the effects of adenosine on the membrane potential and discharge frequency of PVT neurons. The experimental animals were divided into adenosine A1 receptor interference group (n=8) and interference control group (n=7). After RNA interference, electroencephalography (EEG) and electromyography (EMG) were applied simultaneously to observe the changes in wake and sleep time between the 2 groups during sleep deprivation for 6 h and sleep recovery for 4 h. Results‍ ‍RT-qPCR and fluorescence in situ hybridization confirmed that the expression of adenosine A1 receptor in PVT was affected by wakefulness/sleep state, with the level in the ZT0 group (active stage) significantly higher than that in the ZT12 group (non-active stage, P<0.05). Whole-cell patch clamp recording indicated that adenosine exerted inhibitory effects on PVT neurons through 2 distinct response types (P<0.05), and the inhibition was in a diminishing trend with a decrease in the expression level of adenosine A1 receptor. After sleep deprivation, the expression level of adenosine A1 receptor showed significant intergroup differences: the level was significantly higher in the sleep deprivation group than the recovery sleep group (P<0.05), while that of the recovery sleep group was higher than that of the ZT6 group and that of the ZT10 group (P<0.05). After knocking down adenosine A1 receptor (shRNA-A1R) in the PVT, the wakefulness timing of the shRNA-A1R group was significantly increased, while the sleep timing was significantly decreased within 1 h after sleep recovery when compared with the interference control group (P<0.05). Conclusion‍ ‍The expression of adenosine A1 receptor in the PVT is dynamically regulated by sleep pressure, which was increasing as sleep pressure rises.