Enhancing endogenous adenosine A_2A receptor signaling induces slow-wave sleep without affecting body temperature and...

Insomnia is one of the most common sleep problems with an estimated prevalence of 10%-15% in the general population. Although adenosine A_2A receptor (A_2AR) agonists strongly induce sleep, their cardiovascular effects preclude their use in treating sleep disorders. Enhancing endogenous A_2AR signaling, however, may be an alternative strategy for treating insomnia, because adenosine levels in the brain accumulate during wakefulness. In the present study, we found that 3,4-difluoro-2-((2-fluoro-4-iodophenyl)amino)benzoic acid, denoted A_2AR positive allosteric modulator (PAM)-1, enhanced adenosine signaling at the A_2AR and induced slow wave sleep (SWS) without affecting body temperature in wild-type male mice after intraperitoneal administration, whereas the SWS-inducing effect of this benzoic acid derivative was abolished in A_2AR KO mice. In contrast to the A_2AR agonist CGS 21680, the A_2AR PAM-1 did not affect blood pressure or heart rate. These findings indicate that enhancing A_2AR signaling promotes SWS without cardiovascular effects. Therefore, small molecules that allosterically modulate A_2ARs could help people with insomnia to fall asleep.