Two distinct serotonin receptors co-mediate non-photic signals to the circadian clock

Several lines of evidence indicate that serotonin type 7 (5-ht7) receptors play a critical role for non-photic resetting of the mammalian circadian clock; however,the contributions of other types of 5-ht receptors to non-photic entrainment are not yet clarified. the present study demonstrates that mkc-242,a selective 5-ht1a receptor agonist,can evoke a non-photic-like phase-response in hamsters in vivo. this phase-shifting response to mkc-242 was antagonized not only by the selective 5-ht1a receptor blocker way100635 but also by the selective 5-ht7 receptor blocker dr4004. these suggest that synchronous activation of 5-ht1a and 5-ht7 receptors mediates non-photic signals to the hamster circadian clock. © the japanese pharmacological society.