5-HT1A autoreceptor antagonist-induced 5-HT release in the hamster suprachiasmatic nuclei:: effects on circadian clock resetting

Serotonin (5-HT) has been implicated in phase shifting of mammalian circadian rhythms by non-photic stimuli. This study tests whether pharmacological induction of endogenous 5-HT release can shift circadian phase in the Syrian hamster, Systemic injections of the 5-HT1A antagonist WAY100635 during the mid-subjective day significantly increased 5-HT in dialysate from the hamster suprachiasmatic nucleus (SCN) circadian pacemaker by similar to 50% for 40-60 min. However, this was not associated with phase shifts or with potentiation of phase shifts induced by a 3 h bout of running. These results indicate that enhanced 5-HT release in the SCN or possibly other regions is not sufficient to induce phase shifts in the subjective day. (C) 2000 Elsevier Science Ireland Ltd. Ali rights reserved.