Phase-resetting effect of 8-OH-DPAT, a serotonin1A receptor agonist, on the circadian rhythm of firing rate in the rat suprachiasmatic nuclei in vitro.
The 5-HTergic neurons in the mesencephalic raphe nuclei provide a robust projection to the hypothalamic suprachiasmatic nucleus (SCN), the site of a putative neuronal circadian pacemaker. Although it has been suggested that 5-HT neurons may play a role in the circadian timing system, this role has not yet been specified. Prosser et al. (Brain Res., 534 (1990) 336-339) reported that 1 h treatments with quipazine induce robust phase shifts in vitro, and that this effect depends upon the circadian time of treatment. However, quipazine is a non-specific 5-HT agonist. Besides, it is reported that the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino)tetraline hydrobromide (8-OH-DPAT) affected a circadian rhythm of hamster wheel-running activity. In the present study we investigated whether the 5-HT1A agonist 8-OH-DPAT can reset the phase of the SCN clock when it is isolated in vitro. The present results show that 1 h treatments with 8-OH-DPAT induce robust phase advances in vitro when it was administered during the subjective day. This result suggests that 5HT1A receptor functioning may play a role in modulating the phase of SCN clock, especially during the subjective day.
Shibata
S
S
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Tsuneyoshi
A
A
Hamada
T
T
Tominaga
K
K
Watanabe
S
S
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects*; D002940:Circadian Rhythm / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects*
D011985:Receptors, Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin