In Syrian hamsters, 5-HT fibres within the suprachiasmatic nuclei are necessary for the expression of 8-OH-DPAT induced phase-advance of locomotor activity rhythm.
8-Hydroxy-2-[di-n-propylamino]-tetralin) (8-OH-DPAT), a 5-HT1A/7 receptor agonist, has a chronobiological effect on the circadian system. To identify how the 8-OH-DPAT exerts this effect, we specifically destroyed the serotonergic (5-HT) fibres connecting the median raphe nuclei (RN) to the suprachiasmatic nuclei (SCN) of the hypothalamus by using microinjections of a neurotoxin 5,7-dihydroxytryptamine into the SCN. After administration of 8-OH-DPAT (0.1 ml, 5 mg/kg) at circadian time 7, the control and the 'partially-lesioned' animals showed a large phase-advance whereas in the 'well-lesioned' hamsters the phase-advances were significantly reduced or absent. The present study demonstrates that, in the Syrian hamster, the 5-HT fibres connecting the RN to the SCN are essential for the phase-shifting action of peripheral 8-OH-DPAT injections, and that the drug does very probably not exert its chronobiological effect directly onto SCN neurons but through receptors localized on median raphe nucleus neurons.
Schuhler
S
S
CNRS-UMR 7518, Laboratoire de Neurobiologie des Fonctions Rythmiques et Saisonnières, Université Louis Pasteur, Strasbourg, France. schuhler@neurochem.u-strasbg.fr
Saboureau
M
M
Pitrosky
B
B
Pévet
P
P
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D006224:Cricetinae; D008297:Male; D008647:Mesocricetus; D009043:Motor Activity / Q000187:drug effects*; D009412:Nerve Fibers / Q000502:physiology*; D011903:Raphe Nuclei / Q000502:physiology; D012701:Serotonin / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013493:Suprachiasmatic Nucleus / Q000502:physiology*
D017366:Serotonin Receptor Agonists; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin