title: Vasopressin immunoreactivity and release in the suprachiasmatic nucleus of wild-type and tau mutant Syrian hamsters.
abstract: Despite the prominent role of the Syrian hamster (Mesocricetus auratus) in studies of circadian rhythms, there are no data available on the temporal dynamics of the neuropeptide vasopressin (AVP), a major output system of the suprachiasmatic nucleus (SCN). We studied the hamster SCN-AVP system in vivo across the light period and in vitro using long-term organotypic SCN cultures. Additionally, we compared wild-type and tau mutant hamsters with an endogenous circadian period of approximately 24 h and approximately 20 h, respectively. The in vivo study revealed no differences in the number of SCN-AVP neurons between the two genotypes of hamsters studied at three time points across the light period of the circadian cycle. A significantly higher level of AVP-immunoreactivity, however, was found in the SCN of wild-type compared to tau mutant hamsters at the beginning and in the middle of the light period, but not at the end of the light period. SCN-AVP cell number and immunostaining decreased significantly across the light period in wild-type hamsters, but not in tau mutants. The in vitro study revealed a significantly higher rate of AVP release per 24 h from the tau mutant SCN compared to the wild-type SCN. Robust circadian oscillations in AVP release were not found in either type of hamster. These results may suggest that the SCN-AVP system of hamsters, irrespective of genotype, is relatively weak compared to other species. Moreover, the tau mutation seems to influence the SCN-AVP system by enhancing the rate of AVP release and by reducing AVP content and its daily fluctuation.
authors: Zoological Laboratory, University of Groningen, P.O. Box 14, 9750 AA, Haren, The Netherlands. e.a.van.der.zee@biol.rug.nl
authors: Eddy A
authors: EA
authors: Van der Zee
authors: Malgorzata
authors: M
authors: Oklejewicz
authors: Koen
authors: K
authors: Jansen
authors: Serge
authors: S
authors: Daan
authors: Menno P
authors: MP
authors: Gerkema
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000235:genetics*; D047388:Casein Kinases; D002452:Cell Count; D002940:Circadian Rhythm / Q000235:genetics*; D006224:Cricetinae; D005838:Genotype; D007150:Immunohistochemistry; D008297:Male; D008647:Mesocricetus; D009154:Mutation / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009924:Organ Culture Techniques; D010775:Photic Stimulation; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism*; D014667:Vasopressins / Q000378:metabolism*
chemical_list: D014667:Vasopressins; D011494:Protein Kinases; D047388:Casein Kinases