title: Seasonal regulation of reproduction: altered role of melatonin under naturalistic conditions in hamsters.
abstract: The seasonal reproductive cycle of photoperiodic rodents is conceptualized as a series of discrete melatonin-dependent neuroendocrine transitions. Least understood is the springtime restoration of responsiveness to winter-like melatonin signals (breaking of refractoriness) that enables animals to once again respond appropriately to winter photoperiods the following year. This has been posited to require many weeks of long days based on studies employing static photoperiods instead of the annual pattern of continually changing photoperiods under which these mechanisms evolved. Maintaining Siberian hamsters under simulated natural photoperiods, we demonstrate that winter refractoriness is broken within six weeks after the spring equinox. We then test whether a history of natural photoperiod exposure can eliminate the requirement for long-day melatonin signalling. Hamsters pinealectomized at the spring equinox and challenged 10 weeks later with winter melatonin infusions exhibited gonadal regression, indicating that refractoriness was broken. A photostimulatory effect on body weight is first observed in the last four weeks of winter. Thus, the seasonal transition to the summer photosensitive phenotype is triggered prior to the equinox without exposure to long days and is thereafter melatonin-independent. Distinctions between photoperiodic and circannual seasonal organization erode with the incorporation in the laboratory of ecologically relevant day length conditions.
authors.affiliation: Department of Integrative Biology and, University of California, , Berkeley, CA 94720, USA. mb3024@columbia.edu
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Butler
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Turner
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Park
authors.forename: Elanor E
authors.initials: EE
authors.lastname: Schoomer
authors.forename: Irving
authors.initials: I
authors.lastname: Zucker
authors.forename: Michael R
authors.initials: MR
authors.lastname: Gorman
mesh_terms: D000818:Animals; D001835:Body Weight; D006224:Cricetinae; D006066:Gonads / Q000502:physiology; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D017111:Phodopus / Q000502:physiology*; D017440:Photoperiod; D010870:Pineal Gland / Q000601:surgery; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D015398:Signal Transduction; D013737:Testis / Q000502:physiology
chemical_list: D008550:Melatonin
references.citation: Endocrinology. 1984 Feb;114(2):664-70
references.pmid: 6418534
references.citation: J Biol Rhythms. 2006 Oct;21(5):373-83
references.pmid: 16998157
references.citation: Q Rev Biol. 2001 Sep;76(3):293-325
references.pmid: 11561508
references.citation: Curr Biol. 2008 Aug 5;18(15):1147-52
references.pmid: 18674911
references.citation: Endocrinology. 2008 Nov;149(11):5527-39
references.pmid: 18669596
references.citation: J Neuroendocrinol. 2003 Feb;15(2):191-6
references.pmid: 12535161
references.citation: Proc Natl Acad Sci U S A. 2001 May 22;98(11):6447-52
references.pmid: 11353850
references.citation: Am J Physiol Regul Integr Comp Physiol. 2001 Nov;281(5):R1613-23
references.pmid: 11641134
references.citation: Endocrinology. 1985 Jan;116(1):424-30
references.pmid: 3917252
references.citation: Curr Biol. 2005 Jun 21;15(12):R449-50
references.pmid: 15964261
references.citation: J Biol Rhythms. 2001 Aug;16(4):283-301
references.pmid: 11506375
references.citation: J Biol Rhythms. 1991 Winter;6(4):315-30
references.pmid: 1773098
references.citation: Biol Reprod. 1994 Nov;51(5):1046-50
references.pmid: 7849181
references.citation: J Neuroendocrinol. 2007 Feb;19(2):102-8
references.pmid: 17214872
references.citation: Endocrinology. 2005 Sep;146(9):3782-90
references.pmid: 15919753
references.citation: Brain Res. 1992 Dec 11;598(1-2):98-106
references.pmid: 1486507
references.citation: Biol Reprod. 1981 Apr;24(3):568-72
references.pmid: 7236821
references.citation: Endocrinology. 1983 Oct;113(4):1261-7
references.pmid: 6617572
references.citation: Biol Reprod. 1986 May;34(4):664-9
references.pmid: 3708050
references.citation: J Pineal Res. 1987;4(1):79-88
references.pmid: 3470503
references.citation: J Exp Zool A Ecol Genet Physiol. 2009 Aug 1;311(7):475-82
references.pmid: 19425044
references.citation: J Biol Rhythms. 2008 Jun;23(3):242-51
references.pmid: 18487416
references.citation: Biol Reprod. 2000 Sep;63(3):769-74
references.pmid: 10952919
references.citation: J Biol Rhythms. 2008 Dec;23(6):502-10
references.pmid: 19060259
references.citation: Am J Physiol. 1996 Oct;271(4 Pt 2):R1041-6
references.pmid: 8897998
references.citation: Endocrinology. 2004 Apr;145(4):1546-9
references.pmid: 14726436
references.citation: Chronobiol Int. 2006;23(1-2):301-6
references.pmid: 16687303
references.citation: J Neuroendocrinol. 2003 Nov;15(11):1084-94
references.pmid: 14622439
references.citation: J Comp Physiol A. 1994 Apr;174(4):469-84
references.pmid: 8182563
references.citation: J Biol Rhythms. 2000 Apr;15(2):122-5
references.pmid: 10762030
references.citation: Biol Reprod. 1995 Jul;53(1):110-5
references.pmid: 7669841
references.citation: J Biol Rhythms. 2000 Oct;15(5):417-28
references.pmid: 11039919
references.citation: Gen Comp Endocrinol. 1969 Jun;12(3):460-8
references.pmid: 5769935
references.citation: Am J Physiol. 1991 Sep;261(3 Pt 2):R670-6
references.pmid: 1887954
references.citation: Philos Trans R Soc Lond B Biol Sci. 2008 Jan 27;363(1490):341-61
references.pmid: 17686736
references.citation: J Biol Rhythms. 1999 Feb;14(1):62-71
references.pmid: 10036994
references.citation: J Exp Zool. 1977 Oct;202(1):81-8
references.pmid: 925665
references.citation: Fed Proc. 1976 Oct;35(12):2339-46
references.pmid: 964387
references.citation: Biol Reprod. 1995 Jul;53(1):116-25
references.pmid: 7669842
references.citation: Curr Biol. 2008 Sep 9;18(17):R795-R804
references.pmid: 18786385
references.citation: J Endocrinol. 2003 Oct;179(1):1-13
references.pmid: 14529560
references.citation: Am J Physiol Regul Integr Comp Physiol. 2007 Jul;293(1):R413-20
references.pmid: 17491109
references.citation: Endocrinology. 1991 Mar;128(3):1337-44
references.pmid: 1999155
references.citation: J Comp Physiol A. 1986 Jul;159(1):7-11
references.pmid: 3746726
references.citation: Endocrinology. 1995 Jan;136(1):144-53
references.pmid: 7828525
references.citation: Am J Physiol. 1997 Mar;272(3 Pt 2):R887-95
references.pmid: 9087652
references.citation: Proc Natl Acad Sci U S A. 2002 Dec 10;99(25):16291-6
references.pmid: 12456888
references.citation: Am J Physiol Regul Integr Comp Physiol. 2007 Jul;293(1):R402-12
references.pmid: 17428890