The proposed research evaluates the impact of several physiological stimuli on circannual rhythms of golden-mantled ground squirrels, including the role of endogenous circannual fluctuations in body temperature on circannual variations in circadian organization and metabolic rate. The decrease in body temperature normally associated with the hibernation season will be blocked and the presence of circannual variations in circadian entrainment and metabolic rate determined. The role of prenatal photoperiod in the timing/generation of circannual rhythms of young squirrels will also be examined in squirrels kept either in constant light, to eliminate photoperiod cues, or a simulated natural photoperiod during gestation. The timing and/or presence of circannual rhythms in the offspring of these females will be examined. Neural sites at which testosterone (T) suppresses hibernation will be examined in male squirrels implanted with cannulae containing T into neural sites that contain T receptors and implicated in thermoregulation. The inhibitory role of the suprachiasmatic nucleus (SCN) in circannual timing of hibernation and reproduction in male squirrels will be examined to determine if this nucleus functions similarly in males as in females to limit hibernation and reproduction to particular times of year. This research may help in the development of interventions for treating human disorders that have a circannual basis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
5F32MH011655-02
Application #
2796912
Study Section
Psychobiology, Behavior, and Neuroscience Review Committee (PBN)
Program Officer
Goldschmidts, Walter L
Project Start
1998-10-01
Project End
Budget Start
1998-10-01
Budget End
1999-09-29
Support Year
2
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of California Berkeley
Department
Psychology
Type
Schools of Arts and Sciences
DUNS #
094878337
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Freeman, D A; Larkin, J E; Seliby, L (2002) Testicular and somatic growth in Siberian hamsters depend on the melatonin-free interval between twice daily melatonin signals. J Neuroendocrinol 14:228-33
Freeman, David A; Herron, Jana M; Duncan, Marilyn J (2002) Absence of pineal-independent mediation of seasonal differences in suprachiasmatic nucleus AVP and VIP mRNA expression in Siberian hamsters. Brain Res Mol Brain Res 101:33-8
Lewis, D; Freeman, D A; Dark, J et al. (2002) Photoperiodic control of oestrous cycles in Syrian hamsters: mediation by the mediobasal hypothalamus. J Neuroendocrinol 14:294-9
Prendergast, Brian J; Freeman, David A; Zucker, Irving et al. (2002) Periodic arousal from hibernation is necessary for initiation of immune responses in ground squirrels. Am J Physiol Regul Integr Comp Physiol 282:R1054-62
Larkin, J E; Freeman, D A; Zucker, I (2001) Low ambient temperature accelerates short-day responses in Siberian hamsters by altering responsiveness to melatonin. J Biol Rhythms 16:76-86
Freeman, D A; Zucker, I (2001) Refractoriness to melatonin occurs independently at multiple brain sites in Siberian hamsters. Proc Natl Acad Sci U S A 98:6447-52
Freeman, D A; Zucker, I (2000) Temperature-independence of circannual variations in circadian rhythms of golden-mantled ground squirrels. J Biol Rhythms 15:336-43