The overall specific aims are to define the photoperiod conditions which permit expression of endogenous circannual rhythms of reproductive activity (anestrus versus estrous cycles as defined by blood progesterone) and prolactin secretion and to define the neural structures involved in generation and control of these rhythms using the sheep as the experimental model.
Specific aims are: 1. To complete a study in progress testing the hypothesis that endogenous rhythms of reproductive activity in sheep are expressed only under certain constant photoperiods. Expression of circannual rhythms of reproductive activity and prolactin secretion will be compared in ewes housed under 12L:12D versus 8L:16D photoperiods. 2. To test the hypothesis that the effect of a specific signal (photoperiod regimen) on expression of endogenous circannual rhythms depends on the stage of the annual rhythm at which that signal is applied. Ewes will be placed under 12L:12D at 4 distinct stages of their annual cycle. Subsequent patterns of reproductive activity and prolactin secretion will be monitored. 3. To test the hypothesis that expression of an endogenous rhythm of reproductive activity is masked in ovary-intact ewes kept under a 12L:12D photoperiod. Comparison will be made of temporal changes in onset and cessation of estrous cycles in intact ewes versus changes of LH in ovariectomized estrogen-treated ewes housed under 12L:12D and 8L:16D photoperiods. 4. To test the null hypothesis that removal of the olfactory bulbs will not affect the ability of photoperiod changes to alter LH and prolactin secretion in ewes. The effect of olfactory bulbectomy on basal secretion of LH and FSH and on responses of these hormones to changes in photoperiod will be monitored. 5. To test the null hypotheses that lesions of the suprachiasmatic nucleus (SCN), lesions of the anterior hypothalamic area (AHA), or olfactory bulbectomy will not affect expression of circannual rhythms of reproductive activity and prolactin secretion in ewes kept under a constant photoperiod. In 3 separate experiments ewes will be subjected to either SCN lesions, AHA lesions, olfactory bulbectomy, or sham surgery and then housed under 8L:16D to determine if expression of the putative endogenous rhythm is altered.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD013037-15
Application #
3312069
Study Section
Reproductive Biology Study Section (REB)
Project Start
1979-08-01
Project End
1995-03-31
Budget Start
1993-04-01
Budget End
1994-03-31
Support Year
15
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Illinois Urbana-Champaign
Department
Type
Schools of Veterinary Medicine
DUNS #
041544081
City
Champaign
State
IL
Country
United States
Zip Code
61820
Jansen, H T; Iwamoto, G A; Jackson, G L (1998) Central connections of the ovine olfactory bulb formation identified using wheat germ agglutinin-conjugated horseradish peroxidase. Brain Res Bull 45:27-39
Jansen, H T; Hileman, S M; Lubbers, L S et al. (1997) Identification and distribution of neuroendocrine gonadotropin-releasing hormone neurons in the ewe. Biol Reprod 56:655-62
Jansen, H T; Hileman, S M; Lubbers, L S et al. (1996) A subset of estrogen receptor-containing neurons project to the median eminence in the ewe. J Neuroendocrinol 8:921-7
Scott, C J; Jansen, H T; Kao, C C et al. (1995) Disruption of reproductive rhythms and patterns of melatonin and prolactin secretion following bilateral lesions of the suprachiasmatic nuclei in the ewe. J Neuroendocrinol 7:429-43
Hileman, S M; Kuehl, D E; Jackson, G L (1994) Effect of anterior hypothalamic area lesions on photoperiod-induced shifts in reproductive activity of the ewe. Endocrinology 135:1816-23
Jansen, H T; Jackson, G L (1993) Olfactory bulb removal does not prevent gonadotropin or prolactin responses to changing photoperiod in the ewe. Neuroendocrinology 57:448-56
Lubbers, L S; Jackson, G L (1993) Neuroendocrine mechanisms that control seasonal changes of luteinizing hormone secretion in sheep are sexually differentiated. Biol Reprod 49:1369-76
Jansen, H T; Jackson, G L (1993) Circannual rhythms in the ewe: patterns of ovarian cycles and prolactin secretion under two different constant photoperiods. Biol Reprod 49:627-34
Marcinkiewicz, J L; Moy, E S; Bahr, J M (1992) Change in responsiveness of rabbit corpus luteum to prostaglandin F-2 alpha during pregnancy and pseudopregnancy. J Reprod Fertil 94:305-10
Jackson, G L; Kuehl, D; Rhim, T J (1991) Testosterone inhibits gonadotropin-releasing hormone pulse frequency in the male sheep. Biol Reprod 45:188-94

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