Assistant Professor  Department of VCAPP College of Veterinary Medicine Washington State University Pullman, WA 99164-6520 Phone: 509-335-7056 FAX: 509-335-4650 E-mail: heiko@ vetmed.wsu.edu   Ph.D., 1993 University of Illinois at Urbana/Champaign RESEARCH INTERESTS:  Neuroendocrine Control of Reproduction RESEARCH SUMMARY: Research centers on investigations of the neural mechanisms controlling reproduction in seasonally breeding mammals. A complex and poorly understood interaction between environmental and endogenous signals (e.g. changes in daylength, steroid hormones) modulates the activity of a subset of neurons secreting the decapeptide, gonadotropin releasing-hormone (GnRH), to ultimately affect gamete production in both males and females. GnRH neurons and their projections to the median eminence represent the final common pathway in the neural control of reproduction for all vertebrates. To ensure that young are born at favorable times, temperate zone species have adapted a highly successful strategy of restricting reproductive activity to limited portions of the sidereal year. Changes in daylength (photoperiod) serve as the predominant factor responsible for causing reproductive transitions ('Nature's contraceptive') in many of these species. Yet, how the photoperiod signal is conveyed to the GnRH neurons remains a key unanswered question in the field. The bulk of evidence suggests that photoperiodic information (via the endocrine signal for daylength - melatonin) reaches GnRH neurons indirectly through neural inputs from other brain regions. Some of these neurons likely bind the ovarian steroid, estradiol, whose influence on the neuroendocrine axis varies with season and is considered a key processes responsible for causing seasonal reproductive variation. Because GnRH neurons themselves contain little, if any, gonadal steroid receptors a major thrust of the work involves identify estrogen-responsive neural systems that convey information indirectly to GnRH neurons. Using the sheep as a model, our goal is to advance a more unified hypothesis of the mechanisms underlying the seasonal control of reproduction by using neuroanatomical, molecular, and systems approaches.   REPRESENTATIVE PUBLICATIONS: Jansen HT and Jackson GL: (1993). Circannual rhythms in the ewe: Pattern of ovarian cycles and prolactin secretion under two different constant photoperiods. Biology of Reproduction 49:627-634. Scott CJ, Jansen HT, Kao C-C, Kuehl DE, and Jackson GL: (1995) Disruption of reproductive rhythms and patterns of melatonin and prolactin secretion following bilateral lesions of the suprachiasmatic nuclei in the ewe. Journal of Neuroendocrinology 7:429-443 Lehman MN, Durham DM, Jansen HT, Adrian B, Goodman RL: (1996) Dopaminergic A14/A15 neurons are activated during estradiol negative feedback in anestrous, but not breeding season, ewes. Endocrinology 137:443-450. Jansen HT, Hileman SM, Lubbers LS, Jackson GL, and Lehman MN: (1996) A subset of estrogen receptor-containing neurons project to the median eminence in the ewe. Journal of Neuroendocrinology 8:921-927. Jansen HT, Hileman SM, Lubbers LS, Kuehl DE, Jackson GL, and Lehman MN: (1997) Identification and distribution of neuroendocrine GnRH neurons in the ewe. Biology of Reproduction 56:655-662. Jansen HT, Iwamoto GA, and Jackson GL: (1997) Central connections of the ovine olfactory bulb formation identified using wheatgerm agglutinin-conjugated horseradish peroxidase. Brain Research Bulletin 45(1):27-39. Jansen HT, Lubbers LS, Macchia E, DeGroot LJ, and Lehman MN: (1997) Thyroid hormone receptor (a) distribution in hamster and sheep brain: colocalization in gonadotropin-releasing hormone and other identified neurons. Endocrinology 138:5039-5047. Coolen LM, Jansen HT, Goodman RL, Wood RI, Lehman MN: (1999) A method for simultaneous demonstration of anterograde and retrograde connections in the brain: Co-injections of biotinylated dextran amine and the beta subunit of cholera toxin. Journal of Neuroscience Methods 15:1-8. Stefanovic I, Adrian B, Jansen HT, Lehman MN, Goodman RL: (2000) The ability of estradiol to induce fos expression in a subset of estrogen receptor a-containing neurons in the ewe is dependent upon reproductive status. Endocrinology 141:190-196. Viguie C, Jansen HT, Glass JD, Watanabe M, Billings HJ, Coolen L, Lehman MN, Karsch FJ. ·2001) Potential for polysialylated form of neural cell adhesion molecule-mediated neuroplasticity within the gonadotropin-releasing hormone neurosecretory system of the ewe. Endocrinology. 142(3):1317-24. Jansen HT, West C, Lehman MN, Padmanabhan V. 2001. Ovarian estrogen receptor-beta (ERbeta) regulation: I. Changes in ERbeta messenger RNA expression prior to ovulation in the ewe.Biol Reprod. 65(3):866-72. Sleipness EP, Sorg BA, Jansen HT. 2005 Time of day alters long-term sensitization to cocaine in rats. Brain Res. 1065(1-2):132-7. Jansen HT, Cutter C, Hardy S, Lehman MN, Goodman RL. 2003 Seasonal Plasticity within the Gonadotropin-Releasing Hormone (GnRH) System of the Ewe: Changes in Identified GnRH Inputs and Glial Association. Endocrinology. 144(8):3663-76. Romeo RD, Wagner CK, Jansen HT, Diedrich SL, Sisk CL. 2002 Estradiol induces hypothalamic progesterone receptors but does not activate mating behavior in male hamsters (Mesocricetus auratus) before puberty. Behav Neurosci.116(2):198-205.