title: Simultaneous observation of the GnRH pulse generator activity and plasma concentrations of metabolites and insulin during fasting and subsequent refeeding periods in Shiba goats.
abstract: The time course of GnRH pulse generator activity and plasma concentrations of energy substrates and insulin were simultaneously observed in female goats during 4-day fasting and subsequent refeeding in the presence or absence of estrogen for a better understanding of the mechanism of energetic control of gonadotropin secretion in ruminants. The GnRH pulse generator activity was electrophysiologically assessed with the intervals of characteristic increases in multiple-unit activity (MUA volleys) in the mediobasal hypothalamus. In estradiol-treated ovariectomized (OVX+E2) goats, the MUA volley intervals increased as fasting progressed. Plasma concentrations of non-esterified fatty acid and ketone body increased, while those of acetic acid and insulin decreased during fasting. The MUA volley intervals and plasma concentrations of those metabolites and insulin were restored to pre-fasting levels after subsequent refeeding. In ovariectomized (OVX) goats, changes in plasma metabolites and insulin concentrations were similar to those in OVX+E2 goats, but the MUA volley intervals were not altered. The present results demonstrated that fasting suppressed GnRH pulse generator activity in an estrogen-dependent manner. Changes in plasma concentrations of energy substrates and insulin during fasting were associated with the GnRH pulse generator activity in the presence of estrogen, but not in the absence of the steroid in female goats.
authors.affiliation: Laboratory of Neuroendocrinology, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Matsuyama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ohkura
authors.forename: Toru
authors.initials: T
authors.lastname: Ichimaru
authors.forename: Katsuyasu
authors.initials: K
authors.lastname: Sakurai
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tsukamura
authors.forename: Kei-ichiro
authors.initials: K
authors.lastname: Maeda
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Okamura
mesh_terms: D019342:Acetic Acid / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D004594:Electrophysiology; D004958:Estradiol / Q000378:metabolism; D005227:Fatty Acids / Q000097:blood; D005260:Female; D005508:Food Deprivation; D006041:Goats; D007987:Gonadotropin-Releasing Hormone / Q000097:blood / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D007659:Ketones / Q000097:blood; D010052:Ovariectomy; D010053:Ovary / Q000378:metabolism; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D005227:Fatty Acids; D007328:Insulin; D007659:Ketones; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D019342:Acetic Acid