title: Food availability affects orexin a/ hypocretin-1-induced inhibition of pulsatile luteinizing hormone secretion in female rats.
abstract: Orexin A/hypocretin-1 inhibits pulsatile luteinizing hormone (LH) secretion in female rats. In this study, we investigated whether this inhibition was tied to the fasting state, as suggested by our previous study. We first examined whether orexin A inhibited pulsatile LH secretion when food was available ad libitumduring blood sampling. Next, we investigated the effect of intravenous administration of glucose (400 mg/kg) or lactic acid (negative control; 400 mg/kg) on orexin A-induced inhibition of pulsatile LH secretion. We found that orexin A did not affect pulsatile LH secretion in the presence of food, although it increased feeding behavior. Injection of orexin A significantly inhibited pulsatile LH secretion when food was withheld during blood sampling (p < 0.05); this inhibitory effect was rapidly reversed by intravenous injection of glucose but not lactic acid. Because orexin A did not seem to affect pulsatile LH secretion when food was available ad libitum, we speculate that orexin A has an effect on LH secretion when orexin A-induced hunger is accompanied by stress, such as the absence of food. Furthermore, glucose as well as food may act as a satiety factor in gonadotropin-releasing hormone pulse generation.
authors.affiliation: Department of Physiology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
authors.forename: Miyako
authors.initials: M
authors.lastname: Furuta
authors.forename: Dai
authors.initials: D
authors.lastname: Mitsushima
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Shinohara
authors.forename: Fukuko
authors.initials: F
authors.lastname: Kimura
authors.forename: Toshiya
authors.initials: T
authors.lastname: Funabashi
mesh_terms: D000818:Animals; D005215:Fasting / Q000097:blood / Q000378:metabolism*; D005247:Feeding Behavior / Q000502:physiology; D005260:Female; D005947:Glucose / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D000068797:Orexins; D010507:Periodicity; D051381:Rats; D017208:Rats, Wistar; D012528:Satiety Response / Q000502:physiology; D013315:Stress, Psychological / Q000097:blood / Q000378:metabolism; D013997:Time Factors
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D019344:Lactic Acid; D007986:Luteinizing Hormone; D005947:Glucose