Intracerebroventricular injection of corticotropin-releasing hormone receptor antagonist blocks the suppression of pulsatile luteinizing hormone secretion induced by neuromedin U in ovariectomized rats after 48 hours of fasting.
We recently reported that neuromedin U (NMU) and fasting synergistically suppressed the pulsatile LH secretion, even though NMU has been shown to act as a satiety factor. In the present study, we examined whether this synergistic effect on the pulsatile LH secretion was mediated via corticotropin-releasing hormone (CRH) neurons. Adult ovariectomized (OVX) rats were stereotaxically implanted with a guide cannula into the third ventricle. After 2 weeks of recovery, blood samples were taken under freely-moving conditions at 6-min intervals for 180 min from 09:00 to 12:00 h in OVX rats that had been fasted for 48 h. After first 60 min of blood sampling, astressin (2 nmol/3 microl), a CRH receptor antagonist, dissolved in artificial cerebrospinal fluid (aCSF) or aCSF (3 microl) was injected as a control into the third ventricle. Thirty minutes after the first injection, the rats were injected with NMU (1 nmol/3 microl) into the third ventricle. We found that pre-treatment with astressin completely blocked the prolongation of the interpulse interval, which should be induced by NMU. We confirmed that a single intracerebroventricular injection of astressin per se did not affect the pulsatile LH secretion. The present study suggests that synergistic inhibitory effect of NMU and fasting on the pulsatile LH secretion is at least in part mediated via CRH neurons.
Quan
Hong
H
Department of Neuroendocrinology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan.
Funabashi
Toshiya
T
Kimura
Fukuko
F
D000704:Analysis of Variance; D000818:Animals; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D004347:Drug Interactions; D005215:Fasting / Q000097:blood*; D005260:Female; D007270:Injections, Intra-Articular / Q000379:methods; D007986:Luteinizing Hormone / Q000097:blood*; D009479:Neuropeptides / Q000494:pharmacology*; D010052:Ovariectomy / Q000379:methods; D010446:Peptide Fragments / Q000494:pharmacology*; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D018019:Receptors, Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors*; D013997:Time Factors
D009479:Neuropeptides; D010446:Peptide Fragments; D018019:Receptors, Corticotropin-Releasing Hormone; C056900:neuromedin U; C104416:astressin; D007986:Luteinizing Hormone; D003346:Corticotropin-Releasing Hormone