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
Abstract
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 tha...Continue Reading
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