Bombesin inhibits LH release in ovariectomized (OVX), estrogen primed rats

OBJECTIVE: Bombesin, 14-amino acid peptide, discovered in the gastrointestinal tract, is widely distributed in the central nervous system (CNS). The specific receptors of bombesin in the pituitary have been characterized. Bombesin plays an important role in the gastric and pancreatic secretion, in the mechanism of food intake, thermoregulation and in pituitary hormone secretion. There are contentious opinions about the effect of bombesin on hormone secretion. THE AIM: The aim of this study was to evaluate the effect of estrogens in the modulation of bombesin action on LH release. RESEARCH METHODS: Female Wistar-Kyoto rats, two weeks after ovariectomy (OVX), were implanted with a cannula being located in the third cerebroventricle. Thereafter, the rats were primed with 17 beta estradiol in a dose of 25 mu g/0.2ml s.c. for three consecutive days. On the day of the experiment, bombesin at a concentration of 0.5 mu g in 5 mu l vehicle (artificial cerebrospinal fluid) or equal volume of the vehicle was infused into the third ventricle with an automatic pump. At 60 or 120 min after the infusion the animals were decapitated, and the trunk blood was collected. Rat serum LH was measured by RIA kit supplied by Dr A.F. Parlow from NIDDK Baltimore, MD. RESULTS: Bombesin inhibited LH release at 120 min and it did not change LH release at 60 min after icv administration. CONCLUSIONS: The response of LH release after central injection of bombesin is modified by estrogens.