Effects of interleukin-1 beta on the steroid-induced luteinizing hormone surge: role of norepinephrine in the medial preoptic area.
Interleukin-1beta (IL-1beta), a cytokine, is known to inhibit the preovulatory surge of luteinizing hormone (LH); however, the mechanism by which it does so is unclear. This study was done to see if this effect is mediated through hypothalamic catecholamines. Adult female Sprague-Dawley rats were ovariectomized and implanted with a push-pull cannula in the medial preoptic area (MPA) of the hypothalamus. They were injected subcutaneously with 30 microg of Estradiol on the day 8 after surgery and with 2mg of Progesterone on day 10 at 1000 h. On the day of perfusion (day 10), the rats were injected with IL-1beta or its vehicle at 1300 h. Perfusate samples from the MPA and blood samples from a jugular catheter were collected from 1300 to 1800 h. Catecholamine concentrations in the perfusate were measured using high performance liquid chromatography (HPLC)-EC and LH levels in the serum using RIA. Norepinephrine release in the MPA of control rats increased significantly at 1530, 1600, and 1630 h paralelling an increase in LH at 1600 h. In contrast, IL-1beta treatment blocked the LH surge and the rise in norepinephrine release in the MPA. No changes were observed in dopamine release, both in control and IL-treated animals. These results demonstrate for the first time that IL-induced suppression of the LH surge is probably mediated through inhibition of norepinephrine release in the MPA.
Neuroendocrine Research Laboratory, Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA. mohankumrs@ahdl.msu.edu
Sheba M J
SM
MohanKumar
P S
PS
MohanKumar
D000818:Animals; D005260:Female; D007375:Interleukin-1 / Q000494:pharmacology* / Q000502:physiology; D007986:Luteinizing Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D010052:Ovariectomy; D011301:Preoptic Area / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D007375:Interleukin-1; D007986:Luteinizing Hormone; D009638:Norepinephrine