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.
MohanKumar
Sheba M J
SM
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
MohanKumar
P S
PS
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