Effect of L-dopa on interleukin-1 beta-induced suppression of luteinizing hormone secretion in intact female rats.
BACKGROUND
The cytokine, interleukin-1 beta (IL-1 beta), increases during immune stress and is known to suppress the preovulatory luteinizing hormone (LH) surge in female rats by decreasing hypothalamic norepinephrine (NE). We hypothesized that IL-1 beta could produce this effect by decreasing NE biosynthesis.


METHODS
Female Sprague-Dawley rats were implanted with a push-pull cannula in the medial preoptic area (MPA) of the hypothalamus and a catheter in the jugular vein. They were treated i.p. with the vehicle or 5 microg of IL-1 beta, the NE precursor, L-dopa, or a combination of L-dopa and IL-1 beta at 1300 hours on the day of proestrus. They were subjected to push-pull perfusion and serial blood sampling. Perfusates were analyzed for NE levels and serum samples for LH.


RESULTS
IL-1 beta treatment blocked the increase in NE levels in the MPA and the LH surge. Treatment with L-dopa was able to partially restore both NE and LH levels during the afternoon of proestrus. IL-1 beta treatment caused failure of ovulation and this effect was also reversed by L-dopa.


CONCLUSIONS
These results suggest that IL-1 beta could decrease NE levels in the MPA to suppress reproductive functions and L-dopa can be used to counter this effect.
Sirivelu
M P
MP
Comparative Medicine and Integrative Biology, College of Veterinary Medicine, Michigan State University, B-440 Life Sciences Building, East Lansing, MI 48824, USA.
Shin
A C
AC
Perez
G I
GI
MohanKumar
P S
PS
MohanKumar
S M J
SM
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D005260:Female; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D053583:Interleukin-1beta / Q000378:metabolism*; D007601:Jugular Veins; D007980:Levodopa / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D011301:Preoptic Area / Q000187:drug effects / Q000473:pathology; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D014621:Vagina / Q000378:metabolism
D053583:Interleukin-1beta; D007980:Levodopa; D007986:Luteinizing Hormone