beta-Endorphin plasma levels after intravenous administration of GnRH in female rats

Objective: The study investigates the effects of intravenously administered GnRH on plasma beta -endorphin levels in female proestrous rats. Study des ign: Sixteen adult female proestrous Wistar rats, 220-250 g, were implanted with two indwelling catheters, one intracarotid and one intrajugular. Ten ng GnRH/100 mul distilled water or 100 mul saline (control) were infused in eight animals per group every 20 min from 12:30 to 14:30 h. Blood was with drawn through the intracarotid catheter just before the initial infusion (1 2:30 h) and at 14:00, 15:30, 16:30 and 17:30 h for the determination of pla sma beta -endorphin levels. The Mann-Whitney test was used for comparison b etween GnRH-treated and control rats and the Wilcoxon test within each trea tment group. Results: beta -Endorphin levels of GnRH-treated rats were not significantly different at any sampling moment neither compared to preinfus ion time nor to the corresponding controls. Conclusions: Intravenously admi nistered GnRH was not sufficient for any possible effect on the secretion o f beta -endorphin from rat pituitary and further investigation is needed to demonstrate if a different experimental model would have any significant e ffect. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.