Ovarian steroid modulation of norepinephrine action on luteinizing hormone release. Analogous effects in male and female rats.

The modulatory actions of ovarian steroids on the norepinephrine (NE) induced alterations in luteinizing hormone (LH) secretion were examined in male and female rats. Long-term (4 weeks) castrated male and female rats bearing chronic third-ventricle cannulae were implanted with intra-atrial catheters. Animals were bled sequentially at 5- or 15-min intervals for 4-6 h, and plasma LH secretory patterns were determined by radioimmunoassay. After a 2- to 3-hour control bleeding period, castrated unprimed rats received an intracerebroventricular (ICV) infusion of 0.3 mumol of arterenol bitartrate or vehicle. Blood sampling was continued for an additional 2-3 h after infusion. In female rats NE caused a rapid and potent inhibition of episodic LH secretion which was characterized by decreases in mean plasma LH, mean pulse amplitude, and pulse frequency. Similarly, ICV infusion of NE into male rats resulted in decreased mean plasma LH and pulse frequency. In a second series of experiments, castrated male and female rats were primed with estrogen and progesterone 2 days prior to the bleeding/infusion session. Animals were bled sequentially and infused with 0.3 mumol arterenol bitartrate or vehicle during a morning or afternoon session. ICV infusion of vehicle had no effect on plasma LH in either sex regardless of the time of day. NE infusion into estrogen and progesterone primed female rats resulted in significant elevations of plasma LH during both morning and afternoon periods. In estrogen and progesterone primed male rats, NE infusion resulted in a marked facilitation of LH release, similar to that observed in female rats.(ABSTRACT TRUNCATED AT 250 WORDS)