Central nervous blockade of oestradiol-stimulated release of luteinizing hormone in the ewe.

Abstract

SUMMARY The injection of oestradiol benzoate (OB) into the ovariectomized ewe induced a biphasic response in circulating luteinizing hormone (LH). There was a fall in concentration during the first 8–12 h after injection, and then a rapid increase in concentration during the next 12 h. Sodium pentobarbitone anaesthesia, begun either at the time of injection of OB, or 8 or 16 h later, did not affect the first phase, but prevented the second phase of this response. The injection of synthetic luteinizing hormone releasing factor caused a release of LH that was similar both in anaesthetized and conscious ewes. The results indicated a non-nervous site for the inhibitory action of oestrogen on circulating LH, and a central nervous site of action of oestrogen in stimulating LH release.