Artigo Revisado por pares

Progesterone-Sensitive Loci for Blockade of Ovulation in the Hamster

1973; Karger Publishers; Volume: 12; Issue: 1 Linguagem: Inglês

10.1159/000122151

ISSN

1423-0194

Autores

Lawrence A. Reuter, Robert D. Lisk,

Tópico(s)

Hypothalamic control of reproductive hormones

Resumo

Virgin female golden hamsters, 3-6 months old were implanted with progesterone, testosterone or cholesterol fused within the lumen of a hypodermic needle, or progesterone, cholesterol or paraffin fused into the end of a hypodermic tube or tungsten wire in order to determine progesterone-sensitive loci for blocking of ovulation. Molten steroid was drawn into 22-guage "thin wall", 27-guage 30-guage hypodermic tubing and then solidified. Large pellets (450 mcm) were made by dipping a 30-guage tube into molten steroid. Smaller pellets were made on the ends of tungsten wire (130 mcm). Pellets were measured on a shadowgraph to the nearest 10 mcm. The pellets were implanted through the top of the cranium and fastened with Kadon 22 dental cement. The implantation of 22-guage "thin wall" implants was performed 52-56 hours before ovulation and other implants 32-39 hours before the next expected ovulation. Hamsters were checked daily for ovulation by method of Orsini for 2 weeks after implantation. A hemi-ovarectomy and search for ova according to Reuter et al was performed on the day of their expected ovulation. The ovary was dissected and examined (10-30X magnification). The animals were sacrificed and brains removed, fixed in 10% formalin, serially sectioned at 100 mcm using a clinical freezing microtome, and stained with thronine to determine implantation site. Progesterone implants 18,000 sq. mcm larger resulted in blocking ovulation in the medial preoptic-diagonal band region of the hypothalamus. 28,000- 180,000 sq. mcm sizes also blocked ovulation when placed in the median eminence and in acurate nucleus regions of the hypothalamus but not in the hypophysis. The blocking effect of the hypophyseal implants can be explained by the lesion caused by the physical size of implants. Control substances did not block ovulation except when related to lesions caused by 450 mcm or 710 mcm diameter structures. Implants were effective in blocking ovulation for 2 weeks in larger implants and 1-3 days for smaller ones. The reason for this was not understood. Testosterone was also able to block ovulation in the medial preoptic-diagonal band region but to a significantly lesser degree than progesterone.

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