Effect of Stress in the Ovarian Cholinergic System, the Ovarian Function and the Fertility in the Rat

[Speaker] Raul Riquelme:1
[Co-author] Hernan Lara:1
1:Neurobiochemistry, Universidad de Chile, Chile

The mammalian ovary control steroids biosynthesis and follicular development. Polycystic Ovarian Syndrome (PCOS), presents an aberrant follicular development, hyperandrogenism and in most of the cases infertility. An increase in sympathetic tone by chronic exposure to cold stress induces a phenotype similar to polycystic ovarian condition but no information exist about the impact in fertility. Cholinergic system activation by pharmacological increase in ovarian acetylcholine (ACh) by local inhibition of acetylcholinesterase, increased follicular development and fertility on the rat. The purpose of this work was to determine the effects of cold stress on the cholinergic system and its relation with rat's fertility. Female Sprague-Dawley rats were exposed to cold stress during 28 days (4C, during 3 h/day) to activate the autonomic nerves. They were followed by another 28 days period without stress, to verify the nerve activation and its relation with cysts development and fertility in the rats. At the end of each period, we measured plasma levels of steroids (enzyme immunoassay). For follicular development, we did a morphometric analysis of hematoxilin-eosine stained slices. To verify sympathetic and cholinergic system we measured NA and ACh. Fertility was determined by the capacity of the experimental rats to maintain a cyclic ovulatory performance and to get pregnant. Stress increased both NA and ACh ovary levels but returned to control after the 28 additional days of observation. Stress decreased the number of secondary and antral follicles but increases follicular atresia and continued decreasing after the 28 additional days. The number of corpora lutea decreased and presented a profound decrease after the additional 28 days of observation. Cystic follicles did not change after the first period of stress but increased after the second 28 days period of observation. Steroids plasma levels confirmed the aberrant follicular development. Increased testosterone (hyperandrogenism), and estradiol. Progesterone however, decreased confirming the decrease in ovulation (and hence in the number of corpora lutea). Regarding fertility, there was a constant decrease in the ovulatory performance verified by the irregular estrual cycling activity suggesting that all of the changes found in the ovary, triggered by stress, and closely correlated to ovary function.
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