Chronic sympathetic stress increases acetylcholine levels and cholinesterase activity in rat ovary

[Speaker] Agustin Benitez:1
[Co-author] Fernanda Cuevas:1, Raul Riquelme:1, Hernan Lara:1
1:Universidad de Chile, Chile

The ovary is an endocrine organ responsible for folliculogenesis and steroidogenesis. Both processes are regulated by central and peripheral signals. It is well known that noradrenaline controls steroid secretion and ovarian follicular development. Its main source comes from extrinsic sympathetic neurons that innervate the organ. Emerging evidence suggest that acetylcholine enhances follicular development and, unlike noradrenaline, its production would be mainly in granulosa cells of large antral follicles (hence, intraovarian), which express choline acetyltransferase (ChAT) for acetylcholine synthesis. Besides, the presence of the cholinergic muscarinic receptors (M1, M3, M5) in the granulosa cells and acetylcholinesterase (AChE) in follicular fluid, suggests an autocrine/paracrine role for this neurotransmitter in follicular development. However, how this intraovarian cholinergic system is regulated remains unknown. Chronic cold stress is one of the pathological condition characterized by over-activity of sympathetic nerves without corticoids involvement. After the exposure to 4 weeks chronic cold stress there are changes in ovarian follicular development with a concomitant increment in the intraovarian neuronal growth factor (NGF). Interestingly, in vitro studies had shown that primary cultures of human granulose cells incubated with NGF increased ChAT protein. Thus, the objective of the present work was to determine the putative participation of the intraovarian cholinergic component that could be induced after 4 week cold stress. We used adult female Sprague-Dawley rats either control or exposed to cold stress (3 hours a day at 4 celsius degrees, 5 days a week) for 28 days. We determined levels of intraovarian acetylcholine and cholinesterase activity using a fluorometric assay, and levels of muscarinic receptors and acetylcholinesterase mRNA using RT-qPCR. We found that exposure to four week cold stress induces an increase in intraovarian acetylcholine content (p<0.05). Interestingly, it also produced an increment in cholinesterase activity and intraovarian mRNA levels of AChE (p<0.05). Altogether these data suggest that four week chronic cold stress stimulates intraovarian cholinergic components. Probably the increase in acetylcholine could be due to an increase of intraovarian NGF level as it has previously described. Further research is needed to establish the role of Ach in the follicular development.
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