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Concentrations of estradiol in ewe cerebrospinal fluid are modulated by photoperiod through pineal‐dependent mechanisms
Author(s) -
Thiery JeanClaude,
Lomet Didier,
Schumacher Michael,
Liere Philippe,
Tricoire Helene,
Locatelli Alain,
Delagrange Philippe,
Malpaux Benoit
Publication year - 2006
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.2006.00370.x
Subject(s) - pinealectomy , pineal gland , endocrinology , medicine , melatonin , cerebrospinal fluid , photoperiodism , ovariectomized rat , hypothalamus , luteinizing hormone , biology , cannula , hormone , estrous cycle , surgery
In the ewe, seasonal anestrus results from an increased responsiveness of the hypothalamus to the negative feedback of estradiol (E2) on the gonadotropic axis under long‐day conditions. However, this seasonal effect could also depend upon variable uptake of steroids by the brain. The aim of the present experiment was to compare the concentration of E2 in the blood plasma and in the cerebrospinal fluid (CSF) from the third ventricle in groups of ovariectomized, estradiol treated ewes maintained under short day (SD) or long day (LD) conditions and to study the involvement of the pineal gland in this photoperiodic regulation. Pinealectomized and sham‐operated ewes were equipped with an intracerebral cannula to sample the CSF. The plasma E2 concentrations showed no difference between LD and SD in sham‐operated and pinealectomized animals. In contrast, in the CSF, E2 concentration was higher in the LD than the SD group, and pinealectomy suppressed this effect of photoperiod. Concomitantly, the stimulatory effect of SD on luteinizing hormone levels observed in sham‐operated ewes was abolished by pinealectomy. The results demonstrate that LD increases the E2 concentration in the CSF by a mechanism involving the pineal gland.