title: Concentrations of estradiol in ewe cerebrospinal fluid are modulated by photoperiod through pineal-dependent mechanisms.
abstract: 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.
authors.affiliation: UMR INRA-CNRS-Université de Tours, Physiologie de la Reproduction et des Comportements, Nouzilly, France. thiery@tours.inra.fr
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Thiery
authors.forename: Didier
authors.initials: D
authors.lastname: Lomet
authors.forename: Michael
authors.initials: M
authors.lastname: Schumacher
authors.forename: Philippe
authors.initials: P
authors.lastname: Liere
authors.forename: Helene
authors.initials: H
authors.lastname: Tricoire
authors.forename: Alain
authors.initials: A
authors.lastname: Locatelli
authors.forename: Philippe
authors.initials: P
authors.lastname: Delagrange
authors.forename: Benoit
authors.initials: B
authors.lastname: Malpaux
mesh_terms: D000818:Animals; D004958:Estradiol / Q000097:blood / Q000134:cerebrospinal fluid* / Q000528:radiation effects*; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood / Q000134:cerebrospinal fluid; D008550:Melatonin / Q000097:blood / Q000134:cerebrospinal fluid; D010052:Ovariectomy; D017440:Photoperiod; D010870:Pineal Gland / Q000502:physiology* / Q000528:radiation effects* / Q000601:surgery; D012756:Sheep
chemical_list: D004958:Estradiol; D007986:Luteinizing Hormone; D008550:Melatonin