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Oestradiol Stimulates the Release of AVP and GnRH from the Ewe Hypothalamus In Vitro 1
Author(s) -
Ghuman SPS,
Prabhakar S,
Smith RF,
Dobson H
Publication year - 2006
Publication title -
reproduction in domestic animals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.546
H-Index - 66
eISSN - 1439-0531
pISSN - 0936-6768
DOI - 10.1111/j.1439-0531.2006.00706.x
Subject(s) - endocrinology , medicine , hypothalamus , chemistry , basal (medicine) , in vivo , vasopressin , preoptic area , gonadotropin releasing hormone , in vitro , hormone , biology , biochemistry , luteinizing hormone , microbiology and biotechnology , insulin
Contents Oestradiol (E 2 ) sensitizes the stress and reproductive axes in vivo . Our current aim is to investigate whether E 2 directly influences hypothalamic AVP and GnRH release in vitro . Within 10 min of ewe killing, saggital midline hypothalamic slices (from the anterior preoptic area to mediobasal hypothalamus, 2 mm thick, two per sheep) were dissected, placed in oxygenated MEM‐ α at 4°C and within next 2 h were singly perifused at 37°C with oxygenated MEM‐ α (pH 7.4; flow rate 150 μ l/min) alone (vehicle; n = 15), with low (6 pg/ml; n = 14) or high E 2 (24 pg/ml; n = 13). After 5 h equilibration, 10 min fractions were collected for 3 h with exposure to 100 m m KCl for 10 min within the last hour. Concentrations of AVP and GnRH were measured by RIA. Baselines for AVP and GnRH were 7.0 ± 1.1 and 17.4 ± 0.8 pg/ml respectively. Basal values with low E 2 were similar to vehicle for AVP (7.5 ± 1.2 pg/ml) and GnRH (17.5 ± 1.1 pg/ml). However, high E 2 increased basal AVP (11.7 ± 1.4 pg/ml; p < 0.05) and GnRH (23.7 ± 1.4 pg/ml; p < 0.05). After KCl, AVP and GnRH respectively, increased (p < 0.05) to 25.6 ± 7.5 and 38.2 ± 5.6 (vehicle), 26.3 ± 7.5 and 23.6 ± 2.1 (low E 2 ) and 24.1 ± 5.4 and 41.3 ± 6.6 pg/ml (high E 2 ). After KCl, maximum values of AVP occurred at 20 and GnRH at 30 min. In conclusion, high E 2 concentration augments AVP and GnRH release by direct action on the ewe hypothalamus.