Introduction lactational behavior, production of ova and hormones
Brain Research 887 2000 70–79 www.elsevier.com locate bres
Research report
Effect of food deprivation and leptin repletion on the plasma levels of estrogen E2 and NADPH-d reactivity in the ventromedial and
arcuate nuclei of the hypothalamus in the female rats
a , a
a b
Effiong Edet Otukonyong , Fumino Okutani , Seiichi Takahashi , Takuya Murata ,
c a
b
Nobuyuki Morioka , Hideto Kaba , Takashi Higuchi
a
Department of Physiology , Kochi Medical School, Nankoku, Kochi 783-8505, Japan
b
Department of Physiology , Fukui Medical University, Matsuoka, Fukui 910-1193, Japan
c
Department of Obstetrics and Gynecology , Kochi Medical School, Nankoku, Kochi 783-8505, Japan
Accepted 12 September 2000
Abstract
The exact role of leptin in fasting has not been completely elucidated. To determine whether leptin can act in fasting to influence plasma estrogen levels and nitric oxide synthase reactivity in food regulating centers of the brain, we fasted female rats for 4 days and
treated them i.p. with vehicle or 100 mg of recombinant mouse leptin as 1 ml on the 3rd and 4th day twice daily 10.00 and 17.00 h. Proestrus blood was collected at 10.00, 14.00, 18.00 and at 22.00 h, plasma obtained and assayed for estrogen E2 and leptin levels.
Verification of ovulation occurrence was by examining the oviduct for extruded ovum. The rat brains were removed and processed for nitric oxide synthase reactivity in the ventromedial hypothalamus VMH and arcuate nucleus ARC using NADPH-diaphorase
histochemistry, a marker for neurons expressing NOS enzyme. Leptin effect on dependable variables such as food intake, water intake and body weight gain was also investigated. Four days fasting significantly decreased body weight, estrogen and postfast leptin levels, nitric
oxide reactivity in the VMH and ARC nucleus and stopped ovulation in many 4 out of 5 rats fasted and given vehicle. Leptin treatment significantly increased plasma estrogen and postfast leptin levels, restored ovulation in many 4 out of 5 rats and increased nitric oxide
reactivity in the VMH and ARC. Leptin significantly inhibited food intake, water intake and gain in body weight during recommenced feeding. These observations suggest that leptin could act in the pituitary–ovarian axis during fasting to improve reproductive function by
partly stimulating estrogen secretion.
2000 Elsevier Science B.V. All rights reserved.
Theme : Endocrine and autonomic regulation
Topic : Hypothalamic–pituitary–gonadal regulation
Keywords : Arcuate nucleus; Estrogen; Fasting; Leptin; Nitric oxide synthase; Ventromedial hypothalamus