Intracerebroventricular leptin injection affects neuroendocrine reproductive axis in ovariectomized rats

【摘要】 BACKGROUND:Leptin regulates neuroendocrine function of the hypothalamus-pituitary-ovary axis in humans. OBJECTIVE: To verify effects of intracerebroventricular leptin injection on neuroendocrine function of the hypothalamus-pituitary-ovary axis in ovariectomized rats. DESIGN, TIME AND SETTING: A randomized, controlled experiment was performed at the Basic Medical Institute, Chengde Medical College between June and October 2007. MATERIALS: Thirty healthy, female, Wistar rats were included in this study. The following compounds were used: leptin; gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) enzyme-linked immunosorbent assay kits. METHODS: Rats were randomly divided into 3 groups at 1, 2, and 4 hours after injection. Each group was subdivided into control and experimental groups (n = 5 animals per group and time point). All rats were subjected to bilateral ovariectomy and, beginning on day 7 after surgery, animals received daily subcutaneous injections of estradiol benzoate (2 μg) for 7 consecutive days. The experimental groups were injected with 5 μL leptin (1 g/L) into the lateral cerebral ventricle, and control groups received an equal volume of physiological saline. MAIN OUTCOME MEASURES: GnRH and LH secretion were examined 1, 2, and 4 hours after injection using GnRH and LH ELISA kits, respectively. RESULTS: In the experimental groups, GnRH secretion significantly increased (P < 0.01), followed by LH secretion (P < 0.01), compared with the control groups. GnRH secretion significantly increased 1 hour after leptin injection (P < 0.01). The LH increase was less pronounced, but still significant (P < 0.01); however, the most prominent LH increase occurred between 1 and 2 hours. Both GnRH and LH secretion reached peak levels at 2 hours after leptin injection. Thereafter, both GnRH and LH secretion decreased, but still maintained very high levels, compared with the control group (P < 0.01). CONCLUSION: Intracerebroventricular leptin injection produced similar effects on GnRH and LH secretion in ovariectomized rats, indicating regulatory effects of leptin on GnRH and LH secretion.更多还原

【Abstract】 BACKGROUND: Leptin regulates neuroendocrine function of the hypothalamus-pituitary-ovary axis in humans. OBJECTIVE: To verify effects of intracerebroventricular leptin injection on neuroendocrine function of the hypothalamus-pituitary-ovary axis in ovariectomized rats. DESIGN, TIME AND SETTING: A randomized, controlled experiment was performed at the Basic Medical Institute, Chengde Medical College between June and October 2007. MATERIALS: Thirty healthy, female, Wistar rats were included in this study. The following compounds were used: leptin; gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) enzyme-linked immunosorbent assay kits. METHODS: Rats were randomly divided into 3 groups at 1, 2, and 4 hours after injection. Each group was subdivided into control and experimental groups (n = 5 animals per group and time point). All rats were subjected to bilateral ovariectomy and, beginning on day 7 after surgery, animals received daily subcutaneous injections of estradiol benzoate (2 μg) for 7 consecutive days. The experimental groups were injected with 5 μL leptin (1 g/L) into the lateral cerebral ventricle, and control groups received an equal volume of physiological saline. MAIN OUTCOME MEASURES: GnRH and LH secretion were examined 1, 2, and 4 hours after injection using GnRH and LH ELISA kits, respectively. RESULTS: In the experimental groups, GnRH secretion significantly increased (P < 0.01), followed by LH secretion (P < 0.01), compared with the control groups. GnRH secretion significantly increased 1 hour after leptin injection (P < 0.01). The LH increase was less pronounced, but still significant (P < 0.01); however, the most prominent LH increase occurred between 1 and 2 hours. Both GnRH and LH secretion reached peak levels at 2 hours after leptin injection. Thereafter, both GnRH and LH secretion decreased, but still maintained very high levels, compared with the control group (P < 0.01). CONCLUSION: Intracerebroventricular leptin injection produced similar effects on GnRH and LH secretion in ovariectomized rats, indicating regulatory effects of leptin on GnRH and LH secretion.更多还原