Effects of Galanin and Leptin on Gonadotropin-Releasing Hormone-Stimulated Luteinizing Hormone Release from the Pituitary

Abstract

Background: A number of peptides regulate luteinizing hormone (LH) release. In some cases, these peptides exert an effect at the pituitary, to directly regulate LH release and/or to modulate the effects of gonadotropin-releasing hormone (GnRH). A link between nutrition and reproductive function is well established. In this study we investigated the effects of two peptides associated with appetite control, galanin and leptin, on the regulation of LH release from the pituitary. Methods: Using perifused anterior pituitary tissue from freely fed rats, we investigated the effect of galanin on basal LH release and GnRH-stimulated LH release from pituitaries in a high-estrogen (proestrus) and a low-estrogen (metestrus) environment. In addition, we examined the effect of galanin on LH release following GnRH self-priming. The effect of inhibiting protein synthesis, with cycloheximide, was also studied under these conditions. Finally, the effects of leptin alone and on a galanin-modulated LH response were investigated. Results: There was no detectable effect of leptin, either alone or in conjunction with galanin. We observed that galanin enhanced GnRH stimulation of LH secretion, an effect that was dependent on protein synthesis and on an estrogenized environment. In addition, importantly, galanin also enhanced the LH response in GnRH self-primed pulses. Conclusion: Our results provide further details on the effect of galanin on the LH surge, particularly the effect on the response to pulsatile GnRH and the effect of protein production, and thereby indicate a means by which appetite- and nutrition-related peptides may act on the ovulatory cycle at the pituitary.

In vitro effect of leptin on anterior pituitary cells LH secretory activity during early pregnancy in pig

“…Furthermore, stimulatory influence of leptin on GnRH-induced LH release from AP pituitary cells was reported in juvenile (Tezuka et al 2002) and pubertal (Ogura et al 2001) rats and observed effect expressed as a bell-shaped dose-response curve. No leptin activity was found in respect to the In vitro effect of leptin on anterior pituitary cells LH...modulation of LH release from GnRH-activated hemi-anterior pituitaries of adult male (Yu et al 1997) as well as proestrus rats (Peters et al 2009). Leptin was also shown to enhance GnRH-mediated secretion of LH from AP explants of normal-fed, but not of fasted, cows (Amstalden et al 2003).…”

The regulative effect of galanin family members on link of energy metabolism and reproduction

“…On the one hand, galanin can stimulate LH secretion directly or indirectly via enhancing the estrogen-dependent GnRH role in hypothalamus and pituitary gland of rats and young male calves [105,129], which may be blocked by low levels of estradiol [11,105,163] or i.c.v. administration of galanin antagonist galantide in rats [54,126,152].…”

Direct Evidence for the Co-Expression of URP and GnRH in a Sub-Population of Rat Hypothalamic Neurones: Anatomical and Functional Correlation

“…Taking together these data, we can hypothesize that URP would modulate the secretion of GnRH from nerve terminals in the median eminence, as it has been described for the co-expressed neuropeptide galanin [9], [29], [30]. The mechanisms underlying the regulation of GnRH neurones by galanin remain still unknown.…”