Oxytocin augmentation of gonadotropin-releasing hormone-stimulated luteinizing hormone release is modulated by cyclic AMP

Hurd, Sarah; Evans, John J.; Mason, Drusilla

doi:10.1016/0024-3205(96)00357-8

Cited by 7 publications

(2 citation statements)

References 14 publications

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“…Oxytocin stimulation of LH release is believed to involve Ca 2+ [26, 27], inositol phosphates [26]and phosphoinositidase C [26]. There have been observations suggesting that reduced cAMP levels are associated with oxytocin-mediated enhancement of GnRH-stimulated LH release [28]. It is unknown if the cAMP-reducing abilities of NPY [29, 30]are involved in the regulation of LH release.…”

Section: Discussionmentioning

confidence: 99%

Release of Luteinizing Hormone from the Anterior Pituitary Gland in vitro Can Be Concurrently Regulated by at Least Three Peptides: Gonadotropin-Releasing Hormone, Oxytocin and Neuropeptide Y

2001

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Normal action of the female ovulatory cycle is dependent on a surge of luteinizing hormone (LH) from the pituitary. Regulation of the levels of LH is therefore vital to reproductive function. It has long been established that gonadotropin-releasing hormone (GnRH) is an important component of the regulatory processes. Other peptides, including oxytocin and neuropeptide Y (NPY), have also been observed to affect LH activities. However, the possibility of the concurrent actions of these peptides has rarely been considered despite their documented presence in the hypophyseal blood during pro-oestrus. In this study, the direct effects of oxytocin and NPY on LH release were studied, as well as the effects of both peptides simultaneously. Also, pituitaries were stimulated with GnRH, and the effects of pre-exposure of the pituitary tissue to oxytocin or NPY were investigated. Further, the effect of oxytocin and NPY together on GnRH stimulation of LH release was determined. Anterior pituitaries were collected from adult female rats on the morning of pro-oestrus. Hemipituitaries were cut in two and placed in a chamber of a perifusion system. The pituitary tissue was perifused with medium alone, oxytocin and NPY, separately or in combination, for 2 h after an initial 100-min equilibration period with no peptide present. Fractions of eluate were collected and LH was measured by radioimmunoassay. LH output was stimulated by both oxytocin (p < 0.01) and NPY (p < 0.02). Furthermore, the addition of NPY to oxytocin during the perifusion elicited a further increase in LH release (p < 0.05). The pituitary tissue was exposed to a 4-min pulse of GnRH after 220 min. Stimulation of LH release by GnRH was synergistically augmented by exposure of the tissue to either oxytocin (p < 0.01) or NPY (p < 0.05) for the immediately preceding 2 h. When NPY was added to oxytocin in the perifusion medium, stimulation of LH release by GnRH was increased even further (p < 0.05). Oxytocin also synergistically enhanced the effect of a second, primed GnRH pulse, whereas the effect of NPY was less robust. This study therefore demonstrated that LH release is modified in the presence of oxytocin, NPY or GnRH alone, and also that combinations of the peptides produce further variations in LH output. Therefore, the concentrations of LH that are present in vivo are likely to be at least partly the result of the co-ordinated effects of combinations of peptides acting on the pituitary.

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Section: Discussionmentioning

confidence: 99%

Release of Luteinizing Hormone from the Anterior Pituitary Gland in vitro Can Be Concurrently Regulated by at Least Three Peptides: Gonadotropin-Releasing Hormone, Oxytocin and Neuropeptide Y

2001

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“…We also noted that cycloheximide prevented GnRH self-priming in the absence [48] of galanin, and as mentioned above, the presence of galanin did not restore priming. Galanin may act to augment the GnRH-mediated response via a pathway activated also in priming [49]. The site of galanin action remains to be defined.…”

Section: Discussionmentioning

confidence: 99%

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

Peters

Towler²,

Mason³

et al. 2008

Neuroendocrinology

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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.

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Neuroendocrine Control of the Ovarian Cycle of the Rat

Levine

2015

Knobil and Neill's Physiology of Reproduction

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Oxytocin augmentation of gonadotropin-releasing hormone-stimulated luteinizing hormone release is modulated by cyclic AMP

Cited by 7 publications

References 14 publications

Release of Luteinizing Hormone from the Anterior Pituitary Gland in vitro Can Be Concurrently Regulated by at Least Three Peptides: Gonadotropin-Releasing Hormone, Oxytocin and Neuropeptide Y

Release of Luteinizing Hormone from the Anterior Pituitary Gland in vitro Can Be Concurrently Regulated by at Least Three Peptides: Gonadotropin-Releasing Hormone, Oxytocin and Neuropeptide Y

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

Neuroendocrine Control of the Ovarian Cycle of the Rat

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