Sexual dimorphism in copackaging of luteinizing hormone-releasing hormone and galanin into neurosecretory vesicles of hypophysiotrophic neurons: Estrogen dependency

Z. Liposits, J. J. Reid, A. Negro-Vilar, I. Merchenthaler

Research output: Contribution to journalArticle

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Abstract

Hypophysiotrophic neurons projecting to hypophyseal portal vessels in the median eminence of the hypothalamus maintain the operation of the master gland, the pituitary, by secreting releasing and release-inhibiting hormones into the bloodstream. LHRH, synthesized in neurons of the rat prosencephalon, is one of the key substances that governs the anterior pituitary-gonadal axis. Recently, it has been shown that the peptide galanin (GAL) is coproduced in a subpopulation of LHRH neurons and is a potent modulator of central processes regulating reproduction. A better understanding of the secretory mechanisms involved in pulsatile hormone release from LHRH axons of the median eminence requires exploration of the organelle domain that displays the cosynthesized peptides in terminal boutons. This study shows that LHRH- and GAL-immunoreactive axons overlap heavily in the lateral part of the median eminence. Double fluorescent labeling revealed colocalization of the peptides at the level of single axon terminals. By means of dual colloidal gold immunolabeling, LHRH and GAL were detected in the same secretory vesicles at the ultrastructural level. The incidence of colocalizing vesicles was high in the female (45%) and low in the male (3%) rat. Ovariectomy resulted in a dramatic decline in the number of LHRH/GAL- coexpressing vesicles (23%), which was reversed (55%) by the administration of estradiol. The observations indicate a sex-related difference in the packaging of LHRH and GAL and suggest that the events are estrogen dependent. Furthermore, the simultaneous release of GAL and LHRH from the colocalizing vesicles provides a mechanism that might ensure the potentiating effect of GAL on LHRH by synchronizing events at the receptor sites in the anterior pituitary.

Original languageEnglish
Pages (from-to)1987-1992
Number of pages6
JournalEndocrinology
Volume136
Issue number5
Publication statusPublished - 1995

Fingerprint

Galanin
Gonadotropin-Releasing Hormone
Sex Characteristics
Estrogens
Neurons
Median Eminence
Peptides
Axons
Hormones
Gold Colloid
Presynaptic Terminals
Secretory Vesicles
Ovariectomy
Product Packaging
Pituitary Gland
Prosencephalon
Organelles
Hypothalamus
Reproduction
Estradiol

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Sexual dimorphism in copackaging of luteinizing hormone-releasing hormone and galanin into neurosecretory vesicles of hypophysiotrophic neurons : Estrogen dependency. / Liposits, Z.; Reid, J. J.; Negro-Vilar, A.; Merchenthaler, I.

In: Endocrinology, Vol. 136, No. 5, 1995, p. 1987-1992.

Research output: Contribution to journalArticle

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abstract = "Hypophysiotrophic neurons projecting to hypophyseal portal vessels in the median eminence of the hypothalamus maintain the operation of the master gland, the pituitary, by secreting releasing and release-inhibiting hormones into the bloodstream. LHRH, synthesized in neurons of the rat prosencephalon, is one of the key substances that governs the anterior pituitary-gonadal axis. Recently, it has been shown that the peptide galanin (GAL) is coproduced in a subpopulation of LHRH neurons and is a potent modulator of central processes regulating reproduction. A better understanding of the secretory mechanisms involved in pulsatile hormone release from LHRH axons of the median eminence requires exploration of the organelle domain that displays the cosynthesized peptides in terminal boutons. This study shows that LHRH- and GAL-immunoreactive axons overlap heavily in the lateral part of the median eminence. Double fluorescent labeling revealed colocalization of the peptides at the level of single axon terminals. By means of dual colloidal gold immunolabeling, LHRH and GAL were detected in the same secretory vesicles at the ultrastructural level. The incidence of colocalizing vesicles was high in the female (45{\%}) and low in the male (3{\%}) rat. Ovariectomy resulted in a dramatic decline in the number of LHRH/GAL- coexpressing vesicles (23{\%}), which was reversed (55{\%}) by the administration of estradiol. The observations indicate a sex-related difference in the packaging of LHRH and GAL and suggest that the events are estrogen dependent. Furthermore, the simultaneous release of GAL and LHRH from the colocalizing vesicles provides a mechanism that might ensure the potentiating effect of GAL on LHRH by synchronizing events at the receptor sites in the anterior pituitary.",
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