title: Histological characterization of gonadotropin-releasing hormone (GnRH) in the hypothalamus of the South American plains vizcacha (Lagostomus maximus).
abstract: In contrast to most mammalian species, females of the South American plains vizcacha, Lagostomus maximus, show an extensive suppression of apoptosis-dependent follicular atresia, continuous folliculogenesis, and massive polyovulation. These unusual reproductive features pinpoint to an eventual peculiar modulation of the hypothalamo-hypophyseal-gonadal axis through its main regulator, the gonadotropin-releasing hormone (GnRH). We explored the hypothalamic histological landscape and cellular and subcellular localization of GnRH in adult non-pregnant L. maximus females. Comparison to brain atlases from mouse, rat, guinea pig and chinchilla enabled us to histologically define and locate the preoptic area (POA), the ventromedial nucleus, the median eminence (ME), and the arcuate nucleus (Arc) of the hypothalamus in vizcacha's brain. Specific immunolocalization of GnRH was detected in soma of neurons at medial POA (MPA), ventrolateral preoptic nucleus, septohypothalamic nucleus (SHy) and Arc, and in beaded fibers of MPA, SHy, ventromedial hypothalamic nucleus, anterior hypothalamic area and ME. Electron microscopy examination revealed GnRH associated to cytoplasmic vesicles of the ME and POA neurons, organized both in core and non-core vesicles within varicosities, and in neurosecretory vesicles within the myelinated axons of the MPA. Besides the peculiar and unusual features of folliculogenesis and ovulation in the vizcacha, these results show that hypothalamus histology and GnRH immune-detection and localization are comparable to those found in other mammals. This fact leads to the possibility that specific regulatory mechanisms should be in action to maintain continuous folliculogenesis and massive polyovulation.
authors.affiliation: Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y Diagnóstico (CEBBAD), Universidad Maimónides, Hidalgo 775 6to piso, C1405BCK, Ciudad Autónoma de Buenos Aires, Argentina. dorfman.veronica@maimonides.edu
authors.forename: Verónica Berta
authors.initials: VB
authors.lastname: Dorfman
authors.forename: Nicolás
authors.initials: N
authors.lastname: Fraunhoffer
authors.forename: Pablo Ignacio Felipe
authors.initials: PI
authors.lastname: Inserra
authors.forename: César Fabián
authors.initials: CF
authors.lastname: Loidl
authors.forename: Alfredo Daniel
authors.initials: AD
authors.lastname: Vitullo
mesh_terms: D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D042541:Intracellular Space / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D012377:Rodentia / Q000378:metabolism*
chemical_list: D007987:Gonadotropin-Releasing Hormone