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Three‐dimensional properties of GnRH neuroterminals in the median eminence of young and old rats
Author(s) -
Yin Weiling,
Mendenhall John M.,
Monita Monique,
Gore Andrea C.
Publication year - 2009
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.22156
Subject(s) - median eminence , biology , ganglionic eminence , ovariectomized rat , context (archaeology) , arcuate nucleus , terminal nerve , gonadotropin releasing hormone , medicine , endocrinology , hypothalamus , anatomy , hormone , central nervous system , luteinizing hormone , paleontology , cerebrum
The decapeptide gonadotropin‐releasing hormone (GnRH), which regulates reproduction in all vertebrates, is stored in, and secreted from, large dense‐core secretory vesicles in nerve terminals in the median eminence. GnRH is released from these terminals with biological rhythms that are critical for the maintenance of normal reproduction. During reproductive aging in female rats, there is a loss of GnRH pulses and a diminution of the GnRH surge. However, information about the specific role of GnRH nerve terminals is lacking, particularly in the context of aging. We sought to gain novel ultrastructural information about GnRH neuroterminals by performing three‐dimensional (3D) reconstructions of GnRH neuroterminals and their surrounding microenvironment in the median eminence of young (4–5 months) and old (22–24 months) ovariectomized Sprague–Dawley female rats. Median eminence tissues were freeze‐plunge embedded and serial ultrathin sections were collected on slot grids for immunogold labeling of GnRH immunoreactivity. Sequential images were used to create 3D models of GnRH terminals. These reconstructions provided novel perspectives into the morphological properties of GnRH terminals and their neural and glial environment. We also noted that the cytoarchitectural features of the median eminence became disorganized with aging. Quantitative measures showed a significant decrease in the apposition between GnRH terminal membranes and glial cells. Our data suggest reproductive aging in rats is characterized by structural organizational changes to the GnRH terminal microenvironment in the median eminence. J. Comp. Neurol. 517:284–295, 2009. © 2009 Wiley‐Liss, Inc.