title: Immunohistochemical evidence for the relationship between microglia and GnRH neurons in the preoptic area of ovariectomized rats with and without steroid replacement.
abstract: Prostaglandins (PGs), whose synthesis is catalyzed by the rate-limiting enzyme cyclooxygenase (COX) including COX-1 and COX-2, are among the important mediators involved in the regulation of gonadotropin-releasing hormone (GnRH) secretion. However, the cellular origin of PGs remains obscure in terms of its relationship to GnRH neurons. The present study was therefore aimed to clarify the anatomical relationship between COX-1-producing microglia and GnRH neurons in the preoptic area (POA), and to examine possible influence of ovarian steroids. We performed a triple labeled immunofluorescent histochemistry of COX-1, CD11b (a specific marker for microglia) and GnRH in the POA of ovarian steroid-primed and non-primed ovariectomized rats. The result confirmed our previous study suggesting COX-1 immunoreactivity in the vicinity of, but not within, GnRH neurons in the POA. COX-1 around GnRH cells was entirely (100%) localized in cells containing CD11b regardless of steroid replacement in ovariectomized rats. These CD11b-immunoreactive cells had small cell bodies and highly branched fibers characteristic of ramified microglia. Three-dimensional reconstruction of confocal images revealed close proximity of some COX-1-containing microglia and GnRH neurons. These results showed selective and constitutive expression of COX-1 in ramified microglia in the vicinity of GnRH neurons, providing evidence for intercellular communication, mediated by PGs, from microglia to GnRH cells.
authors.affiliation: Department of Physiology, St. Marianna University School of Medicine, Kawasaki 216-8511, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Fujioka
authors.forename: Chiaki
authors.initials: C
authors.lastname: Kakehashi
authors.forename: Toshiya
authors.initials: T
authors.lastname: Funabashi
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Akema
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D039481:CD11b Antigen / Q000378:metabolism; D002450:Cell Communication / Q000187:drug effects*; D048430:Cell Shape / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D051545:Cyclooxygenase 1 / Q000378:metabolism*; D015914:Estrogen Replacement Therapy; D005260:Female; D005455:Fluorescent Antibody Technique; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D017628:Microglia / Q000166:cytology / Q000378:metabolism*; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010052:Ovariectomy / Q000009:adverse effects; D011301:Preoptic Area / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D015415:Biomarkers; D039481:CD11b Antigen; D009419:Nerve Tissue Proteins; D007987:Gonadotropin-Releasing Hormone; D051545:Cyclooxygenase 1