Morphological characterization of relationship between gap junctions and gonadotropin releasing hormone nerve terminals in the rat median eminence

The present study aimed to reveal possible morphological relationships betw een gonadotropin-releasing hormone (GnRH) nerve terminals and gap junctions in the median eminence. Coronal brain sections from castrated male rats we re dual immunostained with GnRH and either connexin 26, 32, or 43, and exam ined by confocal laser microscopy. Connexin 43-immunoreactive puncta were d istributed between GnRH-immunoreactive fibers, and some of them were coloca lized with GnRH-immunoreactivities. Dual immunostaining with connexin 43 an d glial fibrillary acidic protein revealed that most of the puncta were loc ated in astrocytes. At the immunoelectron microscopic level, connexin 43-im munoreactivities were mainly located on the plasma membranes of glial-like processes. Few connexin 26- or connexin 32-immunoreactivities were found in the median eminence. The present results indicate the possibility that gap junctions play a. role in the GnRH release at the median eminence. (C) 199 9 Elsevier Science Ireland Ltd. All rights reserved.