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 between gonadotropin-releasing hormone (GnRH) nerve terminals and gap junctions in the median eminence. Coronal brain sections from castrated male rats were dual immunostained with GnRH and either connexin 26, 32, or 43, and examined by confocal laser microscopy. Connexin 43-immunoreactive puncta were distributed between GnRH-immunoreactive fibers, and some of them were colocalized with GnRH-immunoreactivities. Dual immunostaining with connexin 43 and glial fibrillary acidic protein revealed that most of the puncta were located in astrocytes. At the immunoelectron microscopic level, connexin 43-immunoreactivities 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.