Ultrastructural localization of galanin immunoreactivity in the rat median eminence

The aim of this study was to examine, by use of a pre-embedding immunoperoxidase technique, the ultrastructural localization of galanin immunoreactivity in the external layer of the rat median eminence. Galanin immunoreactivity was only observed in axonal profiles. Immunoreactive fibers were found in contact with the following non-immunoreactive structures: (1) axonal profiles that contain dense granular vesicles and clear vesicles, (2) axonal profiles that contain predominantly clear vesicles, (3) glial cell bodies, and (4) processes of tanycytes. Labeled terminals were also observed in the proximity of the perivascular space of the portal vessels. The results suggest possible interactions between galanin-immunoreactive terminals and other terminals containing peptide and/or other transmitters in the external layer of the median eminence.