Retrograde labeling of hypophysiotropic neurons by local injection of wheat germ agglutinin (WGA) into the median eminence or peripheral administration of fluoro-gold.

The localization of neuronal perikarya which have axon terminals on capillaries of the external zone of the median eminence (hypophysiotropic neurons) has been determined in the rat after injection of wheat germ agglutinin (WGA) directly into external zone of the median eminence or after peripheral injection of Fluoro-Gold. The retrogradely transported WGA and endogenous peptides (luteinizing hormone-releasing hormone, somatostatin, galanin, or neurotensin) have been detected by double-labeling immunocytochemical techniques (PAP or ABS) using contrasting chromogens. Retrograde labeling with Fluro-Gold has been combined with fluoroscence immunocuytochemistry, using Texas red as the second chromogen. A few examples of triple labeling (Fluoro-Gold and two endogenous peptides) are also demonstrated. Detailed descriptions of double-labeling techniques, including preparation and administration of the tracers and simultaneous detection of the retrograde tracers and endogenous peptides, are presented.