Galanin-immunoreactive axons innervate somatostatin-synthesizing neurons in the anterior periventricular nucleus of the rat

Endocrinology. 1993 Feb;132(2):917-23. doi: 10.1210/endo.132.2.7678803.


The anterior periventricular nucleus (PeN) regulates GH secretion by synthesizing and releasing somatotropin release-inhibiting factor (SRIF) into the portal circulation. This territory of the diencephalon is heavily innervated by axons of galanin (GAL)-immunoreactive (IR) neurons. The connections between GAL-IR fibers and hypophysiotropic SRIF neurons were studied by means of immunocytochemical double labeling at the light and electron microscopic levels. Retrograde axonal labeling with Fluoro-Gold revealed the anterior PeN as the main site of hypophysiotropic SRIF-synthesizing neurons. These cells were densely surrounded by GALergic axons that made contacts with their cell bodies and dendrites. At the ultrastructural level, diaminobenzidine-labeled SRIF neurons received synapsing GAL-IR axons marked with silver-gold particles. Both axo-somatic and axo-dendritic forms of connections were observed. These morphochemical data revealed an interaction between GAL- and SRIF-synthesizing neurons in the anterior PeN. Furthermore, the presence of synaptic connections between these neuronal systems suggests a role for GAL in the control of SRIF secretion and, in turn, in the regulation of GH release.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / ultrastructure*
  • Fluorescent Dyes
  • Galanin
  • Immunohistochemistry
  • Male
  • Microscopy, Immunoelectron
  • Nerve Fibers / ultrastructure
  • Neurons / cytology*
  • Neurons / ultrastructure
  • Neuropeptides / analysis*
  • Paraventricular Hypothalamic Nucleus / cytology*
  • Paraventricular Hypothalamic Nucleus / ultrastructure
  • Peptides / analysis*
  • Rats
  • Rats, Sprague-Dawley
  • Rats, Wistar
  • Somatostatin / analysis
  • Stilbamidines*


  • 2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt
  • Fluorescent Dyes
  • Neuropeptides
  • Peptides
  • Stilbamidines
  • Somatostatin
  • Galanin