title: Galanin-immunoreactive axons innervate somatostatin-synthesizing neurons in the anterior periventricular nucleus of the rat.
abstract: 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.
authors.affiliation: Department of Anatomy, University Medical School, Pécs, Hungary.
authors.forename: Z
authors.initials: Z
authors.lastname: Liposits
authors.forename: I
authors.initials: I
authors.lastname: Merchenthaler
authors.forename: J J
authors.initials: JJ
authors.lastname: Reid
authors.forename: A
authors.initials: A
authors.lastname: Negro-Vilar
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D005456:Fluorescent Dyes; D019004:Galanin; D007150:Immunohistochemistry; D008297:Male; D016253:Microscopy, Immunoelectron; D009412:Nerve Fibers / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology* / Q000648:ultrastructure; D009479:Neuropeptides / Q000032:analysis*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology* / Q000648:ultrastructure; D010455:Peptides / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013004:Somatostatin / Q000032:analysis; D013266:Stilbamidines
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D009479:Neuropeptides; D010455:Peptides; D013266:Stilbamidines; D013004:Somatostatin; D019004:Galanin