title: Synaptic contact between median preoptic neurons and subfornical organ neurons projecting to the paraventricular hypothalamic nucleus.
abstract: It is known that the median preoptic nucleus (POMe) sends dense projections to the subfornical organ (SFO). However, the functional significance of these projections have not been well discussed. In this electron microscopic study, we investigated the presence of synapses between POMe-derived axon terminals and SFO neurons that project to the paraventricular hypothalamic nucleus (PVN). After injection of a retrograde tracer, wheat germ agglutinin-conjugated horseradish peroxidase-colloidal gold complex, into the PVN, many labeled neurons were found in the SFO. In contrast, after injection of an anterograde tracer, biotinylated dextran amine, in the POMe, abundant labeled axon varicosities were observed in the SFO. Using electron microscopy, synapses were identified between retrogradely labeled dendrites and cell bodies, and anterogradely labeled axon terminals, indicating that POMe neurons innervate SFO neurons projecting to the PVN. The possibility that POMe neurons play multiple roles in the neuronal circuit responsible for vasopressin release and/or cardiovascular regulation is also discussed.
authors.affiliation: Faculty of Medicine, Institute of Nursing, Morphology and Function for Nursing, Saga University, Nabeshima 5-1-1, Saga, 849-8501, Japan. kawanoh@cc.saga-u.ac.jp.
authors.forename: Hitoshi
authors.identifier: http://orcid.org/0000-0003-3528-1431
authors.initials: H
authors.lastname: Kawano
mesh_terms: D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D003911:Dextrans / Q000378:metabolism; D017979:Gold Colloid / Q000378:metabolism; D008297:Male; D008845:Microinjections; D016253:Microscopy, Immunoelectron; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology*; D011301:Preoptic Area / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013356:Subfornical Organ / Q000166:cytology*; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D014909:Wheat Germ Agglutinins / Q000378:metabolism
chemical_list: D003911:Dextrans; D017979:Gold Colloid; D014909:Wheat Germ Agglutinins; C076397:biotinylated dextran amine; C051777:wheat germ agglutinin-gold; D001710:Biotin
keywords: Anterograde tracing; Electron microscopy; Retrograde tracing; Synapse