title: Beta-endorphin-, adrenocorticotrophic hormone- and neuropeptide y-containing projection fibers from the arcuate hypothalamic nucleus make synaptic contacts on to nucleus preopticus medianus neurons projecting to the paraventricular hypothalamic nucleus in the rat.
abstract: The nucleus preopticus medianus is known to be situated in a key site in pathways regulating the paraventricular hypothalamic nucleus. To investigate the innervation pattern to nucleus preopticus medianus neurons by afferent fibers containing beta-endorphin, adrenocorticotrophic hormone and neuropeptide Y, a retrograde tracing method was combined with immunohistochemistry for these peptides in the rat. In the first experiment with injection of a retrograde tracer in the nucleus preopticus medianus, retrogradely labeled neurons were found in many regions throughout the brain. Among these, the arcuate hypothalamic nucleus contained a number of retrogradely labeled neurons showing immunoreactivity to the neuropeptides examined. About 20%, 20% and 40% of retrogradely labeled arcuate hypothalamic nucleus neurons showed beta-endorphin, adrenocorticotrophic hormone and neuropeptide Y immunoreactivity, respectively. About 18% and 57% of retrogradely labeled neurons in the nucleus tractus solitarius and ventrolateral medulla, respectively, were immunoreactive to neuropeptide Y. There were many more neuropeptide Y-immunoreactive projections to the nucleus preopticus medianus from the arcuate hypothalamic nucleus than those from the medulla. None of the retrogradely labeled neurons in the medulla showed immunoreactivity to beta-endorphin or adrenocorticotrophic hormone. In the second experiment with injection of a retrograde tracer in the paraventricular hypothalamic nucleus, electron microscopic observation revealed that retrogradely labeled neurons in the nucleus preopticus medianus were in synaptic contact with beta-endorphin-, adrenocorticotrophic hormone- and neuropeptide Y-immunoreactive axon terminals. The present finding indicates that nucleus preopticus medianus neurons projecting to the paraventricular hypothalamic nucleus are innervated by beta-endorphin-, adrenocorticotrophic hormone- and neuropeptide Y-containing arcuate hypothalamic nucleus neurons in addition to being innervated by neuropeptide Y-containing catecholaminergic medullary neurons which have been reported in our previous study.
authors.affiliation: Department of Anatomy, Saga Medical School, Nabeshima 5-1-1, 849-8501, Saga, Japan. kawanoh@post.saga-med.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Kawano
authors.forename: S
authors.initials: S
authors.lastname: Masuko
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000032:analysis; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology*; D008297:Male; D016253:Microscopy, Immunoelectron; D009412:Nerve Fibers / Q000737:chemistry* / Q000648:ultrastructure; D009434:Neural Pathways; D009478:Neuropeptide Y / Q000032:analysis; D009479:Neuropeptides / Q000032:analysis*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology*; D011301:Preoptic Area / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017552:Solitary Nucleus / Q000166:cytology; D013569:Synapses / Q000737:chemistry / Q000648:ultrastructure; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D001615:beta-Endorphin / Q000032:analysis
chemical_list: D009478:Neuropeptide Y; D009479:Neuropeptides; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone