title: Topographical distributions of endomorphinergic pathways from nucleus tractus solitarii to periaqueductal gray in the rat.
abstract: In the central nervous system (CNS), endomorphin 1 (EM1)- and endomorphin 2 (EM2)-containing neuronal cell bodies have been found in the nucleus tractus sollitarii (NTS) and the hypothalamus, and EMergic fibers and terminals are distributed widely in many regions of the CNS, including the periaqueductal gray (PAG). The aim of the present study was to examine whether EM-expressing neurons in the NTS of the rat send their axons to the PAG, and determine whether the EMergic pathway from the NTS to the PAG is topographic by using. Immunofluorescent staining for EM1 or EM2 combined with retrograde and anterograde tract-tracing methods. The results showed that after injecting tetramethyl rhodamine dextran-amine (TMR) into the ventrolateral or lateral column of the PAG, some EM1- or EM2-immunoreactive (IR) neurons in the NTS were retrogradely labeled with TMR, and the majority of the EM-IR/TMR double-labeled neurons were mainly distributed in the medial and commissural subnuclei of the NTS. Following injection of biotinylated dextran amine (BDA) into the medial or commissural subnucleus of the NTS, EM1-IR/BDA and EM2-IR/BDA double-labeled fibers and terminals were mainly distributed in the ventrolateral or lateral column of the PAG, respectively. The results indicate that EMergic pathway from the NTS to PAG is topographically organized, and suggest that EMs released from NTS to PAG projecting terminals may bind to mu-opioid receptor on the PAG neurons, and thereby contribute to various functions.
authors.affiliation: Department of Anatomy, Histology and Embryology, K. K. Leung Brain Research Centre, The Fourth Military Medical University, No. 17 West Changle Road, Xi'an, PR China.
authors.forename: Bo-Chang
authors.initials: BC
authors.lastname: Lv
authors.forename: Gen-Lin
authors.initials: GL
authors.lastname: Ji
authors.forename: Fu-Quan
authors.initials: FQ
authors.lastname: Huo
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Yun-Qing
authors.initials: YQ
authors.lastname: Li
mesh_terms: D000818:Animals; D005455:Fluorescent Antibody Technique; D008297:Male; D009434:Neural Pathways / Q000033:anatomy & histology* / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D010487:Periaqueductal Gray / Q000033:anatomy & histology* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017552:Solitary Nucleus / Q000033:anatomy & histology* / Q000378:metabolism
chemical_list: D009842:Oligopeptides; C105293:endomorphin 1; C105294:endomorphin 2