title: Cytoarchitecture and CO(2) sensitivity of Phox2b-positive Parafacial neurons in the newborn rat medulla.
abstract: Preinspiratory (Pre-I) neurons in the parafacial respiratory group (pFRG) compose one of the respiratory rhythm generators in the medulla of the newborn rat. It has been shown that a subgroup of pFRG/Pre-I neurons could also work as central chemoreceptor neurons, because the CO(2) sensitivity of these Pre-I neurons was preserved even after blockade of Na(+) channels and Ca(2+) channels, and the membrane depolarization induced by hypercapnic stimulation was mainly because of the closing of K(+) channels. These neurons, some of which were identified to be glutamatergic, express the transcription factor Phox2b. Phox2b expression was one of the most noticeable characteristics of pFRG/Pre-I neurons. We also found that Phox2b-expressing neurons in the parafacial region of the rostral ventral medulla tended to assemble around capillary blood vessels. In contrast, another subclass of the pFRG/Pre-I neurons was Phox2b-negative and CO(2)-insensitive. Some of these neurons were identified to be glycinergic or GABAergic. Thus, Phox2b expression is a key genetic marker that can be used to more clearly establish the cell architecture of the pFRG, which consists of heterogeneous neuronal subtypes. In this chapter, we elaborate on the CO(2) sensitivity of Phox2b-positive/negative parafacial neurons and the cytoarchitecture in the newborn rat medulla, and discuss ionic mechanisms of CO(2) responsiveness.
authors.affiliation: Department of Physiology, Showa University School of Medicine, Shinagawa-ku, Tokyo, Japan. Electronic address: oni@med.showa-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Onimaru
authors.affiliation: Division of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: Department of Physiology, Showa University School of Medicine, Shinagawa-ku, Tokyo, Japan.
authors.forename: Tani
authors.initials: T
authors.lastname: Mariho
authors.affiliation: Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kawakami
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002245:Carbon Dioxide / Q000378:metabolism; D002628:Chemoreceptor Cells / Q000166:cytology* / Q000502:physiology*; D018398:Homeodomain Proteins / Q000096:biosynthesis; D009474:Neurons / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D012125:Respiratory Center / Q000166:cytology* / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis
chemical_list: D018398:Homeodomain Proteins; C109220:NBPhox protein; D014157:Transcription Factors; D002245:Carbon Dioxide
keywords: GAD; Glyt2; Phox2b; TASK; central chemoreceptor; parafacial respiratory group; respiratory rhythm; rostral ventrolateral medulla