title: CO(2)-induced c-Fos expression in hypothalamic vasopressin containing neurons.
abstract: Following exposure of anesthetized and unanesthetized rats to hypercapnic stress, arginine vasopressin (AVP)-containing neurons of the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei were examined for expression of the c-fos gene encoded protein (c-Fos). In addition, we determined whether AVP-containing PVN neurons activated by hypercapnia project to phrenic nuclei. In adult control rats, only scant c-Fos-like immunoreactive neurons were observed within the hypothalamic nuclei. A marked increase in c-Fos positive cells was induced after 2 h of breathing a gas mixture with elevated CO(2) (5% CO(2), 21% O(2) and 74% N(2), or 1 h following breathing of 12% CO(2,) 21% O(2,) and 67% N(2)). Colocalization studies of AVP and c-Fos protein revealed that in the PVN, 75% of AVP-containing cells expressed c-Fos immunoreactivity. c-Fos and AVP were coexpressed in 60% of SON neurons in anesthetized rats. In addition, retrograde labeling studies with cholera toxin b subunit (CTb) revealed that a subpopulation of PVN cells (15%) that project to phrenic nuclei are activated by hypercapnia, as indicated by c-Fos expression. These results indicate that (i) PVN and SON AVP-containing neurons are part of the neuronal networks that react to hypercapnic exposure; and (ii) a subset of CO(2) reactive PVN cells innervate phrenic nuclei.
authors.affiliation: Specialized Neuroscience Research Program, Department of Physiology and Biophysics, Howard University College of Medicine, 520 W St., NW, Washington, DC 20059, USA.
authors.forename: Prabha
authors.initials: P
authors.lastname: Kc
authors.forename: Musa A
authors.initials: MA
authors.lastname: Haxhiu
authors.forename: C Ovid
authors.initials: CO
authors.lastname: Trouth
authors.forename: Kannan V
authors.initials: KV
authors.lastname: Balan
authors.forename: Winston A
authors.initials: WA
authors.lastname: Anderson
authors.forename: Serdia O
authors.initials: SO
authors.lastname: Mack
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D006935:Hypercapnia / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism* / Q000503:physiopathology; D010791:Phrenic Nerve / Q000503:physiopathology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013495:Supraoptic Nucleus / Q000378:metabolism* / Q000473:pathology; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D001127:Arginine Vasopressin