title: Brainstem areas activated by intermittent apnea in awake unrestrained rats.
abstract: We investigated the role of the autonomic nervous system to cardiovascular responses to obstructive apnea in awake, unrestrained rats, and measured expression of Fos induced by apnea in the brainstem. We implanted a tracheal balloon contained in a rigid tube to allow the induction of apnea without inducing pain in the trachea. During bouts of 15s of apnea, heart rate fell from 371±8 to 161±11bpm (mean±SEM, n=15, p<0.01) and arterial pressure increased from 115±2 to 131±4mmHg (p<0.01). Bradycardia was due to parasympathetic activity because it was blocked by the muscarinic antagonist, methylatropine. The pressor response was due to vasoconstriction caused by sympathetic activation because it was blocked by the α1 antagonist, prazosin. Apnea induced Fos expression in several brainstem areas involved in cardiorespiratory control such as the nucleus of the solitary tract (NTS), ventrolateral medulla (VLM), and pons. Ligation of the carotid body artery reduced apnea-induced bradycardia, blocked heart rate responses to i.v. injection of cyanide, reduced Fos expression in the caudal NTS, and increased Fos expression in the rostral VLM. In conclusion, apnea activates neurons in regions that process signals from baroreceptors, chemoreceptors, pulmonary receptors, and regions responsible for autonomic and respiratory activity both in the presence and absence of carotid chemoreceptors.
authors: Department of Physiology, Federal University of São Paulo, 04023-062 São Paulo, SP, Brazil.
authors: C B
authors: CB
authors: Ferreira
authors: Department of Physiology, Federal University of São Paulo, 04023-062 São Paulo, SP, Brazil.
authors: G H
authors: GH
authors: Schoorlemmer
authors: Department of Physiology, Federal University of São Paulo, 04023-062 São Paulo, SP, Brazil.
authors: M V
authors: MV
authors: Rossi
authors: Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-000 São Paulo, SP, Brazil.
authors: A C
authors: AC
authors: Takakura
authors: Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, 05508-000 São Paulo, SP, Brazil.
authors: B F
authors: BF
authors: Barna
authors: Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, 05508-000 São Paulo, SP, Brazil.
authors: T S
authors: TS
authors: Moreira
authors: Department of Physiology, Federal University of São Paulo, 04023-062 São Paulo, SP, Brazil. Electronic address: sldcravo@unifesp.br.
authors: S L
authors: SL
authors: Cravo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001049:Apnea / Q000473:pathology* / Q000503:physiopathology*; D001286:Atropine Derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001933:Brain Stem / Q000187:drug effects / Q000503:physiopathology*; D002344:Carotid Body / Q000166:cytology; D002628:Chemoreceptor Cells / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010276:Parasympatholytics / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D014851:Wakefulness
chemical_list: D001286:Atropine Derivatives; D016761:Oncogene Proteins v-fos; D010276:Parasympatholytics; C006649:methylatropine; D014446:Tyrosine 3-Monooxygenase; D011224:Prazosin
keywords: arterial chemoreceptors; cFos immunoreactivity; hypoxia; medulla oblongata; obstructive apnea