title: A simple and novel method to monitor breathing and heart rate in awake and urethane-anesthetized newborn rodents.
abstract: Rodents are most useful models to study physiological and pathophysiological processes in early development, because they are born in a relatively immature state. However, only few techniques are available to monitor non-invasively heart frequency and respiratory rate in neonatal rodents without restraining or hindering access to the animal. Here we describe experimental procedures that allow monitoring of heart frequency by electrocardiography (ECG) and breathing rate with a piezoelectric transducer (PZT) element without hindering access to the animal. These techniques can be easily installed and are used in the present study in unrestrained awake and anesthetized neonatal C57/Bl6 mice and Wistar rats between postnatal day 0 and 7. In line with previous reports from awake rodents we demonstrate that heart rate in rats and mice increases during the first postnatal week. Respiratory frequency did not differ between both species, but heart rate was significantly higher in mice than in rats. Further our data indicate that urethane, an agent that is widely used for anesthesia, induces a hypoventilation in neonates whilst heart rate remains unaffected at a dose of 1 g per kg body weight. Of note, hypoventilation induced by urethane was not detected in rats at postnatal 0/1. To verify the detected hypoventilation we performed blood gas analyses. We detected a respiratory acidosis reflected by a lower pH and elevated level in CO2 tension (pCO2) in both species upon urethane treatment. Furthermore we found that metabolism of urethane is different in P0/1 mice and rats and between P0/1 and P6/7 in both species. Our findings underline the usefulness of monitoring basic cardio-respiratory parameters in neonates during anesthesia. In addition our study gives information on developmental changes in heart and breathing frequency in newborn mice and rats and the effects of urethane in both species during the first postnatal week.
authors: Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany. Zehendner@uni-mainz.de
authors: Christoph M
authors: CM
authors: Zehendner
authors: Heiko J
authors: HJ
authors: Luhmann
authors: Jenq-Wei
authors: JW
authors: Yang
mesh_terms: D000142:Acidosis, Respiratory / Q000097:blood / Q000139:chemically induced; D000758:Anesthesia; D018686:Anesthetics, Intravenous / Q000009:adverse effects*; D000818:Animals; D000831:Animals, Newborn; D001784:Blood Gas Analysis; D004562:Electrocardiography / Q000295:instrumentation* / Q000379:methods; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D007040:Hypoventilation / Q000097:blood / Q000139:chemically induced; D051379:Mice; D008810:Mice, Inbred C57BL; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration / Q000187:drug effects*; D014520:Urethane / Q000009:adverse effects*; D014851:Wakefulness / Q000502:physiology
chemical_list: D018686:Anesthetics, Intravenous; D014520:Urethane
references: Pediatr Res. 2005 Feb;57(2):299-304
references: 15585683
references: Respir Physiol. 1989 Dec;78(3):265-80
references: 2616924
references: Neuroimage. 2010 Jul 15;51(4):1367-77
references: 20350606
references: Respir Physiol. 1989 Oct;78(1):31-43
references: 2813986
references: J Appl Physiol (1985). 2005 Jan;98(1):365-70
references: 15591306
references: J Pharmacol Exp Ther. 2003 May;305(2):557-64
references: 12704224
references: J Neurosci. 2012 Jul 11;32(28):9511-6
references: 22787036
references: J Appl Physiol (1985). 2000 May;88(5):1907-14
references: 10797156
references: Physiol Rev. 2010 Apr;90(2):675-754
references: 20393196
references: Respir Physiol. 1979 Apr;36(3):375-89
references: 441588
references: J Physiol. 2012 Jul 15;590(14):3261-75
references: 22495584
references: Am J Physiol. 1986 Oct;251(4 Pt 2):H748-55
references: 3766752
references: J Neurosci. 2009 Jul 15;29(28):9011-25
references: 19605639
references: Anesth Analg. 1998 Oct;87(4):854-8
references: 9768782
references: Neuron. 2011 Jul 28;71(2):332-47
references: 21791291
references: PLoS One. 2012;7(12):e50752
references: 23251381
references: Br J Pharmacol. 1983 Jun;79(2):461-9
references: 6652337
references: Am J Physiol. 1977 Oct;233(4):H451-7
references: 910963
references: Nature. 2010 Nov 11;468(7321):232-43
references: 21068832
references: N Engl J Med. 2012 Jun 21;366(25):2409-19
references: 22716980
references: N Engl J Med. 1980 Aug 21;303(8):436-44
references: 6248784
references: Lab Anim. 1993 Jul;27(3):258-69
references: 8366672
references: Eur J Neurosci. 2008 Oct;28(7):1330-41
references: 18973560
references: Pflugers Arch. 1995 May;430(1):115-24
references: 7667071
references: J Appl Physiol (1985). 1997 Mar;82(3):874-81
references: 9074977
references: J Cereb Blood Flow Metab. 2012 Jul;32(7):1233-47
references: 22510601
references: Experientia. 1986 Mar 15;42(3):292-7
references: 3007197
references: Nutr Clin Pract. 2008 Apr-May;23(2):122-7
references: 18390779
references: Med Biol Eng Comput. 2006 May;44(5):353-62
references: 16937177
references: Neurosci Lett. 1997 Mar 7;224(1):13-6
references: 9132679
references: Ann Neurol. 2011 Oct;70(4):550-65
references: 21796662
references: J Neurosci. 2012 Aug 15;32(33):11259-70
references: 22895710
references: Am J Physiol Heart Circ Physiol. 2008 Apr;294(4):H1708-15
references: 18263713
references: Am J Physiol Regul Integr Comp Physiol. 2007 Nov;293(5):R2027-35
references: 17715184