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A simple and novel method to monitor breathing and heart rate in awake and urethane-anesthetized newborn rodents.

Zehendner CM, Luhmann HJ, Yang JW - PLoS ONE (2013)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany. Zehendner@uni-mainz.de

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.

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Impact of urethane anesthesia on cardio-respiratory parameters.In P0/1 mice RPM is significantly reduced by urethane but not in P0/1 rats (A). At P6/7 urethane resulted in a significant decrease of RPM in both species (B). The reduction of RPM was significantly higher in rats compared to mice (C). Urethane had no significant impact on heart rates in both species at all ages (D). Box and whisker plots (displaying 75th percentile, median and 25th percentile) are shown, whiskers indicate minimum and maximum values. *P<0.05, **P<0.01.
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pone-0062628-g003: Impact of urethane anesthesia on cardio-respiratory parameters.In P0/1 mice RPM is significantly reduced by urethane but not in P0/1 rats (A). At P6/7 urethane resulted in a significant decrease of RPM in both species (B). The reduction of RPM was significantly higher in rats compared to mice (C). Urethane had no significant impact on heart rates in both species at all ages (D). Box and whisker plots (displaying 75th percentile, median and 25th percentile) are shown, whiskers indicate minimum and maximum values. *P<0.05, **P<0.01.

Mentions: Urethane is widely used to induce anesthesia [13]. Therefore we elucidated its effect on heart and respiratory rate at a dose of 1 g per kg body weight 30 to 60 minutes after its administration. This dosage is commonly used for anesthetic purposes in rodents [14]. At P0/1 we observed a significant reduction of RPM in urethane treated mice compared with the awake state (mice P0/1 awake: 140±38 RPM vs. mice P0/1 urethane: 108±33 RPM, n = 6 animals, P<0.05, Figure 3A). RPM in P0/1 rats was not significantly reduced upon urethane treatment (rats P0/1 awake: 144±39 RPM vs. rats P0/1 urethane: 120±38 RPM, n = 7 animals, P>0.05, Figure 3A). At P6/7 urethane reduced RPM in both species (rats P6/7 awake: 232±30 RPM vs. rats P6/7 urethane: 155±9 RPM, n = 5 animals, P<0.01; mice P6/7 awake: 270±26 RPM vs. mice P6/7 urethane: 230±39 RPM, n = 5 animals, P<0.01, Figure 3B). To determine if the urethane induced depression of breathing was more severe in one of the two species we evaluated the relative reduction of RPM in both groups at P6/7. We found that breathing frequency of P6/7 rats was significantly more diminished by urethane than in P6/7 mice (rats P6/7 urethane: 33±13% vs. mice P6/7 urethane: 15±6%, n = 5 animals, P<0.05, Figure 3C). Contrary to our findings on the effect of urethane on breathing, heart rate did not change significantly upon urethane administration (rats P0/1 awake: 276±74 BPM vs. rats P0/1 urethane: 281±65 BPM, n = 7 animals; rats P6/7 awake: 423±9 BPM vs. rats P6/7 urethane: 387±77 BPM, n = 5 animals; mice P0/1 awake: 379±67 BPM vs. mice P0/1 urethane: 381±99 BPM, n = 6 animals; mice P6/7 awake: 582±45 BPM vs. mice P6/7 urethane: 535±53 BPM, n = 5 animals, P>0.05 in all groups, Figure 3D).


A simple and novel method to monitor breathing and heart rate in awake and urethane-anesthetized newborn rodents.

Zehendner CM, Luhmann HJ, Yang JW - PLoS ONE (2013)

Impact of urethane anesthesia on cardio-respiratory parameters.In P0/1 mice RPM is significantly reduced by urethane but not in P0/1 rats (A). At P6/7 urethane resulted in a significant decrease of RPM in both species (B). The reduction of RPM was significantly higher in rats compared to mice (C). Urethane had no significant impact on heart rates in both species at all ages (D). Box and whisker plots (displaying 75th percentile, median and 25th percentile) are shown, whiskers indicate minimum and maximum values. *P<0.05, **P<0.01.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3643944&req=5

pone-0062628-g003: Impact of urethane anesthesia on cardio-respiratory parameters.In P0/1 mice RPM is significantly reduced by urethane but not in P0/1 rats (A). At P6/7 urethane resulted in a significant decrease of RPM in both species (B). The reduction of RPM was significantly higher in rats compared to mice (C). Urethane had no significant impact on heart rates in both species at all ages (D). Box and whisker plots (displaying 75th percentile, median and 25th percentile) are shown, whiskers indicate minimum and maximum values. *P<0.05, **P<0.01.
Mentions: Urethane is widely used to induce anesthesia [13]. Therefore we elucidated its effect on heart and respiratory rate at a dose of 1 g per kg body weight 30 to 60 minutes after its administration. This dosage is commonly used for anesthetic purposes in rodents [14]. At P0/1 we observed a significant reduction of RPM in urethane treated mice compared with the awake state (mice P0/1 awake: 140±38 RPM vs. mice P0/1 urethane: 108±33 RPM, n = 6 animals, P<0.05, Figure 3A). RPM in P0/1 rats was not significantly reduced upon urethane treatment (rats P0/1 awake: 144±39 RPM vs. rats P0/1 urethane: 120±38 RPM, n = 7 animals, P>0.05, Figure 3A). At P6/7 urethane reduced RPM in both species (rats P6/7 awake: 232±30 RPM vs. rats P6/7 urethane: 155±9 RPM, n = 5 animals, P<0.01; mice P6/7 awake: 270±26 RPM vs. mice P6/7 urethane: 230±39 RPM, n = 5 animals, P<0.01, Figure 3B). To determine if the urethane induced depression of breathing was more severe in one of the two species we evaluated the relative reduction of RPM in both groups at P6/7. We found that breathing frequency of P6/7 rats was significantly more diminished by urethane than in P6/7 mice (rats P6/7 urethane: 33±13% vs. mice P6/7 urethane: 15±6%, n = 5 animals, P<0.05, Figure 3C). Contrary to our findings on the effect of urethane on breathing, heart rate did not change significantly upon urethane administration (rats P0/1 awake: 276±74 BPM vs. rats P0/1 urethane: 281±65 BPM, n = 7 animals; rats P6/7 awake: 423±9 BPM vs. rats P6/7 urethane: 387±77 BPM, n = 5 animals; mice P0/1 awake: 379±67 BPM vs. mice P0/1 urethane: 381±99 BPM, n = 6 animals; mice P6/7 awake: 582±45 BPM vs. mice P6/7 urethane: 535±53 BPM, n = 5 animals, P>0.05 in all groups, Figure 3D).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany. Zehendner@uni-mainz.de

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.

Show MeSH
Related in: MedlinePlus