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Vol. 84, Issue 2, 649-660, February 1998
Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, Wisconsin 53706
Johnson, Stephen M., Rebecca A. Johnson, and Gordon S. Mitchell. Hypoxia, temperature, and
pH/CO2 effects on respiratory discharge from a turtle brain stem preparation. J. Appl. Physiol. 84(2): 649-660, 1998.
An in vitro
brain stem preparation from adult turtles (Chrysemys
picta) was used to examine the effects of anoxia and
increased temperature and pH/CO2
on respiration-related motor output. At pH ~7.45, hypoglossal (XII)
nerve roots produced patterns of rhythmic bursts (peaks) of discharge
(0.74 ± 0.07 peaks/min, 10.0 ± 0.6 s duration) that were
quantitatively similar to literature reports of respiratory activity in
conscious, vagotomized turtles. Respiratory discharge was stable for 6 h at 22°C; at 32°C, peak amplitude and frequency progressively
and reversibly decreased with time. Two hours of hypoxia had no effect
on respiratory discharge. Acutely increasing bath temperature from 22 to 32°C decreased episode and peak duration and increased peak
frequency. Changes in pH/CO2
increased peak frequency from zero at pH 8.00-8.10 to maxima of
0.81 ± 0.01 and 1.44 ± 0.02 peaks/min at 22°C (pH 7.32) and
32°C (pH 7.46), respectively;
pH/CO2 sensitivity was similar at
both temperatures. We conclude that
1) insensitivity to hypoxia
indicates that rhythmic discharge does not reflect gasping behavior,
2) increased temperature alters
respiratory discharge, and 3)
central pH/CO2 sensitivity is
unaffected by temperature in this preparation (i.e.,
Q10 ~1.0).
chelonia; medulla; breathing; reptile; chemosensitivity
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  S. M. Johnson and R. J. Creighton Spinal cord injury-induced changes in breathing are not due to supraspinal plasticity in turtles (Pseudemys scripta) Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2005; 289(6): R1550 - R1561. [Abstract] [Full Text] [PDF]
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 R. E. Winmill, A. K. Chen, and M. S. Hedrick Development of the respiratory response to hypoxia in the isolated brainstem of the bullfrog Rana catesbeiana J. Exp. Biol., January 15, 2005; 208(2): 213 - 222. [Abstract] [Full Text] [PDF]
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 B. E. Taylor, M. B. Harris, E. L. Coates, M. J. Gdovin, and J. C. Leiter Central CO2 chemoreception in developing bullfrogs: anomalous response to acetazolamide J Appl Physiol, March 1, 2003; 94(3): 1204 - 1212. [Abstract] [Full Text] [PDF]
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M. B. Harris, R. J. A. Wilson, K. Vasilakos, B. E. Taylor, and J. E. Remmers Central respiratory activity of the tadpole in vitro brain stem is modulated diversely by nitric oxide Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2002; 283(2): R417 - R428. [Abstract] [Full Text] [PDF]
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S. M. Johnson, J. E. R. Wilkerson, D. R. Henderson, M. R. Wenninger, and G. S. Mitchell Serotonin elicits long-lasting enhancement of rhythmic respiratory activity in turtle brain stems in vitro J Appl Physiol, December 1, 2001; 91(6): 2703 - 2712. [Abstract] [Full Text] [PDF]
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R. Wilson, M. Harris, J. Remmers, and S. Perry Evolution of air-breathing and central CO(2)/H(+) respiratory chemosensitivity: new insights from an old fish? J. Exp. Biol., January 11, 2000; 203(22): 3505 - 3512. [Abstract] [PDF]
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R. A. Johnson, S. M. Johnson, and G. S. Mitchell Catecholaminergic modulation of respiratory rhythm in an in vitro turtle brain stem preparation J Appl Physiol, July 1, 1998; 85(1): 105 - 114. [Abstract] [Full Text] [PDF]
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