Journal of Applied Physiology

Catecholaminergic modulation of respiratory rhythm in an in vitro turtle brain stem preparation

Rebecca A. Johnson, Stephen M. Johnson, Gordon S. Mitchell


An in vitro brain stem preparation from adult turtles was used to determine effects of dopamine (DA) and norepinephrine (NE) on the pattern of respiratory motor output recorded from hypoglossal nerve roots (XII). Bath-applied DA (10–200 μM) increased the frequency of respiratory bursts (peaks) from 0.9 ± 0.2 to 2.4 ± 0.3 (SE) peaks/min, resulting in a 99 ± 9% increase in neural minute activity.R[+]-SCH-23390 (10 μM, D1 antagonist) and eticlopride (20 μM, D2 antagonist) attenuated the DA-mediated increase in peak frequency by 52 and 59%, respectively. On the other hand, the DA-receptor agonists apomorphine (D1, D2), quinelorane (D2), and SKF-38393 (D1) had no effect on peak frequency. Prazosin, an α1-adrenergic antagonist (250 nM) abolished the DA-mediated frequency increase. Although NE (10–200 μM) and phenylephrine (10–200 μM, α1-adrenergic agonist) increased peak frequency from 0.5 ± 0.1 to 1.2 ± 0.3 peaks/min and from 0.6 ± 0.1 to 1.0 ± 0.2 peaks/min, respectively, these effects were not as large as that with DA alone. The data suggest that both dopaminergic and adrenergic receptor activation in the brain stem increase respiratory frequency in turtles, but the DA receptor-mediated increase is dependent on coactivation of α1-adrenergic receptors.

  • respiratory control
  • reptile
  • dopamine
  • brain stem
  • norepinephrine


  • Address for reprint requests: R. A. Johnson, Dept. of Comparative Biosciences, School of Veterinary Medicine, Univ. of Wisconsin, 2015 Linden Drive West, Madison, WI 53706.

  • This work was supported by National Heart, Lung, and Blood Institute Grants HL-53319 and HL-36780. S. M. Johnson is a fellow of the Parker B. Francis Foundation in Pulmonary Research.

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