Journal of Applied Physiology, Vol 58, Issue 6 1751-1754, Copyright © 1985 by American Physiological Society
Brain amino acid concentrations during diving and acid-base stress in turtles
B. M. Hitzig, M. P. Kneussl, V. Shih, R. D. Brandstetter and H. Kazemi
To assess the role of brain amino acid neurotransmitters in the breath hold
of diving animals, concentrations of free amino acids present in the brains
of turtles immediately after 2 h of apneic diving (at 20 degrees C) were
measured. Additionally, the same measurements were performed on four other
groups of animals subjected to 2 h of hypercapnia (8% CO2 in air), anoxia
(N2 breathing), anoxia plus hypercapnia (8% CO2-92% N2), or air breathing
(control). Significant changes in the concentrations of the inhibitory
amino acid neurotransmitters known to affect respiration
[gamma-aminobutyric acid (GABA) and taurine] were seen. GABA increased
significantly in those animals subjected to anoxia, whereas taurine
decreased significantly in the diving animals and increased significantly
in those subjected to anoxia plus hypercapnia. These results suggest that
the attenuated central ventilatory drive during diving in these animals may
be related to alterations in brain concentrations of GABA and taurine.
