AUTHOR=Fahlman Andreas , Bostrom Brian L., Dillon Kiran H., Jones David R.

TITLE=The Genetic Component of the Forced Diving Bradycardia Response in Mammals

JOURNAL=Frontiers in Physiology

VOLUME=2

YEAR=2011

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2011.00063

DOI=10.3389/fphys.2011.00063

ISSN=1664-042X

ABSTRACT=<p>We contrasted the forced diving bradycardia between two genetically similar (inbred) rat strains (Fischer and Buffalo), compared to that of outbred rats (Wistar). The animals were habituated to forced diving for 4 weeks. Each animal was then tested during one 40 s dive on each of 3 days. The heart rate (f<sub>H</sub>) was measured before, during, and after each dive. Fischer and Buffalo exhibited marked difference in dive bradycardia (Fischer: 120.9 ± 14.0 beats min<sup>−1</sup> vs. Buffalo: 92.8 ± 12.8 beats min<sup>−1</sup>, <italic>P</italic> &lt; 0.05). Outbred rats showed an intermediate response (103.0 ± 30.9 beats min<sup>−1</sup>) but their between-animal variability in mean dive f<sub>H</sub> and pre-diving resting f<sub>H</sub> were higher than the inbred strains (<italic>P</italic> &lt; 0.05), which showed no difference (<italic>P</italic> &gt; 0.05). The decreased variability in f<sub>H</sub> in inbred rats as compared with the outbred group indicates that reduced genetic variability minimizes variability of the diving bradycardia between individuals. Heritability within strains was assessed by the repeatability (<italic>R</italic>) index and was 0.93 ± 0.05 for the outbred, 0.84 ± 0.16 for Buffalo, and 0.80 ± 0.12 for Fischer rats for <italic>f</italic><sub>H</sub> during diving. Our results suggest that a portion of the mammalian diving bradycardia may be a heritable trait.</p>