Heart rate dynamics in a marsupial hibernator.
J Exp Biol
; 220(Pt 16): 2939-2946, 2017 08 15.
Article
in En
| MEDLINE
| ID: mdl-28576823
ABSTRACT
The eastern pygmy possum (Cercartetus nanus) is a small marsupial that can express spontaneous short bouts of torpor, as well as multi-day bouts of deep hibernation. To examine heart rate (fH) control at various stages of torpor in a marsupial hibernator, and to see whether fH variability differs from that of deep placental hibernators, we used radiotelemetry to measure ECG and body temperature (Tb) while measuring the rate of O2 consumption and ventilation. fH and O2 consumption rate during euthermia were at a minimum (321±34â
beatsâ
min-1, 0.705±0.048â
ml O2 g-1 h-1) at an ambient temperature (Ta) of 31°C. fH had an inverse linear relationship with Ta to a maximum of 630±19â
beatsâ
min-1 at a Ta of 20°C. During entry into torpor at a Ta of 20°C, fH slowed primarily as a result of episodic periods of cardiac activity where electrical activity of the heart occurred in groups of 3 or 4 heart beats. When Tb was stable at 24°C in these torpor bouts, the episodic nature of fH had disappeared (i.e. no asystoles) with a rate of 34±3â
beatsâ
min-1 For multi-day bouts of deep torpor, Ta was lowered to 6.6±0.8°C. During these deep bouts of torpor, Tb reached a minimum of 8.0±1.0°C, with a minimum fH of 8â
beatsâ
min-1 and a minimum O2 consumption rate of 0.029±0.07â
ml O2 g-1 h-1 Shivering bouts occurred in deep torpor about every 8â
min, during which ventilation occurred, and fH was elevated to 40â
beatsâ
min-1 The duration of the QRS complex increased from 12â
ms during euthermia to 69â
ms at a Tb of 8°C. These findings demonstrate the dynamic functioning range of fH to be about 600â
beatsâ
min-1 (â¼80-fold), one of the largest known ranges in mammals. Our study shows that despite a separation of â¼160 million years, the control and function of the cardiac system seems indistinguishable in marsupial and placental hibernating mammals.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Torpor
/
Heart Rate
/
Marsupialia
Limits:
Animals
Language:
En
Journal:
J Exp Biol
Year:
2017
Document type:
Article
Affiliation country:
United States
Publication country:
ENGLAND
/
ESCOCIA
/
GB
/
GREAT BRITAIN
/
INGLATERRA
/
REINO UNIDO
/
SCOTLAND
/
UK
/
UNITED KINGDOM