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Diving Mice vs. Torpid Mice: A Comparison of Cardiovascular Regulation
Author(s) -
Hult Elissa M,
Bingaman Mark Jake,
Swoap Steven John
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.719.2
Subject(s) - bradycardia , heart rate , blood pressure , reflex , atropine , torpor , medicine , peripheral , autonomic nervous system , anesthesia , endocrinology , cardiology , thermoregulation
The diving response is a coordinated physiological response to submersion into water, and is used widely amongst mammals. The physiological response is composed of three primary effects: an immediate drop in heart rate, a reduced drive to breathe, and constriction of peripheral blood vessels. The diving response is important, not only because of its dramatic influence of the autonomic nervous system, but also because it inhibits or alters normal homeostatic reflexes such as the drive to breathe. We hypothesized that the cardiovascular effects and neural circuitry involved in the murine dive response are similar to those used in daily torpor. In this study, telemeters that measure arterial pressure and body temperature were implanted into female C57Bl/6J mice. These mice were trained to swim then voluntarily dive underwater for a distance of 60 cm over a 5 second period. After a recovery period, the same mice were calorically restricted to induce a bout of torpor. Just before the dive, the interbeat interval (IBI) was 87±3 msec and diastolic pressure was 100±8 mmHg. Diving caused a dramatic bradycardia immediately at the onset of each dive (IBI increased to 464±60 msec) and diastolic pressure dropped to 56±9 mmHg, that coincided with elevated peripheral resistance. Mice experienced a short bout (~5 sec) hypertension (diastolic pressure rose to 133±9 mmHg) upon emergence. The bradycardia and hypotension were dependent on vagal influence, as pre‐treatment with atropine blocked these responses. The same absolute changes to heart rate, blood pressure, and total peripheral resistance were observed in the torpid mouse, albeit at a different time scale. These data suggest that the drivers of the cardiovascular changes during a bout of torpor and during the diving response are likely shared. Support or Funding Information Supported by 1R15HL120072‐01A1 to SJS