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Temperature effect on cardiorespiratory responses and autonomic modulation of heart rate in premetamorphic bullfrog tadpoles, Lithobates catesbeianus
Author(s) -
Longhini Leonardo S,
Zena Lucas A,
Silva Glauber SF,
Bícego Kênia C,
Gargaglioni Luciane H
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.719.8
Subject(s) - bullfrog , heart rate , cardiorespiratory fitness , medicine , endocrinology , vagal tone , atropine , adrenergic , vagus nerve , amphibian , autonomic nervous system , biology , chemistry , blood pressure , stimulation , receptor , ecology
American bullfrog tadpoles exhibit an inhibitory vagal tone in the heart, while in adults; vagal tone becomes considerably reduced and virtually independent of temperature. Temperature effects on cardiac autonomic tonus in amphibian's larval stages have never been investigated. Therefore, we evaluated the effect of different temperatures (15, 25, and 30°C) on the cardiorespiratory responses and cardiac autonomic tonus of premetamorphic bullfrog tadpoles, Lithobates castebeianus . A non‐invasive method for measuring ECG and breathing frequency ( f R ) was developed. For pharmacological study, intraperitoneal injections of ringer solution (control), atropine (cholinergic muscarinic antagonist), and sotalol (β‐adrenergic antagonist) were performed. Ringer injections did not affect heart rate ( f H ) and f R across temperatures. Cardiorespiratory parameters were significantly augmented by temperature [ f H (beats.min −1 ): 15°C: 24.5±1.0; 25°C: 54.5±2.0; 30°C: 75.8±2.8 and f R (breaths.min −1 ) : 15°C: 30.3±1.1; 25°C: 73.1±4.0; 30°C: 100.6±3.7]. A predominant vagal tone was observed at 15 (32.0±3.2%) and 25°C (27.2±6.7%) relative to the adrenergic tone. At 30°C, adrenergic tone increases relative to the lower temperature. This study provides a suitable non‐invasive method for studying cardiorespiratory function (ECG and electromyography of the buccal floor) in tadpoles. Furthermore, cholinergic and adrenergic tone seems to be independent of temperature for the thermal interval between 15 and 25°C, while animals' exposure to 30°C is followed by a significant increase in adrenergic tone that may reflect cardiovascular adjustment in order to match oxygen delivery to demand. Support or Funding Information FAPESP and CNPq