Affiliation:
1. Department of Animal Morphology and Physiology, College of Agricultural and Veterinary Sciences, São Paulo State University, 14884-900, Jaboticabal, São Paulo, Brazil
2. National Institute of Science and Technology in Comparative Physiology (INCT Fisiologia Comparada), 14884-900, Jaboticabal, São Paulo, Brazil
Abstract
Anurans regulate short-term oscillations in blood pressure through changes in heart rate (fH), vascular resistance and lymph hearts frequency. Lung ventilation in anurans is linked to blood volume homeostasis by facilitating lymph return to the cardiovascular system. We hypothesized that the arterial baroreflex modulates pulmonary ventilation in the Cururu toad Rhinella schneideri, and that this relationship is temperature-dependent. Pharmacologically induced hypotension (sodium nitroprusside) and hypertension (phenylephrine) increased ventilation (25°C: 248.7±25.7; 35°C: 351.5±50.2 ml kg−1 min−1) and decreased ventilation (25°C: 9.0±6.6; 35°C: 50.7±15.6 ml kg−1 min−1), respectively, relative to control values from Ringer's injection (25°C: 78.1±17.0; 35°C: 137.7±15.5 ml kg−1 min−1). The sensitivity of the ventilatory response to blood pressure changes was higher during hypotension than hypertension (25°C: -97.6±17.1 vs. -23.6±6.0 breaths min−1 kPa−1; 35°C: -141.0±29.5 vs. -28.7±6.4 breaths min−1 kPa−1, respectively), while temperature had no effect on those sensitivities. Hyperoxia (30%; 25°C) diminished ventilation, but did not abolish the ventilatory response to hypotension, indicating a response independent of peripheral chemoreceptors. Although there are previous data showing increased fH baroreflex sensitivity from 15 to 30°C in this species, further increases in temperature (35°C) diminished fH baroreflex gain (40.5±5.62 vs. 21.6±4.64 % kPa−1). Therefore, besides a pulmonary ventilation role in matching O2 delivery to demand at higher temperatures in anurans, it also plays a role in blood pressure regulation, independent of temperature, possibly owing to an interaction between baroreflex and respiratory areas in the brain, as previously suggested for mammals.
Funder
Fundação de Amparo à Pesquisa do Estado de São Paulo
Publisher
The Company of Biologists
Subject
Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics
Cited by
13 articles.
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