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Evidence of baroreflex in tegu lizards
Author(s) -
Bicego Kenia Cardoso,
Dantonio Valter,
Toledo Ana Gabriela,
Gargaglioni Luciane Helena
Publication year - 2010
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.24.1_supplement.lb615
Subject(s) - baroreflex , sodium nitroprusside , blood pressure , heart rate , phenylephrine , biology , zoology , anesthesia , medicine , endocrinology , nitric oxide
Tegu lizards have hearts with a ventricule anatomically and functionally undivided. Thus, blood pressures are equal in the systemic and pulmonary circulations leading to a blood flow distribution dependent on their relative vascular resistances. There is evidence for the baroreflex control in some species of reptiles, but no conclusive data exist for tegus. The present study aimed to verify the presence of a functional baroreflex in the tegu lizard, Tupinambis merianae , during winter (hibernation; June‐August) and spring (activity; October‐December). Arterial blood pressure (ABP) and heart rate (HR) were determined after systemic injections of sodium nitroprusside (SNP; 2.5, 5, 10, 25 μg/kg) and phenylephrine (PE; 5, 10, 25, 50 μg/kg). Experiments were conducted at 24–27oC in both seasons to eliminate temperature effect on ABP and HR. Basal ABP and HR were, respectively: 35.5 ± 1.3 mmHg and 10 ± 1.5 bpm (winter) and 34.7 ± 1.4 mmHg and 13.3 ± 0.7 bpm (spring). All doses of SNP caused significant increases in ABP with respective decreases in HR in both seasons. PE induced a dose dependent increase in ABP, a response that was more prominent during spring, but did not affect HR regardless season. The results indicate the presence of a hypotensive baroreflex in T. merianae during winter and spring. The lack of reflex response of HR to the PE injections remains to be clarified. Supported by FAPESP, CNPq. INCT Fisiologia Comparada.