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Autonomic control of heart rate during forced activity and digestion in the snake Boa constrictor

Tobias Wang^1,2,3,*, E. W. Taylor^1,2, Denis Andrade¹ and Augusto S. Abe¹

¹ Department of Zoology, UNESP Rio Claro, Brazil,
² School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK and
³ Institute of Biology, Aarhus University, 8000 Aarhus C, Denmark

View larger version (18K): [in a new window]   Fig. 1. Original recordings of heart rate (fH) and systemic blood pressure (Psys) in two different snakes used for the studies of enforced activity (A) and the effects of digestion (B).

View larger version (16K): [in a new window]   Fig. 2. Systemic blood pressure (Psys) for Boa constrictor during resting undisturbed conditions (A), during forced activity (B) and during digestion (C). The figure depicts the untreated control condition (N=8) and the values obtained following autonomic blockade with the ß-adrenergic antagonist propranolol (3 mg kg–1) and the muscarinic cholinoceptor antagonist atropine (3 mg kg–1; N=4 for both) and following double autonomic blockade (N=8). The fasting blood pressure is also shown for the snakes studied during digestion (C). Values are means + S.E.M. An asterisk indicates a significant difference from the resting value.

View larger version (16K): [in a new window]   Fig. 3. Heart rate for Boa constrictor during resting and undisturbed conditions (A), during forced activity (B) and during digestion (C). The figure depicts the untreated control condition (N=8) and the values obtained following autonomic blockade with the ß-adrenergic antagonist propranolol (3 mg kg–1) and the muscarinic cholinoceptor antagonist atropine (3 mg kg–1; N=4 for both) and following double autonomic blockade (N=8). The fasting heart rate is also shown for the snakes studied during digestion (C). Values are means + S.E.M. An asterisk indicates a significant difference from the value of untreated and resting animals; a double dagger indicates a significant difference from the value of double-blocked and resting animals.

View larger version (11K): [in a new window]   Fig. 4. The calculated autonomic tones on the heart for Boa constrictor during undisturbed rest (A), during forced activity (B) and during digestion (C). Values are means + S.E.M. An asterisk indicates a significant difference from the value of untreated and resting animals; a double dagger indicates a significant difference between forced activity and digestion. Cho, cholinergic; Adr, adrenergic.

View larger version (13K): [in a new window]   Fig. 5. Relationship between the heart rate of fasting, undisturbed and resting snakes and the cholinergic tone (filled circles) and the adrenergic tone (open squares) in Boa constrictor. The lines are linear regressions (cholinergic tone, r2=0.663, P=0.01; adrenergic tone, r2<0.01, P=0.94).