QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Seebacher, F. Articles by Franklin, C. E. Search for Related Content PubMed PubMed Citation Articles by Seebacher, F. Articles by Franklin, C. E.

Control of heart rate during thermoregulation in the heliothermic lizard Pogona barbata: importance of cholinergic and adrenergic mechanisms

F. Seebacher^1,* and C. E. Franklin²

¹ School of Biological Sciences A08, The University of Sydney, NSW 2006, Australia and
² Department of Zoology and Entomology, The University of Queensland, Brisbane Qld 4072, Australia

View larger version (30K): [in a new window]   Fig. 1. Representative examples of heart rate (circles) and Tb (solid line) in Pogona barbata during heating and cooling. The first vertical line in each panel indicates when the infrared heat lamp was switched on, and the second vertical line indicates when the lamp was switched off. Lizards in the control treatment (A) were injected with saline, the muscarinic receptors were blocked during the atropine treatment (B) and cholinergic muscarinic and ß-adrenergic receptors were blocked by injection of atropine+sotalol (C). All pharmaceuticals were administered 2 h before experimentation.

View larger version (14K): [in a new window]   Fig. 2. Representative example of the cold red light control. Exposing lizards to cold red light had no effect on heart rate or Tb.

View larger version (13K): [in a new window]   Fig. 3. Heart rates of all lizards during heating (open circles) and cooling (filled circles). Heart rate hysteresis was apparent during the control treatment (Control) as well as during the cholinergic blockade (Atropine) and the combined cholinergic + ß-adrenergic blockade (Sotalol). Values are means ± S.E.M. (N=6).

View larger version (33K): [in a new window]   Fig. 4. The magnitude of the heart rate hysteresis during heating and cooling (expressed as the ratio of heart rate during heating:heart rate during cooling) was significantly different between lizards 1–6 and treatments (Atropine, cholinergic blockade; Control, control treatment; Sotalol, cholinergic + ß-adrenergic blockade). For details, see text. Values are means ± S.E.M.

View larger version (19K): [in a new window]   Fig. 5. Adrenergic (A) and cholinergic (B) tone on the heart during heating (filled circles) and cooling (open circles). Heart rate data were plotted against Tb during the heating and cooling trials so that the different body masses of the lizards were not confounding factors. Values are means ± S.E.M.

View larger version (20K): [in a new window]   Fig. 6. The tone on the heart of individual lizards (A–F) several minutes before and after the heat lamp was switched off at the end of the heating episode. The time at which the lamp was switched off is indicated by the vertical line at 0 min on the x-axis. Filled circles, adrenergic tone; open circles, cholinergic tone.

View larger version (26K): [in a new window]   Fig. 7. Lizards heated fastest when the cholinergic branch was blocked (Atropine) and slowest when both the cholinergic and ß-adrenergic branches were blocked (Sotalol). Values are means ± S.E.M.