Prostaglandins are important in thermoregulation of a reptile (Pogona vitticeps).
The effectiveness of behavioural thermoregulation in reptiles is amplified by cardiovascular responses, particularly by differential rates of heart beat in response to heating and cooling (heart-rate hysteresis). Heart-rate hysteresis is ecologically important in most lineages of ectothermic reptile, and we demonstrate that heart-rate hysteresis in the lizard Pogona vitticeps is mediated by prostaglandins. In a control treatment (administration of saline), heart rates during heating were significantly faster than during cooling at any given body temperature. When cyclooxygenase 1 and 2 enzymes were inhibited, heart rates during heating were not significantly different from those during cooling. Administration of agonists showed that thromboxane B(2) did not have a significant effect on heart rate, but prostacyclin and prostaglandin F(2alpha) caused a significant increase (3.5 and 13.6 beats min(-1), respectively) in heart rate compared with control treatments. We speculate that heart-rate hysteresis evolved as a thermoregulatory mechanism that may ultimately be controlled by neurally induced stimulation of nitric oxide production, or maybe via photolytically induced production of vitamin D.
Seebacher
Frank
F
School of Biological Sciences A08, University of Sydney, Sydney, NSW 2006, Australia. feebach@bio.usyd.edu.au
Franklin
Craig E
CE
D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D015237:Dinoprost / Q000494:pharmacology; D011464:Epoprostenol / Q000494:pharmacology; D006339:Heart Rate / Q000502:physiology; D007527:Isoenzymes / Q000378:metabolism; D008116:Lizards / Q000502:physiology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011453:Prostaglandins / Q000502:physiology*; D013929:Thromboxane B2 / Q000494:pharmacology
D007527:Isoenzymes; D011453:Prostaglandins; D013929:Thromboxane B2; D015237:Dinoprost; D011464:Epoprostenol; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases