PETERSEN, A.M.; GLEESON, T.T.; SCHOLNICK, D.A.: The influence of oxygen and adenosine on lizard thermoregulation
Anapyrexia is a regulated drop in internal body temperature (Tb) employed across taxa in a protective role against metabolic trauma. A clear mechanism responsible for anapyrexia has yet to be determined. This study examined the possibility that anapyrexia is initiated when low internal oxygen levels trigger the release of adenosine, a neural modulator known to influence thermoregulation. We measured selected Tb of Anolis sagrei in a thermal gradient under varied ambient oxygen conditions and following the administration of the adenosine receptor antagonist 8-cyclopentyltheophylline (CPT). Anapyrexia (about a 5oC decrease in average body temperature) was observed following exposure to hypoxia (<10% O2) as well as following exhaustive exercise (about a 3oC decrease in average body temperature), suggesting a role of oxygen availability on anapyrexia. When A. sagrei were run to exhaustion and recovered in hyperoxic (>95% O2) conditions, exercise induced anapyrexia was abolished. Administration of CPT similarly abolished both exercise and hypoxia induced anapyrexia. We suggest that when oxygen is limiting, a decrease in arterial oxygen may trigger the release of adenosine, thereby altering the thermoregulatory setpoint. These findings may be of particular importance as they suggest an ecologically pertinent mechanism for anapyrexia.
