The effect of hypothalamic thermal stimulation on respiration in the turtle

Cumulative Oxygen Consumption (VO2) and Oxygen Consumption per Unit Time were measured for fresh water turtles (Pseudemys scripta elegans) as hypothalamic stimulation was applied. Stimulation was provided by means of a thermode at 9-2o C (cold), 27o C (sham), and 55-60 degrees C (HOT). A statistically significant increase in mean cumulative oxygen consumption was noted for hot stimulation as compared to control value. A less dramatic but significant decrease in mean cumulative oxygen consumption was noted for cold stimulation. Both the increase and decrease, for hot and cold application, respectively, were proportional to the temperature of the thermode. Mean cumulative oxygen consumption per unit time did not show any corresponding statistically significant increase or decrease for hot or cold stimulation, respectively. Application of thermode at room temperature (sham) produced no significant change in respiration. This study indicates that reptiles have evolved a neural input mechanism sensitive to temperature change before mammalian and avian endothermy had developed.