Effect of body temperature on ventilatory control in the alligator.

Pulmonary ventilation and arterial blood acid-base balance were measured in six unanesthetized alligators, Alligator mississipiensis, at 15, 25, and 35 degree C. The animals exhibited pronounced ventilatory responses to hypercapnia at all temperatures studied. Arterial PCO2 increased and pH decreased with increases in body temperature during both normocapnia and hypercapnia. The fractional dissociation of imidazole (alpha Pr) remained constant with changes in body temperature during normocapnia, but increased with temperature during hypercapnia. Ventilatory sensitivity, defined as delta (VE/VO2/delta (alpha Pr), was independent of body temperature. We conclude that the control of breathing in the alligator is a physiological defense of alpha Pr and that ventilatory responses occur following nontemperature-induced changes in blood acid-base balance, which tend to return alpha Pr to a normal value.