EFFECTS OF ANESTHESIA WITH HALOTHANE AND METHOXYFLURANE ON PLASMA-CORTICOSTERONE CONCENTRATION IN RATS AT REST AND AFTER EXERCISE

To determine whether halothane and methoxyflurane are suitable anesthe tics for cardiac puncture in studies of plasma corticosterone concentr ation in rats, four experiments were done. Blood samples were taken im mediately after rats became anesthetized with halothane or methoxyflur ane. Decapitation without anesthesia was used to determine baseline co rticosterone concentration. Another group of rats was anesthetized wit h ether as a positive control (known to stimulate corticosterone secre tion). Corticosterone values in halothane- and methoxyflurane-treated rats were not significantly different from those measured after decapi tation. Corticosterone concentration in halothane-treated rats was sig nificantly lower than that in either methoxyflurane- or ether-treated rats. Cardiac puncture was done after 3 min of exposure to each of the three anesthetics. The results indicated that there were no differenc es in corticosterone values among the three anesthetics, suggesting th at corticosterone concentration was lower immediately after halothane was used as the anesthetic, because halothane induced anesthesia in le ss time than that required for activation of adrenocortical secretion. To determine whether there was a difference among anesthetics in stim ulating corticosterone secretion when anesthesia was maintained for a period before blood sample collection, cardiac puncture was done after 15 min of exposure to each of the three anesthetics. Corticosterone v alues were similar, suggesting that any of the three anesthetics was a cceptable in this situation. To determine whether halothane or methoxy flurane affected exercise-induced increases in corticosterone values, exercise-trained rats were run for 30 min; then blood samples were col lected by cardiac puncture immediately after induction of anesthesia w ith halothane, methoxyflurane, or ether, or after decapitation without anesthesia. Corticosterone values were not different among the three anesthetics or decapitation.