Inhibition of adrenal medullary catecholamine secretion by enflurane: I. Investigations in vivo.

The effects of enflurane anesthesia on adrenal medullary catecholamine secretion and on the pressor effect of splanchnic-nerve stimulation were studied in cats given pentobarbital for basal anesthesia. Inhalation of enflurane, 1.2 and 2.2 per cent, caused dose-related inhibition of both spontaneous catecholamine release and secretion evoked by splanchnic-nerve stimulation. During inhalation of 2.2 per cent enflurane spontaneous release of epinephrine was decreased to 19 and 25 per cent, respectively, of the initial values, and the stimulated release was decreased to 30 and 15 per cent, respectively. Enflurane also inhibited the pressor effect of splanchnic-nerve stimulation, whereas that of norepinephrine was not changed significantly. These results are similar to those previously obtained with halothane and methoxyflurane. It is concluded that the decrease in catecholamine secretion caused by enflurane is in part due to a direct effect on the chromaffin cell, namely to an inhibition of the secretion-stimulating effect of acetylcholine released from splanchnic nerves.