The Effects of Cyclopropane, Halothane and Diethyl Ether on the Cerebral Metabolism of Serotonin in the Rat

The effects of cyclopropane, halothane and diethyl ether on cerebral levels of serotonin (5-HT) and its principal metabolite, 5-hydroxyindoleacetic acid (5-HIAA), were studied in rats. The turnover rate of cerebral 5-HT was measured, using steady-state kinetics after inhibition of monoamine oxidase or blockade of acid transport, during exposure to 15 per cent cyclopropane, 0.75 per cent halothane, or 3 per cent diethyl ether. Cerebral content of 5-HT increased slightly (14 per cent) during cyclopropane anesthesia; decreased (17 per cent) with halothane; and did not change with diethyl ether. 5-HIAA levels increased with all three anesthetics, especially with diethyl ether (100 per cent), probably due to a decrease in its rate of removal from the brain. The turnover rate of brain 5-HT remained unchanged with cyclopropane and halothane, but increased considerably with diethyl ether.