PSYCHOMOTOR PERFORMANCE DURING INITIAL-STAGE OF EXPOSURE TO HALOTHANE, ENFLURANE, ISOFLURANE AND SEVOFLURANE IN MICE

1. The dose-response relationship during the pre-anaesthetic and pre-e quilibrium state of four inhalation anaesthetics (halothane, enflurane , isoflurane and sevoflurane) on fixed-ratio schedule-controlled behav iour was studied in mice, 2, Animals exposed to halothane, enflurane a nd isoflurane showed a biphasic pattern (i,e, a significant incrementa l increase in psychomotor responses at low inspired concentrations (0. 1-0.4%) and decrements at greater concentrations) in a dose-dependent manner, Mean peak responses (per cent of control) were 132.3 (P<0.01 v s control), 124.0 (P<0.05) and 116.7% (P<0.05) at 0.1% halothane, 0.3% enflurane and 0.2% isoflurane, respectively, 3, Sevoflurane did not i ncrease schedule-controlled behavioural responses at any concentration , 4, The effect of subanaesthetic concentrations of inhalation anaesth etics on psychomotor performance can be evaluated as changes in the re sponse rate in schedule-controlled behaviour.