Printed in Great Britain THE EFFECT OF INHALATIONAL ANAESTHETICS ON THE SWIMMING VELOCITY OF TETRAHYMENA PYRIFORMIS

The effect of 6 inhalational anaesthetics on speed of swimming (produced by ciliary move-ment) has been studied in Tetrahymena pyriformh. There was no evidence of stimulation at low dose levels and higher levels caused rapid, reversible, dose-dependent reduction in swimming velocity. The concentrations of anaesthetics which depressed motility by 50 % were of the same order as those required for anaesthesia in mammals, except in the case of cyclopropane, for which the required level was 4 times higher than the anaesthetic level. Correlation with lipid solubility was not as close as is the case for narcotic concentration. Oxygen consumption was reduced with increasing amounts of halothane in parallel with the reduction in swimming velocity. Halothane produced deciliation of Tetrahymena at about 10 times the anaesthetic dose for man; regrowth of cilia took place within 4 h of withdrawal of the drug. There were no changes in the ultrastructure of the cilia, basal bodies and associated microtubular systems at levels of halothane sufficient to stop cilial beat. At higher concentrations deciliation occurred immediately distal to the axosome and there was variable swelling of the mitochondria