Article Text

Degrees of aversion shown by rats and mice to different concentrations of inhalational anaesthetics
  1. M. C. Leach, BSc, MSc1,
  2. V. A. Bowell, BSc, MSc1,
  3. T. F. Allan, BA, MSc1 and
  4. D. B. Morton, BVSc, PhD, CBiol, FIBiol, MRCVS1
  1. 1 Centre for Biomedical Ethics, The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT


The distress associated with the induction of anaesthesia with halothane, isoflurane, enflurane and carbon dioxide was investigated in rats and mice by measuring the level of aversion they displayed on exposure to low, medium and high concentrations of these agents. The animals were exposed to each agent in a test chamber containing air or gas mixtures, which they were able to enter and leave at will, and the level of aversion was assessed in terms of the initial withdrawal and total dwelling times in the chamber. Comparisons between the anaesthetic and air-control treatments indicated that concentrations of the agents recommended for the rapid and efficient induction of anaesthesia were associated with some degree of aversion. Carbon dioxide was by far the most aversive gas for both rats and mice, with the least aversive being halothane for rats, and halothane and enflurane for mice. With all the anaesthetics, the level of aversion increased as the concentration increased.

Statistics from

Request permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.