Comparison between EEG and observation of rabbit behaviour in evaluation of subarachnoid neurotoxicity of metrizamide.

The non-ionic contrast medium metrizamide (370 mg I/ml) was injected into the cisterna magna of rabbits at 2 dose levels (0.1 ml/kg and 0.5 ml/kg) to investigate whether visually evaluated EEG can detect neurotoxicity at a lower dose level than a method based on observation and ranking of signs of excitation and depression in animal behaviour. Half of the metrizamide injections were made without anaesthesia, whereas the remaining injections were made during a short alphadolon/alphaxolon anaesthesia. EEG and animal behaviour were followed for 24 h after the injection of metrizamide. At the low 'clinical' dose, EEG could not detect statistically significant neurotoxicity, neither in anaesthetized nor in non-anaesthetized rabbits. Observation of animal behaviour, however, could detect statistically significant signs of depression in animals that had been anaesthetized. At the high dose level, both methods could detect significantly more serious symptoms of neurotoxicity than at the low dose level.