Quantified EEG analysis monitoring in a novel model of general anaesthesia in rats

The aim of this research was to evaluate the safety and reliability of an anaesthetic mixture (Equitensine: pentobarbital, chloral hydrate, dihydroxypropane, ethanol) which, unlike other 'classic' anaesthetics, such as ketamine [The Electroencephalogram in Anaesthesia, Springer, Berlin, 1984], has been demonstrated not to induce alterations in the extracellular concentrations of cerebral excitatory amino acids. Quantified EEG analysis monitoring and behavioural observation were used to quantify the degree and the time course of the changes in cerebral electrical activity, analgesia and sedation induced, in rats, by the compound under investigation. Equitensine (0.33 ml/100 g), administered intraperitoneally, induced analgesia (monitored by the tail flick method) for 60-70 min and a pattern of behavioural sedation (loss of the righting reflex) lasting, on average, 130-150 min. The EEG monitoring revealed a pattern typical of burst suppression which lasted 15-20 min, followed by another, lasting 270-300 min, characterized by slow waves of high amplitude. The quantified EEG analysis demonstrated that the changes in cerebral electrical activity lasted longer than behavioural observation suggested. The compound under examination was found to be safe, reliable and non-invasive to administer and sustain in all the animals, and quantified EEG analysis proved to be a very sensitive method for highlighting the functional changes in the central nervous system.