Acute effects of ethanol on spontaneous and auditory evoked electrical activity in cat brain

Effects of ethanol were studied in twenty conscious, freely moving adult cats, each with indwelling electrodes located in three cortical and four subcortical loci. Each animal was studied at different levels of arousal and activity without drug, and then during and after intravenous infusions of the same total dose of ethanol (1 g/kg) given as 10, 20 and 30% (v/v) solutions at a constant rate of 3 ml/min. Blood alcohol curves were obtained during similar infusions. Spontaneous electrical activity showed initial increase of frequency and amplitude in the cortical leads, and decrease in the midbrain reticular formation (MRF), with all alcohol solutions. However, with the higher concentrations this soon passed over to progressive decrease in both frequency and amplitude in all leads except the hippocampus, as marked behavioural depression appeared. The 10% solution did not produce this phase, the animals returning quickly to their pre-alcohol state. Auditory evoked responses showed marked decrease in amplitude and fragmentation of the peaks during infusion of 20 and 30% ethanol solutions, but increased amplitude with the 10% solution. Changes were more marked in the MRF than in auditory cortex. Both spontaneous and evoked activity changes were indicative of rapid development of acute tolerance to ethanol. The findings differed markedly with the different solutions, despite the same total dose; this may explain divergent observations by various investigators in the past. Les effets de l'Ethanol ont été étudiés sur 20 chats adultes conscients et libres de leurs mouvements, portant tous des électrodes implantées localisées à 3 points corticaux et 4 points souscorticaux. Chaque animal est étudié à différents niveaux d'éveil et d'activité sans drogue, puis pendant et après instillation intra-veineuse de la même dose totale d'Ethanol (1 g/kg) donnée en solution de 10, 20 et 30% à une vitesse constante de 3 ml/min. Les courbes d'alcool sanguin sont obtenues au cours d'instillations similaires. L'activité électrique spontanée montre une augmentation initiale de la fréquence et de l'amplitude des dérivations corticales et la diminution dans la formation réticulaire du tronc cérébral médian, pour toutes les solutions alcoolisées. Cependant avec les concentrations supériures, ceci se transforme rapidement en une diminution progressive de la fréquence et de l'amplitude dans toutes les dérivations exceptées l'hippocampe, au moment où apparait une dépression marquée du com