RAPID HABITUATION OF AUDITORY RESPONSES OF LOCUS-COERULEUS CELLS IN ANESTHETIZED AND AWAKE RATS

THE auditory response of locus coeruleus (LC) neurones evoked by novel tones was investigated in anaesthetized and awake rats. Recording the single unit activity of LC neurones, responses to auditory stimuli ar e found under anaesthesia as well as in the awake animal. There are th ree types of LC responses to tone: first and by far the most frequent, a burst of several spikes at onset of the tone; second, a burst at to ne offset and lastly, a total inhibition to the tone. All responses pr esent a rapid habituation after the first few presentations of the sti mulus. The results support the view that the LC plays a role in mediat ing responses to environmental changes.