Abstract
1. The effects of small amounts of nicotine on electrocortical activity and central acetylcholine (ACh) release have been studied on anaesthetized cats.2. The most common effect of nicotine given intravenously in a dose of 2 mug/kg every 30 sec for 20 min was to cause desynchronization of the electrocorticogram, indicating cortical activation, and an increase in the release of cortical ACh.3. A larger dose given less frequently (4 mug/kg every min for 20 min) caused, in some experiments, an increase and in others a decrease in cortical activity. Such changes were accompanied respectively by an increase or decrease in cortical ACh output.4. The amounts of nicotine that affected the electrocorticogram and ACh release are probably similar to those absorbed by the cigarette smoker who inhales.5. The effects of nicotine on the electrocorticogram were transient, but the effects on ACh were prolonged. This suggests that at least two pathways are involved in the nicotine response.