Modification of cortical, reticular and hippocampal unit activity by nicotine in the rabbit

¹ Department of Anatomy, School of Medicine, University of California, Los Angeles, and the Veterans Administration Hospital, Sawtelle, California

Of the three regions examined, the hippocampus had the lowest threshold for nicotine effects. Following nicotine injection, regularization of the EEG in all regions was accompanied by increased unit excitability, and during seizures the unit activity was depressed. Modification of neocortical and reticular unit activity without any concomitant EEG changes in these regions was occasionally recorded after nicotine injection. Further experiments indicated that these changes of unit activity were due to alterations in hippocampal excitability elicited by the drug. Electrical stimulation of the hippocampus which evoked regularization and seizure discharges similarly modified the reticular unit excitability, but no conclusive results could be obtained regarding the hippocampal influence on neocortical units.