Olfactory tubercle's different neural elements activated by locus coeruleus

Olfactory tubercle (OT) evoked potentials were recorded following single pulse stimulation of the locus coeruleus (LC) in cats. Also, OT unit responses were recorded extracellularly following LC repetitive stimulation in rats. In order to characterize the properties of OT evoked potentials, these responses were evaluated following repetitive stimulation, paired shock, animal asphyxiation and damage to the recording site. Longer latency potential changes were more labile to repetitive stimulation, paired shock and asphyxiation than short latency changes. The time course of the effects following experimental procedures was not equal for the potentials of different latencies. Most of the individual OT neurons studied were not affected by repetitive LC stimulation. However, a small percentage were enhanced and the remainder decreased discharge frequency. Hypertensive effects were ruled out as a cause of the OT unit responses following LC stimulation because the temporal course of both events were not similar. Results of both electrophysiological techniques suggest that the LC influences different neural elements and/or neural populations within the OT. These responses appear to be independent of one another.