Dose-response relationships of intranasal cholecystokinin and the P300 event-related brain potential

The gut and brain peptide cholecystokinin (CCK) has been found to improve controlled stimulus processing and attention as indicated by the late positive complex (LPC) of the event-related brain potentials (ERPs). A direct nose-brain pathway for cortical effects of intranasally administered CCK-8S has been described, although the precise transmission within this pathway is still unknown. The present study compared the effects of two doses of CCK-8S (10 and 20 mug) and placebo after intranasal administration on the LPC of the ERP in healthy male and female subjects to further elucidate mechanisms of this nose-brain pathway. ERPs were recorded in an oddball-paradigm. Results showed that both doses of CCK-8S induced a positive shift of the ERP. This effect did not differ between the 10 and 20 mug dosage of CCK-8S. The results indicate that a saturable mechanism may be responsible for the transmission of CCK-8S from the nose into the brain, since both doses of CCK-8S induced comparable increases of the ERP subcomponents. (C) 2002 Elsevier Science Inc. All rights reserved.