Related Experiment Videos
PET quantification of specific binding of carbon-11-nicotine in human brain
R F Muzic1, M S Berridge, R P Friedland
1Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA.
Unlabelled:
Previous work on the PET measured uptake of (S)-[11C]nicotine presents conflicting findings as to whether it reflects specific binding.
Methods:
We studied the uptake of (R)-[11C]nicotine and (S)-[11C]nicotine in normal volunteers at baseline conditions and after a challenge with unlabeled (S)-nicotine to decrease the concentration of free binding sites or with CO2 to increase perfusion. We analyzed the data using two- and three-compartment models.
Results:
We found tissue pharmacokinetics of (R)- and (S)-[11C]nicotine are adequately described by the two-compartment model. (S)-nicotine challenge induced small but statistically significant reductions in distribution volume (DV) of both (R)- and (S)-[11C]nicotine. The changes in DV could not be attributed to perfusion changes because DV was not affected by CO2 challenge. Although the reduction in DV indicates sensitivity of [11C]nicotine to status of nicotinic binding sites, the small magnitude of the reduction suggests that most nicotine uptake is nonspecific.
Conclusion:
Although differences in DV attributable to specific binding were detected, (R)- and (S)-[11C]nicotine are relatively poor tracers for studying nicotinic binding sites using PET.