Nicotinic Receptor Loss in Brain of Alzheimer Patients as Revealed by In Vitro Receptor Binding and In Vivo Positron Emission Tomography Techniques

Abstract

Heterogenous nicotinic receptor subtypes exist in brain. In vitro receptor binding of 3H-nicotine to tissue homogenates from cortical autopsy brain tissue from patients with Alazheimer’s disease indicates a marked loss in the high affinity nicotinic binding sites concomittant with a change in the proportion of high and low affinity nicotinic binding sites. When 11C-nicotine is given intravenously to Alzheimer patients in order to in vivo visualize the nicotinic receptors a lower uptake of 11C radioacitivity to the brain is observed compared to healthy volunteers. A significant larger difference between the uptake of the two enantiomers (S) (−) and (R) (+) 11C-nicotine is observed in Alzheimer brains compared to healthy controls. This observation might be of diagnostic importance.