ABSTRACT
The presence of alpha6 subunit containing nicotinic acetylcholine receptors on nigrostriatal dopaminergic neurons has been demonstrated in rodents and monkeys. [(125)I]alpha-conotoxinMII is a radioligand that binds to alpha6, and also alpha3 subunits of nicotinic acetylcholine receptors (nAChRs). In the present study, we have compared the distribution of [(125)I]alpha-conotoxinMII binding in post mortem human tissue from four groups of patients: individuals with dementia with Lewy bodies displaying extra-pyramidal features (DLB + EPF), DLB without extra-pyramidal features (DLB - EPF) Parkinson's disease without dementia (PD) and age-matched controls. Reduced binding was observed in the putamen and caudate in PD and both DLB groups. In DLB patients, the decline was greater in DLB + EPF compared to DLB - EPF group. The declines in nicotinic receptor binding in the striatum were in part paralleled by reductions in the striatal dopamine transporter. In the thalamus, [(125)I]alpha-conotoxinMII binding was significantly reduced in the centromedian nucleus in both DLB groups, and also in the parafascicular nucleus in the DLB - EPF group. In DLB + EPF and PD patients, there was decreased binding in the ventral lateral nucleus. This study demonstrates alterations of alpha6 and/or alpha3 nAChRs binding in DLB and PD, which are likely to relate to extra-pyramidal symptoms.