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Human brain imaging of nicotinic acetylcholine α4β2* receptors using [ 18 F ] N ifene: Selectivity, functional activity, toxicity, aging effects, gender effects, and extrathalamic pathways
Author(s) -
Mukherjee Jogeshwar,
Lao Patrick J.,
Betthauser Tobey J.,
Samra Gurleen K.,
Pan MinLiang,
Patel Ishani H.,
Liang Christopher,
Metherate Raju,
Christian Bradley T.
Publication year - 2018
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.24320
Subject(s) - nicotinic agonist , biology , nicotinic acetylcholine receptor , human brain , thalamus , agonist , pharmacology , medicine , endocrinology , receptor , neuroscience , biochemistry
Abstract Nicotinic acetylcholinergic receptors (nAChR's) have been implicated in several brain disorders, including addiction, Parkinson's disease, Alzheimer's disease and schizophrenia. Here we report in vitro selectivity and functional properties, toxicity in rats, in vivo evaluation in humans, and comparison across species of [ 18 F]Nifene, a fast acting PET imaging agent for α4β2* nAChRs. Nifene had subnanomolar affinities for hα2β2 (0.34 nM), hα3β2 (0.80 nM) and hα4β2 (0.83 nM) nAChR but weaker (27–219 nM) for hβ4 nAChR subtypes and 169 nM for hα7 nAChR. In functional assays, Nifene (100 μM) exhibited 14% agonist and >50% antagonist characteristics. In 14‐day acute toxicity in rats, the maximum tolerated dose (MTD) and the no observed adverse effect level (NOAEL) were estimated to exceed 40 μg/kg/day (278 μg/m 2 /day). In human PET studies, [ 18 F]Nifene (185 MBq; <0.10 μg) was well tolerated with no adverse effects. Distribution volume ratios (DVR) of [ 18 F]Nifene in white matter thalamic radiations were ∼1.6 (anterior) and ∼1.5 (superior longitudinal fasciculus). Habenula known to contain α3β2 nAChR exhibited low levels of [ 18 F]Nifene binding while the red nucleus with α2β2 nAChR had DVR ∼1.6–1.7. Females had higher [ 18 F]Nifene binding in all brain regions, with thalamus showing >15% than males. No significant aging effect was observed in [ 18 F]Nifene binding over 5 decades. In all species (mice, rats, monkeys, and humans) thalamus showed highest [ 18 F]Nifene binding with reference region ratios >2 compared to extrathalamic regions. Our findings suggest that [ 18 F]Nifene PET may be used to study α4β2* nAChRs in various CNS disorders and for translational research.