New radioligands are in development for nAChRs. Currently, 2-FA, 6-FA, and 5-I-A radiotracers are available, which have affinity to bind to the α4β2 nAChR subtype. Other radiotracers are in development for this subtype, but there is need for radioligands for imaging of other subtypes of nicotinic receptors, including the α7 subtype, which is abundant in humans. Future research is likely to focus on radioligands for imaging α4β2 nAChR in the thalamus with faster kinetics than 2-FA, 6-FA, and 5-I-A. Radiolabeled antagonists for imaging of α4β2 nAChR may prove very beneficial for greater understanding of receptor binding and ultimately in development of pharmacological agents to help with quitting smoking (Pomper et al. 2005; Horti et al. 2006).
