Nicotinic regulation of the hemicholinium-3-sensitive choline transporter in the mouse striatum

Nicotine (NIC) acting via nicotinic receptors (nAChRs) has been shown to influence autonomic, cognitive and motor functions. Endogenously, nAChRs are activated by cholinergic neurotransmitter acetylcholine (ACh). The high-affinity choline uptake (NACU), mediated by the hemicholinium-3 (HC-3) sensitive, Na + and Cl--coupled, presynaptic choline transporter (CHT), is rate-limiting in the biosynthesis of ACh. The overall hypothesis of the proposed research is that NIC via nAChR activation alters CHT function. This hypothesis was tested via three specific aims: (1) nAChR activation alters CHT function, (2) nAChR activation alters CHT surface redistribution and (3) nAChR activation alters choline uptake dynamics. In C57BL/6 mice, administration of NIC reduced the maximal transport capacity (Vmax) of CHT in striatum. The effect of NIC was recapitulated in vitro in striatal slices, but not in synaptosomes. Biotinylation assays revealed that the reduction in Vmax of CHT following in vitro, but not in vivo, NIC administration is accompanied by a reduction in the surface distribution of CHT in the striatum. The effects of NIC on CHT function and surface expression were abolished by nAChR antagonist, mecamylamine. Choline clearance dynamics were examined in the striatum of urethane anethetized mice, using in vivo amperometry. Exogenous choline (40 mM) pressure ejection elicited a 2-fold increase in choline signal amplitude, after systemic NIC administration as compared to choline signals derived via systemic saline injection. The onset of nicotine response in the striatum occurred ∼5 min after injection. These findings in the striatum support the overall hypothesis that NIC via nAChR alters CHT function. Thus, this research provides a novel mechanism of NIC action in influencing autonomic, cognitive and motor function.; Keywords. Nicotinic Receptors, Choline Transporters, Striatum, Nicotine, In vivo Amperometry...