@article {Grinevich1011, author = {Vladimir P. Grinevich and Peter A. Crooks and Sangeetha P. Sumithran and Aaron J. Haubner and Joshua T. Ayers and Linda P. Dwoskin}, title = {N-n-Alkylpyridinium Analogs, a Novel Class of Nicotinic Receptor Antagonists: Selective Inhibition of Nicotine-Evoked [3H]Dopamine Overflow from Superfused Rat Striatal Slices}, volume = {306}, number = {3}, pages = {1011--1020}, year = {2003}, doi = {10.1124/jpet.103.051789}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Structural simplification of N-n-alkylnicotinium analogs, antagonists at neuronal nicotinic acetylcholine receptors (nAChRs), was achieved by removal of the N-methylpyrrolidino moiety affording N-n-alkylpyridinium analogs with carbon chain lengths of C1 to C20. N-n-Alkylpyridinium analog inhibition of [3H]nicotine and [3H]methyllycaconitine binding to rat brain membranes assessed interaction with α4β2* and α7* nAChRs, respectively, whereas inhibition of nicotine-evoked 3H overflow from [3H]dopamine ([3H]DA)-preloaded rat striatal slices assessed antagonist action at nAChR subtypes mediating nicotine-evoked DA release. No inhibition of [3H]methyllycaconitine binding was observed, although N-n-alkylpyridinium analogs had low affinity for [3H]nicotine binding sites, i.e., 1 to 3 orders of magnitude lower than that of the respective N-n-alkylnicotinium analogs. These results indicate that the N-methylpyrrolidino moiety in the N-n-alkylnicotinium analogs is a structural requirement for potent inhibition of α4β2* nAChRs. Importantly, N-n-alkylpyridinium analogs with n-alkyl chains \< C10 did not inhibit nicotine-evoked [3H]DA overflow, whereas analogs with n-alkyl chains ranging from C10 to C20 potently and completely inhibited nicotine-evoked [3H]DA overflow (IC50 = 0.12-0.49 μM), with the exceptions of N-n-pentadecylpyridinium bromide (C15) and N-n-eicosylpyridinium bromide (C20), which exhibited maximal inhibition of \~{}50\%. The mechanism of inhibition of a representative analog of this structural series, N-n-dodecylpyridinium iodide, was determined by Schild analysis. Linear Schild regression with slope not different from unity indicated competitive antagonism at nAChRs mediating nicotine-evoked [3H]DA overflow and a KB value of 0.17 μM. Thus, the simplified N-n-alkylpyridinium analogs are potent, selective, and competitive antagonists of nAChRs mediating nicotine-evoked [3H]DA overflow, indicating that the N-methylpyrrolidino moiety is not a structural requirement for interaction with nAChR subtypes mediating nicotine-evoked DA release. The American Society for Pharmacology and Experimental Therapeutics}, issn = {0022-3565}, URL = {https://jpet.aspetjournals.org/content/306/3/1011}, eprint = {https://jpet.aspetjournals.org/content/306/3/1011.full.pdf}, journal = {Journal of Pharmacology and Experimental Therapeutics} }