Comparative Analysis of Nicotine-Like Receptor-Ligand Interactions in Rodent Brain Homogenate |
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Authors: | Christer Larsson Agneta Nordberg |
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Affiliation: | Department of Pharmacology, Uppsala University, Uppsala, Sweden |
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Abstract: | The effects of different variables such as incubation time, temperature, tissue protein content, and pH on the interactions of various labelled nicotinic ligands with nicotine-like binding sites in vitro were studied in rodent brain preparations. The ligands tested were alpha-[3H]bungarotoxin (alpha-[3H]BTX), [3H]tubocurarine ([3H]TC), and [3H]nicotine ([3H]NIC). The regional distribution of the labelled nicotinic ligand binding was also studied and affinity constants and maximal binding (Bmax) values for the equilibrium [3H]NIC binding are given. Association kinetics for [3H]NIC and [3H]TC binding to brain homogenate were similar, with maximal binding within 5-10 min of incubation, followed by a continuous decrease. In contrast, the binding of alpha-[3H]BTX to brain homogenate was much slower, reaching equilibrium after 30-60 min of incubation. Scatchard analysis of equilibrium binding data for [3H]NIC in the hippocampus indicated two binding sites: a high-affinity site (Bmax, 60 pmol/g protein; KD, 6 nM) and a low-affinity site (Bmax, 230 pmol/g protein; KD, 125 nM). The data for the high-affinity [3H]NIC binding site are very similar to previously found data for the high-affinity binding site of [3H]TC and the binding site of alpha-[3H]BTX. Each ligand showed regional differences in binding, and the binding pattern also differed between the ligands. |
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Keywords: | α-[3H]Bungarotoxin [3H]Nicotine [3H]Tubocurarine Nicotine-like binding sites Methodological aspects Comparative analysis |
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