Pharmacological and null mutation approaches reveal nicotinic receptor diversity.
We have developed an array of assays for nicotinic acetylcholine receptor binding and function. [125I]alpha-Bungarotoxin-, (-)-[3H]nicotine-, and [3H]epibatidine-binding nicotinic acetylcholine receptors were assayed in mouse brain membranes and sections. Nicotinic acetylcholine receptor function was quantified using synaptosomal [3H]dopamine, [3H]gamma-aminobutyric acid ([3H]GABA), and 86Rb(+) efflux techniques. Additionally, the effects of beta2 subunit deletion on each of the measures were assessed. Detailed pharmacological comparison revealed minimally six nicotinic binding subtypes: [125I]alpha-bungarotoxin-binding nicotinic acetylcholine receptors; beta2-subunit-dependent and -independent high-affinity (-)-[3H]nicotine-binding sites; beta2-dependent and -independent cytisine-resistant [3H]epibatidine-binding sites; and a beta2-dependent low-affinity [3H]epibatidine binding site. Comparative pharmacology suggested that [3H]GABA and dihydro-beta-erythroidine (DHbetaE)-sensitive 86Rb(+) efflux are mediated by the same (probably alpha4beta2) nicotinic acetylcholine receptor subtype, while other nicotinic acetylcholine receptor subtypes evoke [3H]dopamine and DHbetaE-resistant 86Rb(+) efflux. In whole-brain preparations, each measure of nicotinic acetylcholine receptor function was beta2 dependent. The majority of beta2-independent [3H]epibatidine binding was located in small, scattered brain nuclei, suggesting that individual nuclei may prove suitable for identification of novel, native nicotinic acetylcholine receptors.
Whiteaker
P
P
Institute for Behavioral Genetics, University of Colorado, Campus Box 447, Boulder, CO 80303-0447, USA.
Marks
M J
MJ
Grady
S R
SR
Lu
Y
Y
Picciotto
M R
MR
Changeux
J P
JP
Collins
A C
AC
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D014644:Genetic Variation; D005838:Genotype; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D018722:Nicotinic Agonists / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*; D014316:Tritium
D019086:Bridged Bicyclo Compounds, Heterocyclic; D018722:Nicotinic Agonists; D011725:Pyridines; D011978:Receptors, Nicotinic; D014316:Tritium; C082748:epibatidine