MOLECULAR PHARMACOLOGY, 41:31-37 A Subtype of Nicotinic Cholinergic Receptor in Rat Brain Is Composed of a4 and 32 Subunits and Is Up-regulated by Chronic Nicotine Treatment

The subunit composition and pharmacological regulation of rat neuronal nicotinic cholinergic receptors were assessed. Specific immunoprecipitation was determined in solubilized rat brain ho-mogenates using [3H]cytisine, a high affinity agonist at nicotinic receptors, in conjunction with polyclonal antisera generated against nonhomologous domains of the various subunits corn-posing this receptor class. In all brain regions tested, only anti-sera generated against the a4 and fl2 subunits were able to immunoprecipitate specifically receptors labeled by [3H]cytisine. Thus, these sera were further characterized in order to validate and optimize their use in the immunoprecipitation protocol. Prein-cubation of solubilized receptors from rat forebrain with antisera generated against the a2, a3, a5, 133, or $4 subunits did not decrease the amount of precipitable a4 or fl2 subunit. On the other hand, when either anti-a4 or anti-fl2 serum was used t