Receptor regulation

Abstract

The study of factors that regulate neuronal nicotinic acetylcholine receptors has been impeded by the lack of a suitable in vitro system. Thus, we have used a primary neuronal cell culture system from embryonic day 18 rat fetal brain stem (including the thalamus, hypothalamus, midbrain and pons) and have characterized [³H]cytisine binding to nicotinic acetylcholine receptors present in these primary neurons. Our results demonstrate that after 15 days in culture [³H]cytisine binding to brain stem neurons is saturable and specific, with a Kd of 0.7 nM and a Bmax of ≈ 50 fmol/mg protein. [³H]Cytisine binding was competitively displaced by nicotine with an IC₅₀ of 20 nM and by carbachol and dihydro-ß-erythroidine with IC₅₀ values of <1 uM. These studies indicate that this cell culture system may be a suitable model in which to elucidate the properties of neuronal nicotinic acetylcholine receptors, to define the subunit composition of the receptors labeled by high affinity nicotinic ligands and to study the mechanisms involved in the regulation of these receptors. This work was supported by NIH grants DA05417 and DA06486.