CHARACTERIZATION OF NICOTINIC RECEPTORS IN IMMORTALIZED HIPPOCAMPAL-NEURONS

Nicotinic acetylcholine receptors, particularly nicotinic alpha-bungar otoxin (alpha-BGT) receptors, are present in relatively high concentra tions in rat hippocampus. Because of the difficulties encountered in s tudying receptors using primary cells in culture, especially for bioch emical work, we investigated the possibility of using an immortalized cell line from embryonic rat hippocampus (H19-7). RNase protection ass ays show that alpha 4, alpha 7 and beta 2 neuronal nicotinic receptor subunit mRNAs are present in differentiated but not undifferentiated H 19-7 cells, while alpha 2, alpha 3, alpha 5 and beta 3 subunit mRNAs w ere not detectable under either condition. In line with these results, the present data demonstrate that the H19-7 cells express cell surfac e nicotinic alpha-BGT binding sites, which were maximal after seven da ys of differentiation in culture. The receptors were saturable, of hig h affinity (K-d = 1.30 nM and B-max = 11.70 fmol/10(5) cells) and had a pharmacological profile similar to that observed for CNS alpha-BGT r eceptors. On the other hand, although alpha 4 and beta 2 neuronal nico tinic subunit mRNAs were present in differentiated H19-7 cells, no [H- 3]cytisine binding was observed. Because immortalized cell lines have the advantage that they provide a limitless supply of cells as compare d to primary cell cultures, but yet are not malignant in origin, the p resent results may suggest that the H19-7 immortalized hippocampal cel l line represent a useful CNS model system for examining alpha-BGT nic otinic receptors.