Parallel increases in [α-125I]bungarotoxin binding and α7 nicotinic subunit immunoreactivity during the development of rat hippocampal neurons in culture

Previous studies have shown that hippocampal neurons cultured at high density express α-bungarotoxin binding sites and have α7 nicotinic acetylcholine receptor subunit immunoreactivity [Barrantes, G.E., Rogers, A.T., Lindstrom, J. and Wonnacott, S., Brain Res., 672 (1995) 228–236]. We now examine both of these parameters in well-characterized hippocampal neurons cultured at sufficiently low densities to resolve individual neurons and their processes. The specific binding of [α-125I]bungarotoxin is first detectable after 3 days in culture and increases during the next 12 days in culture, reaching a maximum of approximately 30 000 binding sites per cell. This is accompanied, over the same timecourse, by an increase in immunoreactivity for two antibodies that specifically bind to the α7 subunit. Both cell bodies and processes were labelled by 9 days in culture. The timecourse of α7-type nicotinic receptor expression resembles that previously described for synapse formation in hippocampal cultures.