PARALLEL INCREASES IN [ALPHA-I-125]BUNGAROTOXIN BINDING AND ALPHA-7 NICOTINIC SUBUNIT IMMUNOREACTIVITY DURING THE DEVELOPMENT OF RAT HIPPOCAMPAL-NEURONS IN CULTURE

Previous studies have shown that hippocampal neurons cultured at high density express a-bungarotoxin binding sites and have alpha 7 nicotini c acetylcholine receptor subunit immunoreactivity [Barrantes, G,E., Ro gers, A.T., Lindstrom, J. and Wonnacott, S., Brain Res., 672 (1995) 22 8-236]. 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 [alpha -I-125]bungarotoxin is first detectable after 3 days in culture and in creases during the next 12 days in culture, reaching a maximum of appr oximately 30 000 binding sites per cell. This is accompanied, over the same timecourse, by an increase in immunoreactivity for two antibodie s that specifically bind to the alpha 7 subunit. Both cell bodies and processes were labelled by 9 days in culture. The timecourse of alpha 7-type nicotinic receptor expression resembles that previously describ ed for synapse formation in hippocampal cultures. (C) 1997 Elsevier Sc ience Ireland Ltd.