Early appearance of cells bearing Na+ channels in developing mouse brain. A quantitative analysis using light microscopic autoradiography.
125I-alpha-Scorpion toxin (alpha-ScTx) binds to a component of the voltage-sensitive Na+ channel. We have previously shown that receptor capacity on dissociated mouse brain cells increases between days 12 and 19 of fetal life as does the expression of neurotoxin-sensitive 22Na+ influx. In the present study we have investigated the distribution of Na+ channels at the cellular level. Quantitative analysis by light-microscopic autoradiography was carried out on dissociated brain cells labeled with 125I-alpha-ScTx at 13, 15 and 18 fetal days. We have shown that at day 13 a large population of cells (39% of total) is alpha-ScTx-labeled, providing direct confirmation for a wide-spread presence of Na+ channels at an early stage of mouse brain development. The subsequent increase in receptor number with age is due both to an increase in alpha-ScTx-labeled cells (to 53% and 97% at days 15 and 18, respectively) and to an increase in the receptor density on these cells (10.9, 12.7 and 34.5 silver grains/1000 microns2 of cell surface for the 3 stages studied).
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D005865:Gestational Age; D007473:Ion Channels / Q000378:metabolism*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D011950:Receptors, Cholinergic / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels
D007473:Ion Channels; D011950:Receptors, Cholinergic; D015222:Sodium Channels; C029574:scorpion toxin receptor; D012964:Sodium