Autoradiographic localization of tetrodotoxin-sensitive Na+ channels in rat brain.

The localization of tetrodotoxin-sensitive Na+ channels in rat brain was studied using a tritiated derivative of tetrodotoxin. The autoradiographic distribution of a tritiated ethylenediamine derivative of tetrodotoxin [( 3H]en-TTX) binding showed a high concentration of sites in cortical layers, hippocampus, globus pallidus, substantia nigra and the molecular layer of the cerebellar cortex. Lower levels were found principally in the striatum and median forebrain bundle. The white matter was not labelled. The characteristic distribution of tetrodotoxin-sensitive Na+ channels was compared to that of nitrendipine-sensitive Ca2+ channels and to that of apamin-sensitive Ca2+-dependent K+ channels.