Autoradiographic localization of a calcium channel antagonist, [3H]nitrendipine, binding site in rat brain.

[3H]Nitrendipine, a calcium antagonist, binds in a saturable fashion (Kd = 1.4 nM, Bmax = 28 pmol/g tissue) to an apparent single class of sites in rat brain sections. Nifedipine and nitrendipine are potent displacers of [3H]nitrendipine binding while verapamil and D-600 are almost inactive. The autoradiographic distribution of [3H]nitrendipine binding shows high concentrations of sites in the hippocampus, in superficial layers of the cortex, in the external plexiform layer of the olfactory bulb and in the cerebellum. Lower levels are found in the striatum and the hypothalamus. Very low densities are observed in most of the remaining areas. The characteristic distribution of[3H]nitrendipine binding sites may help to reveal the mechanism by which calcium regulates brain functions.