60Co and 45Ca autoradiography in cerebral ischemia in the rat

Radioisotopes of divalent Co (57Co in single photon emission tomography (SPECT)and 55Co in positron emission tomography (PET) have clinically been applied to visualize Ca related brain damage. The cerebral uptake of 45Ca and 60Co in a unilateral stroke model in the rat was compared; 100 microCi 45CaCl2 or 60 microCi 60CoCl2 was intravenously given at day 2 or 9 and the rats were killed 24 h later for autoradiography. Similarly increased uptake of 45Ca and 60Co was observed at both time points in unilaterally affected areas such as the cerebral cortex, dentate gyrus, caudate putamen of the striatum, substantia nigra pars reticulatum and corpus geniculatum. More Ca-uptake was found in the hippocampus CA1 region (at day 10) and the thalamus (ventral part at both time points). Radioactive Co but not Ca accumulated in the choroid plexus. Although the present investigation supports the idea that divalent Co-isotopes are useful to visualize stroke induced damage and choroid plexus function, these radionuclides do, however, not allow to detect excessive Ca-influx in degenerating neurones.