QUALITATIVE ENZYME-HISTOCHEMISTRY AND MICROANALYSIS REVEALS CHANGES IN ULTRASTRUCTURAL DISTRIBUTION OF CALCIUM AND CALCIUM-ACTIVATED ATPASES AFTER MICROWAVE IRRADIATION OF THE MEDIAL HABENULA

The localization of calcium and calcium-activated ATPases was investig ated electron microscopically in the medial habenula of mice after who le body irradiation with modulated microwaves. In non-irradiated anima ls calcium-containing precipitates were seen in different subcellular compartments and were often localized on the luminal side of membranes of synaptic vesicles in nerve terminals. At 1 h after 16-Hz modulated microwave irradiation, the number of synaptic vesicles containing cal cium precipitates decreased, and reaction products appeared at new loc ations: in the synaptic clefts and on nonsynaptic surfaces of the neur onal plasma membrane. This modified calcium distribution remained unch anged for 24 h following irradiation. Calcium-activated ''ecto''-local ized ATPase was detected as a punctuated-linear distribution of the re action product outlining whole areas of glial and neuronal plasma memb rane in the habenula of control animals. This pattern did not change o n microwave irradiation. However, a quercetin-sensitive ''endo''-local ized Ca2+-ATPase activity appeared in some nerve terminals 24 h after irradiation. Thus, microwave irradiation can influence neuronal calciu m homeostasis by inducing Ca2+ redistribution across the plasma membra ne and by modifying Ca2+-ATPase activity. However, no direct correlati on between these effects could be demonstrated by the present study.