DIFFERENT PROPERTIES OF CAFFEINE-SENSITIVE CA2+ STORES IN PERIPHERAL AND CENTRAL MAMMALIAN NEURONS

Using indo-1 based microfluorometry for measuring the cytoplasmic free calcium concentration ([Ca2+](i)), the properties of caffeine-induced Ca2+ release from internal stores were studied in rat cultured centra l and peripheral neurones, including dorsal root ganglia (DRG) neurone s, neurones from nucleus cuneatus, CA1 and CA3 hippocampal region and pyramidal neocortical neurones. Under resting conditions the Ca2+ cont ent of internal stores in DRG neurones was high enough to produce caff eine-triggered [Ca2+](i) transients. Caffeine-induced Ca2+ release dep leted internal stores in DRG neurones, but they refilled themselves sp ontaneously up to 81.4 +/- 5.67 % within 10 minutes. In contrast, in a ll types of central neurones the resting Ca2+ content of internal stor es was low, but the stores could be charged by transmembrane Ca2+ infl ux through voltage-operated calcium channels. After charging, the stor es in central neurones spontaneously lost releasable calcium content a nd within 10 minutes they emptied again. We suggest that in sensory ne urones calcium stores are continuously filled by releasable calcium an d after discharge they can refill themselves spontaneously, while in c entral neurones internal calcium stores can be charged by releasable c alcium only transiently.