The striatum plays an important role in linking cortical activity to basal ganglia outputs. We conducted the calcium (Ca²⁺) imaging to investigate the spontaneous activities of the striatum using acute slice preparations. The corticostriatal slices of rats were stained with Fura-PE3-AM. Long lasting spontaneous intracellular Ca²⁺ ([Ca²⁺]_i) changes, which lasted up to several hundreds seconds, were observed. The amplitudes and the intervals of the changes were variable even in a single cell. Most cells exhibited irregular frequencies, but some exhibited oscillatory features. Most of these [Ca²⁺]_i changes were not suppressed by TTX, blocker of action potentials. The number of the active cells, which exhibited the [Ca²⁺]_i changes, was greatly reduced by the intracellular Ca²⁺ store depletor, thapsigargin. Therefore, the intracellular Ca²⁺ store is likely to contribute to the [Ca²⁺]_i transients.
The [Ca²⁺]_i changes under standard ACSF and TTX showed different levels of regularity. We tested synchronization of the [Ca²⁺]_i changes between cell pairs under the both conditions. The number of synchronized cell pairs reduced in TTX. These results suggested that TTX insensitive and slow rate [Ca²⁺]_i changes might exert the information processing in the striatum.