Eur. J. Neurosci., Vol. 10, Suppl. 10, 14.52 (1998)
Properties of the tetanic and post-tetanic components of intradendritic Ca2+ signals in hippocampal CA1 neurons
T. Jäger, K.G. Reymann and T. Behnisch
Combining confocal microscopy with the Ca2+ indicator Calcium Green-1 and intracellular recordings we analysed Ca2+ rises, evoked by different plasticity-relevant tetanizations. Data analysis revealed, that the normalized total area of fluorescence intensity changes (F/Fo) was correlated both to the strength and the duration of tetanization. The normalized area of fluores-cence intensity changes during the time of tetanization (tetanic component) was correlated linearly to the tetanization duration (r=0.96). The tetanic component strongly determined the area of the post-tetanic Ca2+ signal. The normalized relationship of the post-tetanic Ca2+ signal to the total Ca2+ change decreased when the tetanization duration was prolonged. In contrast, with an increased stimulation strength, a positive correlation of the relationship of the post-tetanic component to the total amount Ca2+ could be observed. Determination of the decay times of the averaged Ca2+ transients revealed, that the single exponential fit gives the best description of the decaying Ca2+ signal. We found a strong dependence between the time constant and the tetanization duration which indicates that the time constant is not uniform but dependent upon the employed tetanization. Interestingly, the time constants are clearly dependent on the Ca2+ rise during active tetanization. We conclude, that augmenting the stimulation strength leads to a respective increase of the post-tetanic Ca2+ portion within the total Ca2+ signal, whereas a prolongation of the tetanization duration does not.
This work was supported by the DFG (SFB 426).
