Analysis of the tetanic and post-tetanic components of intradendritic Ca2+ signals in hippocampal CA1 neurons.
The importance of both the activation of second messenger cascades and an increase of the intracellular Ca2+ concentration for the induction of synaptic plasticity in hippocampal CA1 neurons is well established. Using the dye Calcium Green-1, we analysed the Ca2+ increases evoked by different 100-Hz tetanization paradigms commonly used to induce long-term potentiation. We found that the normalized total area of fluorescence intensity changes (F/F0) was correlated with both the strength and the duration of tetanization. Furthermore, the normalized area of fluorescence intensity changes during the time of tetanization (tetanic component) correlated strongly in a linear manner with the tetanization duration. Moreover, the tetanic component strongly determined the area of the post-tetanic Ca2+ signal. Interestingly, the normalized relationship of the post-tetanic Ca2+ signal to the total Ca2+ change decreased with prolonged tetanizations. 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 obtained. The time constants of the Ca2+ extrusion depend linearly on both the tetanization duration and the amount of the tetanic Ca2+ signal. Our data demonstrate 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. Thus, no further significant prolongation of the Ca2+ signal occurs during increased durations of tetanization.
Jäger
T
T
Federal Institute for Neurobiology, Department of Neurophysiology, Magdeburg, Germany.
Reymann
K G
KG
Behnisch
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003712:Dendrites / Q000502:physiology*; D004558:Electric Stimulation; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D018613:Microscopy, Confocal / Q000295:instrumentation / Q000379:methods; D009473:Neuronal Plasticity; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology*
D002118:Calcium