Temporal limits on the rise in postsynaptic calcium required for the induction of long-term potentiation.
The induction of long-term potentiation (LTP) in hippocampal CA1 pyramidal cells requires a rise in postsynaptic intracellular Ca2+ concentration ([Ca2+]i). To determine the time for which Ca2+ must remain elevated to induce LTP, the photolabile Ca2+ buffer diazo-4 was used to limit the duration of the rise in postsynaptic [Ca2+]i following a tetanus. The affinity of diazo-4 for Ca2+ increases approximately 1600-fold upon flash photolysis, permitting almost instantaneous buffering of [Ca2+]i without disturbing resting [Ca2+]i prior to the flash. Photolysis of diazo-4 1 s following the start of the tetanus blocked LTP, while delaying photolysis for more than 2 s had no discernible effect on LTP. Photolyzing diazo-4 at intermediate delays (1.5-2 s) or reducing photolysis of diazo-4 often resulted in short-term potentiation (STP). These results indicate that a tetanus-induced rise in postsynaptic [Ca2+]i lasting at most 2-2.5 s is sufficient to generate LTP. Smaller increases or shorter duration rises in [Ca2+]i may result in STP.
Malenka
R C
RC
Department of Psychiatry, University of California, San Francisco 94143.
Lancaster
B
B
Zucker
R S
RS
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000502:physiology*; D002478:Cells, Cultured; D006624:Hippocampus / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D010782:Photolysis; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000737:chemistry / Q000502:physiology*; D013997:Time Factors
D002118:Calcium