Ca2+ entry via postsynaptic voltage-sensitive Ca2+ channels can transiently potentiate excitatory synaptic transmission in the hippocampus.
We have studied the role of Ca2+ entry via voltage-sensitive Ca2+ channels in long-term potentiation (LTP) in the CA1 region of the hippocampus. Repeated depolarizing pulses, in the presence of the NMDA receptor antagonist D-APV and without synaptic stimulation, resulted in a potentiation of excitatory postsynaptic potentials (EPSPs) or currents (EPSCs). This depolarization-induced potentiation was augmented in raised extracellular Ca2+ and was blocked by intracellular BAPTA, a Ca2+ chelator, or by nifedipine, a Ca2+ channel antagonist, indicating that the effect was mediated by Ca2+ entry via voltage-sensitive Ca2+ channels. Although the peak potentiation could be as large as 3-fold, the EPSP(C)s decayed back to baseline values within approximately 30 min. However, synaptic activation paired with depolarizing pulses in the presence of D-APV converted the transient potentiation into a sustained form. These results indicate that a rise in postsynaptic Ca2+ via voltage-sensitive Ca2+ channels can transiently potentiate synaptic transmission, but that another factor associated with synaptic transmission may be required for LTP.
Department of Pharmacology, University of California, San Francisco 94143-0450.
D M
DM
Kullmann
D J
DJ
Perkel
T
T
Manabe
R A
RA
Nicoll
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D006168:Guinea Pigs; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D013997:Time Factors
D015220:Calcium Channels; D011810:Quinoxalines; D016194:Receptors, N-Methyl-D-Aspartate; D004533:Egtazic Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D009543:Nifedipine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium