Effect of D-2 amino-5-phosphonopentanoate and nifedipine on postsynaptic calcium changes associated with long-term potentiation in hippocampal CA1 area.
The induction of long-term potentiation (LTP) in CA1 hippocampal area requires a rise in intracellular postsynaptic calcium. Two major calcium mechanisms may mediate the transmembrane calcium influxes that contribute to this calcium accumulation: the N-methyl-D-aspartate (NMDA) receptor channels, which are voltage dependent and have large calcium permeability and voltage-dependent calcium channels (VDCCs). We have addressed the relative contribution of these routes of calcium entry before and during LTP expression, in synaptically evoked dendritic calcium transients from a population of CA1 pyramidal neurons. Combining the use of the fluorescent calcium indicator Fura-2 with field potential measurements, we observed that the calcium transients evoked by single stimuli, during the maintenance phase of LTP, were enhanced. These transients were not affected by D-2 amino-5-phosphonopentanoate (D-APV) (50 microM), an antagonist of NMDA receptors but were reduced by approximately one-quarter, in the presence of the L-type VDCCs blocker nifedipine (10 microM). During tetanic stimulation (100 Hz, 1 s) the components triggered by the activation of those two calcium mechanisms had comparable magnitudes representing the sum about half of the intracellular calcium accumulation. Thus, following both single and high frequency stimulation, a substantial fraction of calcium entry may occur through other types of VDCCs or be due to calcium release from intracellular stores.
Matias
Carlos M
CM
Department of Physics, University of Trás-os-Montes and Alto Douro (UTAD), 5001-911 Vila Real, Portugal.
Dionísio
José C
JC
Arif
Mona
M
Quinta-Ferreira
Maria Emília
ME
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects*; D005456:Fluorescent Dyes; D016257:Fura-2; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D015640:Ion Channel Gating; D017774:Long-Term Potentiation; D009543:Nifedipine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013569:Synapses / Q000502:physiology*
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D005456:Fluorescent Dyes; D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate; D009543:Nifedipine; D016257:Fura-2