The role of calcium in short-term potentiation in the rat hippocampal slice.
Short-term potentiation of extracellular field excitatory postsynaptic potentials (EPSP's) was investigated in the stratum radiatum of CA1 of the rat hippocampal slice in vitro. A presynaptic tetanus consisting of a single train of stimuli at 250 Hz evoked short-term potentiation (STP), but not long-term potentiation (LTP) of small amplitude, just suprathreshold, EPSP's in a medium containing 2 mM Ca and 2 mM Mg. Increasing the number of stimuli in the tetanus enhanced the initial amplitude of the STP to a maximum of 40-70% with 30-40 stimuli, and enhanced the decay time constant of STP to a maximum of 60-80 s. Increasing the Ca influx by raising external Ca, lowering Mg or adding the agent 4-aminopyridine caused a large increase in the initial amplitude of STP but only a very slight increase in the decay time of STP. LTP was frequently evoked in high Ca/Mg ratios of 2.0 or 4.0, but not in 1.0 or 0.5.
Anwyl
R
R
Department of Physiology, Trinity College, Dublin, Eire.
Lee
W L
WL
Rowan
M
M
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D004558:Electric Stimulation; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology*
D008274:Magnesium; D002118:Calcium