Commissural synapses, but not mossy fiber synapses, in hippocampal field CA3 exhibit associative long-term potentiation and depression.
When CA3 commissural afferents received low-frequency (weak) stimuli synchronized with a train of mossy fiber bursts (strong), associative long-term potentiation (LTP) was induced at mixed commissural and associational synapses on hippocampal CA3 pyramidal cells in vitro. In contrast, a weak mossy fiber input did not potentiate when given in phase with commissural/associational bursts. Furthermore, commissural/associational synapses receiving low-frequency stimuli out-of-phase with strong rhythmic mossy fiber input showed associative long-term depression (LTD), whereas mossy fiber synaptic strengths were not depressed when they received weak inputs out-of-phase with a strong commissural/associational input. Thus, both associative LTP and associative LTD can be induced at commissural/associational synapses, but not at mossy fiber synapses.
Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218.
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Chattarji
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Stanton
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Sejnowski
D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009433:Neural Inhibition; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000502:physiology*