Developmental shift from long-term depression to long-term potentiation at the mossy fibre synapses in the rat hippocampus.
During development, in the CA1 hippocampal region, long-term potentiation (LTP) starts appearing at postnatal (P) day 7 and reaches its maximal expression towards the end of the second postnatal week. However, LTP is often preceded by long-term depression (LTD), an activity-dependent and long-lasting reduction of synaptic strength. LTD can be induced by sustained, low-frequency stimulation of the afferent pathway and is dependent on activation of N-methyl-D-aspartate (NMDA) receptors. We report here that, in the CA3 hippocampal region, during a critical period of postnatal development, between P6 and P14, a high-frequency stimulation train (100 Hz, 1 s) to the mossy fibres in the presence of the NMDA receptor antagonist (+)-3-(2-carboxy-piperazin-4-yl)-propyl-1-phosphonic acid (CPP; 20 microM) induced LTD. The depression of the amplitude of the field excitatory postsynaptic potential (EPSP) was 28 +/- 7% (n = 21). This form of LTD was NMDA-independent and synapse-specific. When a tetanus was applied in the presence of CPP and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 50 microM), which blocked the field EPSP, it failed to induce LTD upon washout of CNQX. LTD was probably postsynaptic in origin since it did not affect paired-pulse facilitation. A rise in extracellular calcium concentration (from 2 to 4 mM) produced LTP instead of LTD. At the end of the second postnatal week, the same high-frequency stimulation train to the mossy fibres induced LTP as in adult neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Battistin
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T
Biophysics Laboratory, International School for Advanced Studies, Trieste, Italy.
Cherubini
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D000818:Animals; D002118:Calcium / Q000502:physiology; D004558:Electric Stimulation; D006624:Hippocampus / Q000166:cytology / Q000254:growth & development* / Q000502:physiology; D017774:Long-Term Potentiation / Q000502:physiology*; D008839:Microelectrodes; D009412:Nerve Fibers / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology; D013569:Synapses / Q000502:physiology*
D010879:Piperazines; D016194:Receptors, N-Methyl-D-Aspartate; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid; D002118:Calcium