Expression of EPSP/spike potentiation following low frequency and tetanic stimulation in the CA1 area of the rat hippocampus.
Low frequency stimulation (LFS, 1 Hz for 15 min) has been shown to produce an NMDA receptor dependent homosynaptic long-term depression (LTD) of synaptic potentials in the CA1 area of the rat hippocampus. Here we describe experiments aimed at characterizing EPSP/spike (E/S) coupling associated with this form of LTD. Our data show that following LFS neurons have a higher probability of synchronous discharge in response to a population EPSP of fixed slope (E/S potentiation). This E/S potentiation was not significantly enhanced by a tetanic stimulation. When the protocol was reversed, that is, starting with a tetanic stimulus, E/S potentiation was observed which was unaffected by a subsequent LFS. Saturating these synaptic responses to either a maximal or a minimal value produced similar effects on E/S coupling. E/S depression was never encountered. Finally, we found that the expression of E/S potentiation did not require the activation of NMDA receptors. These data suggest that at the level of a local neuronal network in the CA1 area, LFS is not a very powerful tool since the synaptic depression is associated with a potentiation of the population response of these neurons. Furthermore, the expression of E/S dissociation seems different from that of homosynaptic long-term potentiation and LTD.
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000200:Action Potentials; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission
D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate