Polysynaptic long-term potentiation: A physiological role of the perforant path-CA3/CA1 pyramidal cell synapse

Chronic stimulating and recording electrodes were implanted in the perforant path (PP), the dentate gyrus, and the CA3 and CA1 regions in adult rats. Input-output curves were constructed from PP-dentate, dentate-CA3, and CA3-CA1 responses before and after 9 high-frequency trains (400 Hz, 20 ms) delivered to PP. The stimulations produced enhancement of the population spikes at each pathway tested, lasting from 1 to 24 h. It is hypothesized that the potentiating effect in the test pathways (dentate-CA3, CA3-CA1) occurred as a result of coupling the tetanizing trains via the direct PP-CA3/CA1 synapses with the asynchronous polysynaptic volleys occurring in the intrahippocampal circuitry. The findings suggest that the physiological role of the direct PP-pyramidal cell synapse may be to enhance the effectiveness of other inputs to these neurons.

[1]  G. Buzsáki.  Hippocampal sharp waves: Their origin and significance , 1986, Brain Research.

[2]  W. Levy,et al.  Synapses as associative memory elements in the hippocampal formation , 1979, Brain Research.

[3]  G. Buzsáki,et al.  Direct afferent excitation and long-term potentiation of hippocampal interneurons. , 1982, Journal of neurophysiology.

[4]  B. Gustafsson,et al.  Hippocampal long-lasting potentiation produced by pairing single volleys and brief conditioning tetani evoked in separate afferents , 1986, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[5]  R. Racine,et al.  Long-term potentiation phenomena in the rat limbic forebrain , 1983, Brain Research.

[6]  B. McNaughton,et al.  Synaptic enhancement in fascia dentata: Cooperativity among coactive afferents , 1978, Brain Research.

[7]  G. Buzsáki,et al.  Cellular bases of hippocampal EEG in the behaving rat , 1983, Brain Research Reviews.

[8]  J. Winson,et al.  Gating of neuronal transmission in the hippocampus: efficacy of transmission varies with behavioral state. , 1977, Science.

[9]  K. Lee.  Cooperativity among afferents for the induction of long-term potentiation in the CA1 region of the hippocampus , 1983, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[10]  P. Andersen,et al.  Specific long-lasting potentiation of synaptic transmission in hippocampal slices , 1977, Nature.

[11]  O. Steward,et al.  Topographic organization of the projections from the entorhinal area to the hippocampal formation of the rat , 1976, The Journal of comparative neurology.

[12]  F. F. Weight,et al.  Perforant pathway-evoked long-term potentiation of CA1 neurons in the hippocampal slice preparation , 1985, Brain Research.

[13]  T. Bliss,et al.  Long‐lasting potentiation of synaptic transmission in the dentate area of the anaesthetized rabbit following stimulation of the perforant path , 1973, The Journal of physiology.

[14]  B. R. Sastry,et al.  Associative induction of posttetanic and long-term potentiation in CA1 neurons of rat hippocampus. , 1986, Science.

[15]  C. Yamamoto,et al.  Long-term potentiation in thin hippocampal sections studied by intracellular and extracellular recordings , 1978, Experimental Neurology.