1. Whole‐cell patch‐clamp recording has been used to study tetanus‐induced synaptic potentiation of dual‐component excitatory postsynaptic currents (EPSCs) in the CA1 region of rat hippocampal slices, following blockade of GABAA and GABAB receptor‐mediated synaptic inhibition. 2. At a holding potential of ‐60 mV, the initial slope of the EPSC (between 10 and 60% of maximum amplitude) provided an accurate measurement of the AMPA receptor‐mediated component, and the amplitude of the EPSC at a latency of 100 ms provided the best estimate of the size of the NMDA receptor‐mediated component. 3. Neurons were voltage clamped for at least 45 min prior to delivery of a tetanus (test intensity, 100 Hz, 1 s). Measurements at 10 and 30 min following the tetanus were used as indications of short‐term potentiation (STP) and long‐term potentiation (LTP), respectively. One set of neurons were voltage clamped at ‐60 mV throughout. These neurons could be subdivided into two populations on the basis of whether or not there was LTP (n = 9), or only STP (n = 6), of the AMPA receptor‐mediated component. A second set of neurons were voltage clamped at ‐60 mV for 30 min and then at ‐50 mV for 15 min before, during and for 30 min following tetanization. In these experiments there was STP but not LTP (n = 8). 4. In all neurons (n = 23), the time course of the potentiation of the NMDA receptor‐mediated component paralleled that of the AMPA receptor‐mediated component. In addition, potentiation of the NMDA and AMPA receptor‐mediated components were of a similar magnitude. 5. These data demonstrate that it is possible to induce LTP by high frequency stimulation after 45 min of whole‐cell recording. Under these conditions, there is a parallel potentiation of the AMPA and NMDA receptor‐mediated components of dual‐component EPSCs. This constitutes the first evidence, from studies of dual‐component synaptic responses, which is consistent with a presynaptic locus of expression of tetanus‐induced STP and LTP in the hippocampus.

Clark, K. A., & Collingridge, G. L. (1995). Synaptic potentiation of dual‐component excitatory postsynaptic currents in the rat hippocampus. The Journal of Physiology, 482(1), 39–52. Portico.