title: Long-term Potentiation of NMDA Receptor-mediated EPSP in Guinea-pig Hippocampal Slices.
abstract: Hippocampal slices from guinea-pigs were used to examine the long-term potentiation (LTP) of the N-methyl-d-aspartate (NMDA)-mediated excitatory postsynaptic potential (EPSP). Intracellular recordings were performed from CA1 pyramidal neurons in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 5 - 10 microM) and picrotoxin (50 microM). In these experimental conditions test stimuli applied at low frequency (0.1 Hz) to the Schaffer collateral - commissural pathway evoked a prolonged EPSP (150 - 200 ms). To obtain this CNQX-resistant EPSP, stimulus intensities had to be raised above the level required to evoke an EPSP of comparable amplitude in physiological solution. Tetanic stimulation (two trains of 100 Hz, 1 s every 20 s) led to a potentiation of the CNQX-resistant EPSP, and this potentiated response was abolished with d-(-)-2-amino-5-phosphonovaleric acid (50 microM). The potentiation of the NMDA receptor-mediated EPSP was more pronounced for strong than for weak test stimuli, and was suppressed when test EPSPs were evoked during membrane hyperpolarization. These results suggest that NMDA receptor-mediated responses can undergo LTP, and hence can contribute to the maintenance of LTP.
authors.affiliation: Department of Physiology and Biochemistry 'G. Moruzzi', Via S. Zeno 31, University of Pisa, 56127 Pisa, Italy.
authors.forename: N.
authors.initials: N
authors.lastname: Berretta
authors.forename: F.
authors.initials: F
authors.lastname: Berton
authors.forename: R.
authors.initials: R
authors.lastname: Bianchi
authors.forename: M.
authors.initials: M
authors.lastname: Brunelli
authors.forename: M.
authors.initials: M
authors.lastname: Capogna
authors.forename: W.
authors.initials: W
authors.lastname: Francesconi