The characteristics of LTP induced in hippocampal slices are dependent on slice-recovery conditions.
In area CA1 of hippocampal slices which are allowed to recover from slicing "in interface" and where recordings are carried out in interface, a single 1-sec train of 100-Hz stimulation triggers a short-lasting long-term potentiation (S-LTP), which lasts 1-2 h, whereas multiple 1-sec trains induce a long-lasting LTP (L-LTP), which lasts several hours. Moreover, the threshold and the features of these LTP depend on the history of the neurons, a phenomenon known as metaplasticity. Here, where all recordings were performed in interface, we found that allowing the slices to recover "in submersion" had dramatic metaplastic effects. In these conditions, a single 1-sec train at 100 Hz induced an L-LTP which lasted at least 4 h and was dependent on protein synthesis. Interestingly, this type of metaplasticity was observed when the concentration of Mg(++) used was 1.0 mM but not when it was 1.3 mM. The LTP induced by four 1-sec trains at 100 Hz was similar whatever the incubation method. However, the signaling cascades recruited to achieve that pattern were different. In the interface-interface paradigm (recovery and recording both in interface) the four-train induced LTP recruited the PKA signaling pathway but not that of the p42/44MAPK. On the contrary, in the submersion-interface paradigm the four-train induced LTP recruited the p42/44MAPK signaling pathway but not that of the PKA. To our knowledge this is the first example of metaplasticity involving the recruitment of signaling cascades in LTP.
Capron
Brigitte
B
Department of Neurosciences, University of Mons-Hainaut, 7000 Mons, Belgium.
Sindic
Christian
C
Godaux
Emile
E
Ris
Laurence
L
D000818:Animals; D004558:Electric Stimulation; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology*; D008274:Magnesium / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D009474:Neurons / Q000201:enzymology; D009924:Organ Culture Techniques / Q000379:methods*; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
D011494:Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D008274:Magnesium