Pleiotrophin inhibits hippocampal long-term potentiation: A role of pleiotrophin in learning and memory

Pleiotrophin (PTN) is a growth factor that has been shown to be involved in hippocampal synaptic plasticity and learning. To further understand the involvement of PTN in memory processes, we performed in vitro electrophysiological studies in PTN-stimulated CA1 from rat hippocampal slices combined with the behavioural testing of PTN deficient (PTN-/-) mice. We found that PTN inhibited hippocampal long-term potentiation (LTP) induced by high-frequency stimulation (HFS) consisted in three trains of 100 Hz separated by 20 s. To test the possibility that PTN might be involved in behavioural memory processes, we tested the learning behaviour of PTN-/- mice using the Y-maze test. We did not observe significant differences in recognition memory between PTN-/- and Wild Type (WT) mice when a 30 min-interval intertrial (ITI) was used in the Y-maze test. However, whereas WT mice showed disruption of recognition memory using a 60 min-ITI, PTN-/- mice maintained the recognition memory. The data demonstrate that PTN inhibits hippocampal LTP in vitro and might play a role in memory processes in vivo.