Attenuated LTP in hippocampal dentate gyrus neurons of mice deficient in the PAF receptor

Platelet-activating factor (PAF), a bioactive lipid (1-O-alkyl-2-acetyl-sn- glycero-3-phosphocholine) derived from phospholipase A(2) and other pathway s, has been implicated in neural plasticity and memory formation. Long-term potentiation (LTP) can be induced by the application of PAF and blocked by a PAF receptor (PAF-R) inhibitor in the hippocampal CA1 and dentate gyrus. To further investigate the role of PAF in synaptic plasticity, we compared LTP in dentate granule cells from hippocampal slices of adult mice deficie nt in the PAF-R and their age-matched wild-type littermates. Whole cell pat ch-clamp recordings were made in the current-clamp mode. LTP in the perfora nt path was induced by a high-frequency stimulation (HFS) and defined as >2 0% increase above baseline of the amplitude of excitatory postsynaptic pote ntials (EPSPs) from 26 to 30 min after HFS. HFS-induced enhancement of the EPSP amplitude was attenuated in cells from the PAF-R-deficient mice (163 /- 14%, mean +/- SE; n = 32) when compared with that in wild-type mice (219 +/- 17%, n = 32). The incidence of LTP induction was also lower in the cel ls from the deficient mice (72%, 23 of 32 cells) than in the wild-type mice (91%, 29 of 32 cells). Using paired-pulse facilitation as a synaptic pathw ay discrimination, it appeared that there were differences in LTP magnitude s in the lateral perforant path but not in the medial perforant path betwee n the two groups. BN52021 (5 muM), a PAF synaptosomal receptor antagonist, reduced LTP in the lateral path in the wild-type mice. However, neither BN5 2021, nor BN50730 (5 muM), a microsomal PAF-R antagonist, reduced LTP in th e lateral perforant path in the receptor-deficient mice. These data provide evidence that PAF-R-deficient mice are a useful model to study LTP in the dentate gyrus and support the notion that PAF actively participates in hipp ocampal synaptic plasticity.