1. The properties of individual excitatory synaptic sites onto adult CAl hippocampal neurons were investigated using paired pulse minimal stimulation and low noise whole-cell recordings. -62% coefficient of variation between sites) and intrinsic variation over time (-36%).Paired pulse plasticity occurred primarily from alterations in the release probabilities but a few ensembles also showed small changes in site amplitude. Initial release probability correlated negatively with the degree of paired pulse potentiation. Whilst it was possible to use simple assumptions regarding site homogeneity (such as required for a binomial process) for 48% (12 out of 25) of the data sets, the Bayesian analysis was necessary to reveal the complex changes and heterogeneity that occurred in the other 52% of the data sets. The Bayesian site analysis robustly indicated the presence of considerable site heterogeneity, significant intrinsic site variation over time and changes in parameters at individual synaptic sites with plasticity.

In vertebrates, memory-relevant synaptic plasticity involves postsynaptic rearrangements of glutamate receptors. In contrast, previous work indicates that Drosophila and other invertebrates store memories using presynaptic plasticity of cholinergic synapses. Here, we provide evidence for postsynaptic plasticity at cholinergic output synapses from the Drosophila mushroom bodies (MBs). We find that the nicotinic acetylcholine receptor (nAChR) subunit α5 is required within specific MB output neurons (MBONs) for appetitive memory induction, but is dispensable for aversive memories. In addition, nAChR α2 subunits mediate memory expression downstream of α5 and the postsynaptic scaffold protein Dlg. We show that postsynaptic plasticity traces can be induced independently of the presynapse, and that in vivo dynamics of α2 nAChR subunits are changed both in the context of associative and non-associative memory formation, underlying different plasticity rules. Therefore, regardless of neurotransmitter identity, key principles of postsynaptic plasticity support memory storage across phyla.

32The interaction between the bone and immune cells plays a crucial role in bone pathologies 33 such as disturbed fracture healing. After a trauma, the initially formed fracture hematoma in 34 the fracture gap contains all important components (immune/stem cells, mediators) to directly 35 induce bone regeneration and is therefore of great importance but most susceptible to negative 36 influences. Thus, reliable in vitro models are needed to study the underlying mechanisms and 37 to predict the efficiency of novel therapeutic approaches. Since common bioengineering 38 approaches exclude the immune component, we introduce an in vitro 3D fracture gap model 39 which combines scaffold-free bone-like constructs with a fracture hematoma model consisting 40 of human peripheral blood (immune cells) and bone marrow-derived mesenchymal stromal 41 cells. Our in vitro 3D fracture gap model provides all osteogenic cues to induce the initial bone 42 healing processes, which were further promoted by applying the osteoinductive deferoxamine 43 (DFO). Thus, we were able to distinctly mimic processes of the initial fracture phase and 44 demonstrated the importance of including the crosstalk between bone and immune cells. 45 46 47 Key words: bone; fracture; fracture hematoma; immune cells; in vitro model the tissue (Fig. 2a). Interestingly, SFBCs which showed a higher amount of negative stained 130 area, showed a more pronounced layer-like structure while the layers itself were strongly 131 mineralized at the borders ( Fig. 2a; lower row). Negative controls were cultivated without 132 osteogenic medium (Fig. 2b). In addition, we observed the expression of collagen type I (Col 133 I) and alkaline phosphatase (ALP), which are typical markers for osteogenic processes, while 134 no Col II, a typical marker of chondrogenesis, was found ( Fig. 2c). 135