Indeed, GABAergic input promotes the differentiation of amplifying intermediate progenitor cells. Learning and memory forma MG132 tion rely Inhibitors,Modulators,Libraries on the experience related modification of synap tic structures Inhibitors,Modulators,Libraries in the hippocampus and on the induction of LTP, an activity dependent change in the synaptic strength. It has already been shown that the in vivo induction of LTP at MPP inputs to the DG promotes neurogenesis, Inhibitors,Modulators,Libraries and conditional ablation of adult neurogenesis im pairs LTP at MPP synapses, suggesting that these two processes are functionally linked. Whether the effect of Smad3 on neurogenesis might represent a link between these processes or if they are regulated in an independent Inhibitors,Modulators,Libraries manner will require further study.
Furthermore, although Smad3 deficiency does not alter the number of mature granule neurons generated during embryonic develop ment, we could not exclude a developmental alteration, and that Inhibitors,Modulators,Libraries glial cells deficient in Smad3 could also influence the observed effects. However, Smad3 seems to be a major contributor to both neurogenesis and LTP induction in the adult DG, these being two forms of hippocampal brain plasticity related to learning and memory. Physiological conditions such as external aversive or enriching experiences, including stress or learning, may in fluence both neurogenesis and LTP. Cycling inter mediate progenitor cells have been seen to be the target of neurogenic external stimuli, such as running. In this sense, Smad3 may participate in the physiological events regulated by neurogenesis. Indeed activin modulates anxiety and depression responses in mice.
On the other hand, different brain pathologies alter AHN, such as epilepsy, stroke, inflammation or neurodegeneration, and different forms selleck inhibitor of dementia and alterations in hippo campal neurogenesis are associated with Parkinsons and Alzheimers disease. Smad3 deficient mice represent an interesting model to study parkinsonism due to the ef fects on nigrostriatal dopaminergic neurodegeneration and synuclein aggregation, where overexpression of synuclein may also play a role on hippocampal neurogen esis. Further studies will clarify whether this effect of Smad3 on hippocampal LTP and neurogenesis may be re lated to pathological events. Conclusions We show here for the first time that endogenous Smad3 signaling is a major contributor to neurogenesis and LTP in the adult DG, highlighting its role in the intrinsic mechanisms that govern neuronal precursors and hippo campal plasticity. Methods RNA In situ hybridization All steps for RNA in situ hybridization were performed in a RNase free environment, as described by Young and Mezey. To generate DIG labeled antisense and sense riboprobes, a cDNA fragment of Smad3 was generated by PCR and cloned into the XhoIBamHI sites of pCRII.