PPP1R9B and viral infectious disease: To test whether 5-HT1aR-mediated synaptogenesis depends on CREB activation, we infused LV-CREB133-GFP or LV-VP16-CREB-GFP into the hippocampal DG of mice by microinjection, and at 21 d after virus infection, we measured expressions of synapsin and spinophilin, two well-characterized synaptic proteins24, 25.