The aim of this proposal is to study the blood-cerebrospinal fluid barrier (BCSFB) located at the choroid plexus (CP) level. Being the CP epithelial cells responsible for both the blood-CSF barrier formation and for the CSF production, we hypothesize that CP cells changes during aging and in Alzheimer disease (AD) may alter brain fluidics and the drainage pathways. To test this hypothesis, we are performing Patch-seq analysis, a technique that combines whole-cell patch clamp recording and scRNA-seq to draw the profile of single CP epithelial cells from wild type (WT) and AD mouse models.