Abstract
Facial vibrissae, commonly known as whiskers, are the main sensitive tactile system in rodents. Whisker stimulation triggers neuronal activity that promotes neural plasticity in the barrel cortex (BC) and helps create spatial maps in the adult hippocampus. Moreover, activity-dependent inputs and calcium homeostasis modulate adult neurogenesis. Therefore, the neuronal activity of the BC possibly regulates hippocampal functions and neurogenesis. To assess whether tactile information from facial whiskers may modulate hippocampal functions and neurogenesis, we permanently eliminated whiskers in CD1 male mice and analyzed the effects in cellular composition, molecular expression and memory processing in the adult hippocampus. Our data indicated that the permanent deprivation of whiskers reduced in 4-fold the density of c-Fos+ cells (a calcium-dependent immediate early gene) in cornu ammonis subfields (CA1, CA2 and CA3) and 4.5-fold the dentate gyrus (DG). A significant reduction in the expression of calcium-binding proteincalbindin-D28k was also observed in granule cells of the DG. Notably, these changes coincided with an increase in apoptosis and a decrease in the proliferation of neural precursor cells in the DG, which ultimately reduced the number of Bromodeoxyuridine (BrdU)+NeuN+ mature neurons generated after whisker elimination. These abnormalities in the hippocampus were associated with a significant impairment of spatial memory and navigation skills. This is the first evidence indicating that tactile inputs from vibrissal follicles strongly modify the expression of c-Fos and calbindin in the DG, disrupt different aspects of hippocampal neurogenesis, and support the notion that spatial memory and navigation skills strongly require tactile information in the hippocampus.
Highlights
Facial vibrissae, referred to as whiskers, are the main sensitive tactile system in rodents
Whisker Fulguration Decreases Cytochrome C Oxidase and c-Fos-Expressing Cells in Barrel Cortex c-Fos protein is coded by a calcium-dependent immediate early gene that is used as a marker of neuronal activity (Herrera and Robertson, 1996)
To determine changes in the neuronal activity that occur after permanent whisker deprivation (WD), we fulgurated whiskers in postnatal 60 (P60) mice and analyzed the expression of cytochrome oxidase and c-Fos (n = 5 mice per group)
Summary
Referred to as whiskers, are the main sensitive tactile system in rodents. Some studies have shown that the whisker tactile information linked to fine discrimination increases the spiking rate in the CA1 hippocampal region (Pereira et al, 2007; Itskov et al, 2011). Whisker elimination during early brain development reduces the activity of CA3 neurons, which induces CA3-CA1 synaptic facilitation (Milshtein-Parush et al, 2017). This evidence indicates that many of the tactile inputs from the vibrissal system are processed in the hippocampus, and this tactile information seems to play an important role in the creation of spatial maps (Pereira et al, 2007)
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