Figure 1. p75^NTR plays multiple roles in development.

(A) Timeline of mouse development indicating the expression of p75^NTR, TrkA and ChAT. NGF and BDNF appear to play complementary roles in inducing the differentiation of septal and magnocellular cBF neurons, respectively. TrkA and TrkB also regulate axonal growth and ChAT expression but not cBF neuron survival. The age at which TrkB and TrkC expression is induced in cBF neurons is unclear. (B) Comparison of the number of cBF neurons in ‘wild-type’ (WT; p75^fl/fl; black), and mice lacking p75^NTR from either E18 (via TrkA-cre; MGI:4360700; >95% recombination) or P4 (via ChAT-cre). ChAT-positive cells were counted in every third section (as described in [125]) in the MS, VDB and HDB of P30 animals. As both knockout strains lack p75^NTR expression during the postnatal period, which reduces programmed cell death (red bracket), the reduced cBF neuronal number in TrkA-cre p75^NTR-deficient mice compared with ChAT-cre p75^NTR-deficient animals indicates a role for p75^NTR in cBF neuronal survival or differentiation between E18 and P4 (blue bracket compared with green bracket). n=3 mice per genotype. *P<0.05, **P<0.01, one-way ANOVA.