NTRK1 and Alzheimer disease: Interestingly, the numbers of ChAT-containing neurons were stable in MCI and mild AD, while TrkA- and p75NTR-immunoreactive neurons were significantly decreased compared to NCI, indicating a phenotypic downregulation of receptors supporting CBF function rather than frank neuronal degeneration in MCI (Gilmor et al., 1999) (Figure 5).