In various manipulations of the neurotrophins it has been noted that molecular markers for proprioceptive axons such as PV or calcitonin gene-related peptide for nerve growth factor–responsive axons are compromised (Ringstedt et al. 1997; Patel et al. 2000), thus PV immunostaining in Bax/NT-3 double KOs cannot reveal the extent of proprioceptive axons in the periphery.