(A) Calcineurin activity is required for NGF-dependent internalization of TrkA receptors. Cell surface biotinylation and TrkA immunoblotting shows that NGF-dependent TrkA endocytosis is reduced by calcineurin inhibiton. (B) Densitometric quantification of internalized TrkA, **p<0.01, n=6. (C) TrkA endocytosis is dependent on PLC-γ activity. PLC-γ inhibitor (U73122) decreases NGF-dependent TrkA endocytosis. (D) Densitometric quantification of internalized TrkA, *p<0.05 and **p<0.01, n=4. In (A) and (C), supernatants were probed for p85 for normalization.