Expression of p75NTR and TH mRNAs in response to different spatial sources of NGF. The upper panels are photographs of
autoradiographs produced by hybridizing Northern blots with radiolabeled probes specific for each mRNA. The lower panels are photographs
of the original agarose gels with the samples electrophoresed in the presence of ethidium bromide to demonstrate that equivalent amounts
of total RNA were loaded in each lane. (A) Expression of p75NTR (P75) and tyrosine hydroxylase (TH) mRNAs in sister cultures of
neonatal sympathetic neurons cultured in the presence of 10 ng/ml NGF for 7 days, followed by distal (D) addition of 200 ng/ml NGF
for 12, 24, or 48 hr. The control (Cont.) was maintained in 10 ng/ml NGF for the additional time period. (B) Expression of p75NTR and
TH mRNAs in sister cultures of sympathetic neurons cultured in the presence of 10 ng/ml NGF for 7 days, followed by global addition
of 200 ng/ml NGF for 24 or 48 hr. The control (Cont.) was maintained in 10 ng/ml NGF for the additional time period. The blot labeled
P75 was probed for both mRNAs, with the upper band being p75NTR mRNA and the lower band, TH mRNA. (C) Expression of p75NTR
and TH mRNAs in sister cultures of sympathetic neurons cultured in the presence of 10 ng/ml NGF for 7 days, followed by application
of 200 ng/ml NGF for 48 hr distally (D), globally (G), or in the central compartments (C).