Fig. 1. In situ hybridization shows the punctate distribution of poly(A) mRNAs throughout chick sympathetic neurons. Fixed neurons were hybridized with an oligo d(T) probe and fluorescent signals were developed using alkaline-phosphatase enzymatic amplification. Phase-contrast images (A,C,E) and fluorescent images (B,D,F) are shown for each field. Bright, punctate signals were detected along the length of the axons, along with bright staining of the cell bodies (B), which are also phase-dense because of the accumulation of HNP/Fast-Red-Texas-Red fluorescent material. Neurons treated with RNase prior to hybridization (D) or hybridized with sense oligo d(A) probes (F) show no signal in the axons and only trace levels of background staining in cell bodies. Scale bar, 20 µm.