RT-PCR analysis to detect: (A) alternatively spliced trkA mRNA isoforms in HMC-1 cells, K-562 cells, and fetal monkey brain tissue, (B) the expression of truncated isoforms of trkB and trkC in human substanta nigra and HMC-1 cells, and (C) the expression of p75 mRNA transcripts in HMC-1 cells, Hs294T cells, and fetal monkey brain tissue. The cDNAs were synthesized from total RNA or poly A+ mRNA from each of the indicated cells or tissues by reverse transcriptase and amplified by PCR using primers C and D for trkA in (A), and primers E and F for trkB.T1 in (B), and primers G and H for truncated trkC in (B), and primers R and S for p75 in (C). The PCR products were analyzed on a 5% nondenaturing polyacrylamide gel in (A). The identity of PCR products in (B) and (C) was confirmed by Southern blot analysis using ³²P-labeled monkey trkB and trkC cDNA probes in (B), and a monkey p75 cDNA probe in (C).