TGFα mRNA levels in the ventral horn of the cervical spinal cord. A, Autoradiogram of TGFα ribonuclease protection assay (4 d exposure, 5 μg/lane total RNA).TGFα, Undigested TGFα cRNA probe;Cyclo, undigested cyclophilin cRNA probe;Digested probes, digested TGFα and cyclophilin cRNA probes; E15 csc, 5 μg of total RNA from the ventral horn of an E15 rat cervical spinal cord. B, Densitometric analysis of TGFα mRNA signals. Eachpoint represents five (E12–E21), four (P2–P6), and three (P14–P60) animals. Mean ± SD; n = 3–4.