The cellular localization of preprotachykinin A messenger RNA in the bovine nervous system

The cellular distribution of preprotachykinin A messenger RNA in the bovine nervous system was investigated by in situ hybridization and its tissue distribution by Northern and dot blotting. The latter results were compared with the levels of substance P-like immunoreactivity as determined by radio-immunoassay. The highest levels of preprotachykinin A messenger RNA were found in striatum and trigeminal ganglion, medium levels in retina and lower levels in hypothalamus, spinal cord, pituitary gland and adrenal medulla. The cellular localization of preprotachykinin A messenger RNA was obtained in striatum and trigeminal ganglion using either single-stranded DNA or complementary RNA probes labelled with 32P, 35S or 3H. Specific labelling of small trigeminal ganglion neurones and of medium-sized striatal nerve cells was observed with probes in the anti-messenger RNA sense orientation. Only background labelling was obtained with probes in the messenger RNA sense orientation. The technique was further validated by the demonstration that the same cells in the trigeminal ganglion were labelled by both in situ hybridization and immunohistochemistry. The present findings allow an unambiguous identification of the cellular sites of synthesis of preprotachykinin A messenger RNA; in situ hybridization should also prove a useful technique for investigating the regulation of neuropeptide biosynthesis at the cellular level.