NEUROTENSIN TRANSCRIPTION IS OPPOSITELY REGULATED DURING DEVELOPMENT AND REGENERATION

OUR previous work demonstrated that neurotensin mRNA expression was tr ansiently up-regulated during development in the hypoglossal motoneuro ne. The present study was carried out to examine how neurotensin mRNA expression changes during nerve regeneration. Following either unilate ral resection or crushing of the hypoglossal nerve, mRNA expression wa s detected by non-radioactive in situ hybridization histochemistry usi ng an alkaline phosphatase-labelled oligonucleotide probe. A reduction in neurotensin mRNA was observed on the operated side after the nerve injury. It took around 2 months for NT mRNA levels to return to norma l. Similar down-regulation was observed following crushing, but recove ry was more rapid than that observed with sectioning, probably due to the extent of nerve damage. This finding indicates that neurotensin tr anscription is up-regulated during development but, on the contrary, d own-regulated during regeneration.