Autoradiographic localization of somatostatin mRNA in the adult rat lower brainstem: observation by the double illumination technique.

Using in situ hybridization histochemistry and observation with a double (dark and bright) illumination apparatus, the precise localization of preprosomatostatin mRNA was studied in the adult rat lower brainstem and cerebellum. It has previously been hard to localize the somatostatin precursor gene in the adult rat brainstem, because the level of expression is low or undetectable in some brain areas in adulthood, in contrast to the high levels in the neonatal period. The present study in adult rats showed the clear localization of this mRNA in the same areas where it is found in the perinatal period. The results showed that somatostatin neurons in such areas continue the minimal production of the precursor gene even at the adult stage.