In situ hybridization histochemistry as a tool to study gene expression and its regulation in the central nervous...

The recent application of in situ hybridization histochemistry to neuroanatomy, neuroendocrinology, and neuropharmacology has permitted explorations into the regulation of gene expression in the central nervous system (CNS) at the level of single neurons. Although cDNAs were the first probes to be used in hybridization studies, cRNAs and synthetic oligonucleotides have been recently employed because of the many advantages these single-stranded probes offer compared to the cDNAs. Using synthetic oligonucleotides, we described the distribution of the calmodulin mRNA and the regulation of proenkephalin mRNA in the rat brain. The results reported show the specificity of the hybridization and that the levels of calmodulin mRNA are more abundant in the cerebral cortex than in the striatum. Furthermore, we demonstrated that the administration of 6-hydroxydopamine in early postnatal life induces an increase in the expression of striatal proenkephalin mRNA measured at postnatal day 32.