GLIAL EXPRESSION OF THE PROENKEPHALIN GENE IN SLICE CULTURES OF THE SUBVENTRICULAR ZONE

The proenkephalin (PEnk) gene is expressed in rats in the neocortical subventricular zone (nSVZ) of the lateral ventricle during the first p ostnatal week, when precursors of astro- and oligoglial cells of the r at neocortex proliferate in this area. To study the expression of the gene in the glial precursors, slices containing the nSVZ were prepared from the brains of newborn and 7-day-old rats. After 1-5 d of cultiva tion, numerous cells that expressed PEnk mRNA were found in the nSVZ w ith in situ hybridization. Some of these cells coexpressed the glial f ibrillary acidic protein (GFAP), indicating that they were of astrogli al origin. Activation of protein kinase A with 8Br.cAMP strongly enhan ced the number of cells that expressed the PEnk gene in slices prepare d from the brains of newborn or 7-d-old rats. Also pituitary adenylate cyclase activating polypeptide (PACAP) proved to be effective. After stimulation with 8Br.cAMP or PACAP-38, PEnk mRNA-containing cells were found in the subventricular zone as well as in the adjacent area thro ugh which glial cells migrate on their way to the neocortex. It has th erefore been concluded that protein kinase A may regulate the expressi on of the PEnk gene expression in glial precursors in the nSVZ.