REGULATION OF KAPPA-OPIOID RECEPTOR MESSENGER-RNA LEVEL BY CYCLIC-AMPAND GROWTH-FACTORS IN CULTURED RAT GLIAL-CELLS

The mRNA of the kappa-opioid receptor (KOR) has been found recently in cultured astrocytes and in microglia, By using RT-PCR and Southern hy bridization, we confirmed these observations and, in addition, we obse rved that KOR mRNA was expressed in oligodendrocytes and in the precur sors of astrocytes and oligodendrocytes. KOR mRNA level was the highes t in the immature astrocytes and decreased with their maturation. Very few data are available on the regulation of KOR level by extracellula r signals. Therefore, we examined the effect of three growth factors k nown to be present in the adult brain, basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF-BB) and leukemia inhibito ry factor (LIF) and of two cyclic AMP (cAMP) generating systems, the c AMP analog, 8-(4-chlorophenylthio)-cAMP and forskolin, on this level. It was found that in astrocytes, KOR mRNA level decreased dramatically under the effect of cAMP and less under the effect of bFGF while it d id not change significantly after LIF treatment. In oligodendrocytes, it also decreased with cAMP, but increased under the effect of bFGF an d PDGF-BB. In microglia, a decrease was observed with cAMP and lipopol ysaccharides (LPS), the most used activators of macrophages. These res ults shed new evidence on the expression of opioid receptor mRNA in th e glial cells of the rat CNS. The regulation of KOR mRNA level under t he effect of extracellular signals suggests that opioids take part in dynamic processes in glial cells, possibly related to glial-neuron com munication. (C) 1998 Elsevier Science B.V.