Modulation of thymidine incorporation by κ-opioid ligands in rat spinal cord-dorsal root ganglion co-cultures

β-Endorphin, met-enkephalin and several μ-selective opioid agonists were shown to decrease thymidine incorporation into DNA in various neural cell cultures. We now report that the κ-selective opioid agonists U50488, U69593 and MR2034 modulate [³H]thymidine incorporation into DNA in rat spinal cord-dorsal root ganglion co-cultures. U50488 at 10 μM increased by 60% thymidine incorporation in 6-day-old cultures. The thymidine incorporation induced by U50488 was blocked by the κ-selective antagonist nor-binaltorphimine, as well as by pertussis toxin and LiCl U50488 treatment stimulated phosphatidylinositol turnover by three-fold compared with untreated controls. These findings suggest that κ-opioid agonists modulate DNA synthesis in spinal cord-dorsal root ganglion co-cultures through a mechanism which involves pertussis toxin-sensitive GTP-binding proteins, as well as activation of phosphatidylinositol turnover.