Effects of ohmefentanyl stereoisomers on phosphorylation of cAMP- response element binding protein in cultured rat hippocampal neurons.

Aim: To define the effects and signal pathways of ohmefentanyl stereoisomers [(-)-cis-(3R,4S,2'R) OMF (F9202), (+)-cis-(3R,4S,2'S) OMF (F9204), and (-)-cis-(3S,4S,2'R) OMF (F9203)] on the phosphorylation of cAMP-response element binding protein (CREB) in cultured rat hippocampal neurons.

Methods: The effects of the three OMF stereoisomers and morphine (Mor) on cAMP accumulation and CREB phosphorylation were monitored by radioimmunoassay and Western blot analysis, respectively.

Results: The three OMF stereoisomers and Mor could all partially inhibit forskolin-stimulated (25 micromol/L, 15 min) cAMP accumulation in a dose-dependent manner and this effect could be reversed by naloxone. F9202, F9204, and Mor could significantly increase CREB phosphorylation from 2.88 to 3.59 folds over control levels after 30-min exposure. This effect was reversed by naloxone, but F9203 failed to increase CREB phosphorylation. KN-62 and staurosporine significantly blocked the opioids- induced CREB phosphorylation, while H-89 and PD 98059 had no effect on the actions.

Conclusion: Mor, F9202, and F9204, which could induce psychological dependence affected via the micro-opioid receptor, stimulated intracellular signal pathways involving Ca2+/calmodulin-dependent protein kinases (CCDPK) and protein kinase C (PKC) pathways, which in turn initiated CREB phosphorylation. F9203, which could not induce dependence, had no effect on CREB phosphorylation in hippocampal neurons. The increased CREB phosphorylation in hippocampal neurons may play a role in opioids dependence.