DYNORPHIN-B INHIBITS THYMIDINE INCORPORATION INTO DNA IN FETAL-RAT AND GUINEA-PIG BRAIN-CELL AGGREGATES

Numerous studies suggest that opioids have a modulatory role in the re gulation of neural cell proliferation (1). We have found that mu opioi d receptor agonists inhibit thymidine incorporation into DNA of neural cells in rat fetal brain cell aggregates (2). This inhibition is cult ure age-dependent. Moreover, morphine inhibited glial cell proliferati on in a concentration dependent manner (3). In contrast, U50488, a kap pa opioid receptor agonist, exerted either an inhibitory or stimulator y action on thymidine incorporation depending on the culture duration (4). Here we addressed the question of the effect of the endogenous ka ppa-selective opioid peptide, Dynorphin B, on thymidine incorporation in rat or guinea pig aggregates expressing more than 50% of mu (rat) o r kappa (guinea pig) receptors. In both cultures Dynorphin B inhibited DNA synthesis by 30-40%.