DEPOLARIZATION REGULATES SELECTIVELY THE EXPRESSION OF DIFFERENT OPIOID RECEPTORS - A DECREASED NUMBER OF KAPPA-RECEPTORS IN CHRONICALLY ACTIVATED GUINEA-PIG BRAIN-CELL CULTURES

Previous studies about the differential effect of chronic membrane depolarization on the expression of μ and δ opioid receptors prompted us to investigate whether the same treatment regulates also the expression of κ opioid receptors. Embryonic guinea pig brain cells that exhibit in culture a high density of κ receptors were treated for different time periods with potassium chloride, and the number of these receptors was determined with the universal opioid ligand [3H]diprenorphine. In a second set of experiments the cultures were treated with the sodium channel activator veratridine and opioid receptors were determined with the selective κ ligand [3H]U69,593. The results indicate that chronic membrane depolarization (for 3 or 6 days) decreases significantly the number of κ receptors, with no effect on the affinity of the ligands. Taken together with our previous reports, it is suggested that neuronal activation has a selective and possibly opposite regulatory role on the expression of the 3 opioid receptors. © 1990.