Plasticity in the phenotypic expression of brain opioid receptors: differential response of forebrain and hindbrain cultures to chemical depolarization.

Potassium chloride at a depolarizing concentration has a differential effect on the expression of opioid receptors in aggregating neuronal cultures prepared from the rat forebrain or hindbrain. The mu-selective enkephalin analogue DAGO was used to indicate that the effect of potassium chloride is not uniform on all subtypes of opioid receptors. These results suggest for the first time that chemical depolarization may modulate the phenotypic expression of opioid receptors.