Opiate receptors in highly purified neuronal cell populations isolated in bulk from embryonic chick brain

Abstract

A bulk isolation procedure was used to obtain neuronal and non-neuronal cell populations from embryonic chick brain. The procedure utilizes the differences in cell-substrate adhesiveness of the two populations and the ability of the former to form homotypic aggregates in the presence of intermittent mechanical agitation. [ 3H]-Thymidine incorporation, semi-quantification of S-100 protein, and recycling of radioactively labelled putative non-neuronal cells through the isolation procedure indicate that the neuronal fraction contained less than 1% of non-neuronal cells. The binding of [ 3H]-naloxone to the isolated neuronal cells was characterized. These cells were found to have opiate receptors which are very similar to those found in adult rat brain with respect to stereospecificity of [ 3H]-naloxone binding, the ability of several opiate agonists and antagonists of varying analgesic activity to displace bound [ 3H]-naloxone, and the differential response of these drugs to Na +. Isolated non-neuronal cells, in contrast, had no specific opiate binding activity. Total binding activity of both populations of cells was greatly increased after 24 hr in culture. However, while a major portion of the activity of the neuronal cells was of the specific type, all of the activity in the non-neuronal cells remained nonspecific.