Neuroblastoma-glioma hybrid cells contain clonidine-displacing substance

Clonidine-displacing substance (CDS) isolated from bovine brain potently inhibits clonidine binding and elicits contraction of gastric smooth muscle. We sought to determine if CDS was contained in neuron-like clonal cells (neuroblastoma X glioma hybrid NG108-15). Extracts were prepared from osmotically shocked P2 fractions of NG108-15 cells. One unit of CDS, as defined by a [3H]p-aminoclonidine radioreceptor assay using bovine frontal cortex membranes, was obtained from each 1.3 million cells processed. CDS isolated from NG108-15 cells was biologically active on gastric smooth muscle. NG108-15 cells may serve as a model system for the study of this endogenous clonidine-like ligand.