Characterization of an adenylate cyclase-linked serotonin (5-HT1) receptor in a neuroblastoma X brain explant hybrid cell line (NCB-20).

Clonal cell line NCB-20 (a hybrid of mouse neuroblastoma N18TG2 and Chinese hamster 18-day embryonic brain explant) expressed both high- (KD 180 nM) and low-affinity (greater than 3000 nM) binding sites for [3H]serotonin (5-HT) which were absent from the parent neuroblastoma. The low-affinity binding site was eliminated by 1 microM spiperone. The order of drug potency for inhibition of high-affinity [3H]5-HT binding was consistent with a 5-HT1 receptor (5,6 - dihydroxytryptamine = 5-HT = methysergide = 5-methoxytryptamine greater than cyproheptadine = clozapine = mianserin greater than spiperone greater than dopamine = morphine = ketanserin = norepinephrine). [3H]5-HT binding was inhibited by guanine nucleotides (e.g., GTP and Gpp(NH)p), whereas antagonist binding was not; ascorbate was also inhibitory. A 30-min exposure of cells to 1-2 microM 5-HT or other agonists produced a three- to fivefold stimulation of cyclic AMP levels. The order of potency for 5-HT agonist stimulation of basal cyclic AMP levels and 5-HT antagonist reversal of agonist-stimulated levels was the same as the order of drug potency for inhibition of high-affinity [3H]5-HT binding, suggesting linkage of the 5-HT1 receptor to adenylate cyclase in NCB-20 cells.