Differentiation‐associated decrease in muscarinic receptor sensitivity in human neuroblastoma cells

Abstract

Muscarinic receptor‐linked increases in intracellular free Ca²⁺ as measured with quin‐2 and Ca²⁺ release from monolayers of cells have been measured in the human neuroblastoma cell line SH‐SY5Y. Induction of differentiation with the phorbol ester 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) leads to a decrease in the sensitivity of the cells to low concentrations of agonists with respect to the induced increase in cytosolic free Ca²⁺ and stimulation of Ca²⁺ efflux. No decrease in agonist binding affinity was observed when the displacement of a labelled antagonist, ³H‐NMS, by a non‐labelled agonist was studied.