Opioids acting through delta receptors elicit a transient increase in the intracellular free calcium concentration in dorsal root ganglion-neuroblastoma hybrid ND8-47 cells.
The neuronal cell line ND8-47 (neuroblastoma x dorsal root ganglion neuron hybrid) expressed opioid delta-type receptors. We report opioid-induced changes in cytosolic intracellular free calcium ([Ca++]i) in differentiated ND8-47 cells. Delta-opioid receptor agonists induced a transient (< 2 min) increase in [Ca++]i in a concentration-dependent fashion with the potency order: [D-Ser2,Leu5]enkephalin-Thr (DSLET) > or = deltorphin II > [D-Pen2,5] enkephalin. Their effects were blocked by naloxone (IC50 = 20 nM) and naltrindole (IC50 = 2.5 nM). Selective mu and kappa receptor agonists had no effect on [Ca++]i. The subtype specific delta receptor antagonists, 7-benzylidene naltrexone (delta-1) and naltriben (delta-2), were used to characterize further the subtype of delta receptors mediated by this response. Naltriben was more potent than 7-benzylidene naltrexone in antagonizing the DSLET-induced increase in [Ca++]i. The increase in [Ca++]i induced by DSLET was blocked by nifedipine (1 microM) or verapamil (1 microM), and was not observed in the absence of external calcium. Changes in [Ca++]i also were measured in single ND8-47 cells. The percentage of cells responding to DSLET (1 microM), deltorphin-II (1 microM) and [D-Pen2,5]enkephalin (1 microM) were 86, 84 and 37%, respectively. The results suggest that an increase in [Ca++]i induced by opioids is mediated through opioid delta receptors which can activate dihydropyridine-sensitive Ca++ channels.
Tang
T
T
Department of Pharmacology, Uniformed Services University of Health Sciences, Bethesda, Maryland.
Kiang
J G
JG
Cox
B M
BM
D000700:Analgesics / Q000494:pharmacology; D000814:Aniline Compounds; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D004745:Enkephalins / Q000494:pharmacology; D005434:Flow Cytometry; D005453:Fluorescence; D016257:Fura-2; D005727:Ganglia, Spinal / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D006822:Hybrid Cells; D007424:Intracellular Fluid / Q000378:metabolism; D007700:Kinetics; D007834:Lasers; D051379:Mice; D009294:Narcotics / Q000494:pharmacology*; D009447:Neuroblastoma; D009475:Neurons, Afferent / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017465:Receptors, Opioid, delta / Q000187:drug effects* / Q000502:physiology*; D014407:Tumor Cells, Cultured; D014966:Xanthenes
D000700:Analgesics; D000814:Aniline Compounds; D004745:Enkephalins; D009294:Narcotics; D017465:Receptors, Opioid, delta; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium; D016257:Fura-2