Mu and delta opioid receptor activation inhibits omega-conotoxin-sensitive calcium channels in a voltage- and time-dependent mode in the human neuroblastoma cell line SH-SY5Y
Toselli, M.; Tosetti, P.; Taglietti, V.
Pflugers Archiv European Journal of Physiology 433(5): 587-596
1997
ISSN/ISBN: 0031-6768 PMID: 9049143 Document Number: 482254
Ca-2+ channel modulation by the mu opioid agonist (D-Ala-2, N-Me-Phe-4, Gly-5-ol)-enkephalin (DAGO) and the delta opiate agonists (D-Pen-2, D-Pen-5)-enkephalin (DPDPE) and (D-Ala-2, D-Leu-5)-enkephalin (DADLE) in cultured human neuroblastoma SH-SY5Y cells was investigated using the whole-cell variant of the patch-clamp technique. In SH-SY5Y cells, differentiated in vitro with retinoic acid, all agonists reversibly decreased high-voltage-activated, omega-conotoxin-sensitive Ba-2+ currents in a concentration-dependent way. Inhibition was maximal with a 1 mu-M concentration of opiate agonists (76% with DAGO and 63% with delta agonists, when measured at 0 mV) and was characterized by a clear slow down of Ba-2+ current activation at low test potentials. Both inhibition and slow down of activation were attenuated at more positive potentials, and could be partially relieved by strong conditioning depolarizations. Current suppression operated by both mu and delta agonists was prevented by pre-treatment of the cells with pertussis toxin. No sign of additivity was observed when delta agonists were applied to cells that were maximally activated by DAGO, suggesting that a common mechanism, involving the same type of modulating molecule, is responsible for Ca-2+ channel inhibition promoted by activation of mu and delta opioid receptors in SH-SY5Y cells.