INVERSION OF CA2-CELLS FROM PERTUSSIS TOXIN PRETREATMENT( CURRENT MODULATION DURING RECOVERY OF NEUROBLASTOMA)

Human neuroblastoma cells (SH-SY5Y) differentiated by retinoic acid ex hibited high threshold-activated N-type Ca2+ Currents, which were larg ely inhibited by the two enkephalins, DAGO and DPDPE, as well as by do pamine and somatostatin. The inhibitory effects were fully abolished a fter pretreatment of cells with pertussis toxin. After washing out the toxin, the inhibitory effects re-established with a time constant of about 16 h. The recovery of Ca2+ current inhibition was similar for al l tested agonists. Unexpectedly, we observed a neurotransmitter-induce d stimulation of Ca2+ currents in approximately 10% of all investigate d cells during the recovery phase. Such a stimulatory effect by otherw ise inhibitory receptors was never seen in control cells. It did also not occur when exogenous purified G-proteins of the G(i) family were r econstituted via the patch pipette, suggesting that additional mechani sms may play a role in the appearance of stimulatory effects during th e recovery phase after pertussis toxin pretreatment.