P. Friederich et al., INVERSION OF CA2-CELLS FROM PERTUSSIS TOXIN PRETREATMENT( CURRENT MODULATION DURING RECOVERY OF NEUROBLASTOMA), FEBS letters, 334(3), 1993, pp. 322-326
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.