Extracellular
nucleotides modulate synaptic transmission and neuronal communication by activating purinergic 2 (P2) (
nucleotide) receptors. Here, we assessed changes in the regulation by
nucleotides and their receptors of an important physiological response - release and uptake of
catecholamines - that accompanies sympathoadrenal neuronal differentiation.
Nerve growth factor (
NGF)-promoted differentiation of
pheochromocytoma 12 (PC12) cells enhanced the ability of the non-hydrolyzable
ATP analog,
ATPgammaS, to stimulate
catecholamine (
norepinephrine, NE) release and this enhancement occurred without a significant alteration in NE uptake. In addition to
ATPgammaS,
2-MeSATP and alphabetaMeATP, P2X receptor-selective agonists, caused greater NE release from
NGF-differentiated than from undifferentiated PC12 cells.
NGF-differentiated PC12 cells had altered
mRNA expression of several P2Y and P2X receptors but
protein expression was only increased for P2X, in particular P2X(1-4,) receptors and P2X, but not P2Y, receptor inhibitors blunted the
NGF-promoted enhancement in
nucleotide-regulated
catecholamine release. Surprisingly,
siRNA directed against P2X(2), the receptor with the highest expression, failed to alter NE release by
ATPgammaS. These findings indicate that sympathetic neuronal differentiation by
NGF increases both the expression of P2X receptor sub-types and their regulation of
catecholamine release.
NGF-promoted increased expression of P2X receptors thus appears to be a physiologically important response that characterizes sympathetic neuronal differentiation.