Effects of ATP on intracellular calcium dynamics of neurons and satellite cells in rat superior cervical ganglia

Adenosine 5'-triphosphate (ATP) which is released from neuronal and non-neuronal tissues interacts with cell surface receptors to produce a broad range of physiological responses. The present study addressed the issue of whether the cells of the superior cervical ganglia (SCG) respond to ATP. To this end, the dynamics of the intracellular calcium ion concentration ([Ca2+]i) of neurons and satellite cells in intact SCG was analyzed by laser scanning confocal microscopy. ATP produced an increase of [Ca2+]i in both neurons and satellite cells; initially, ATP elicited [Ca2+]i increase in satellite cells and, subsequently, a [Ca2+]i change in neurons was observed. P1 purinoceptor agonists had no effect on this process, but P2 purinoceptor agonists induced [Ca2+]i increase and suramin totally inhibited ATP-induced [Ca2+]i dynamics in both neurons and satellite cells. In satellite cells, Ca2+ channel blockers and the removal of extracellular Ca2+, but not thapsigargin pretreatment, abolished ATP-induced [Ca2+]i dynamics. In contrast, thapsigargin pretreatment abolished ATP-induced [Ca2+]i dynamics in neurons. Reactive blue-2 inhibited the ATP-induced reaction on neurons alone. Uridine 5'-triphosphate caused a [Ca2+]i increase in neurons and alpha,beta-methylene ATP caused a [Ca2+]i increase in satellite cells. We concluded that neurons respond to extracellular ATP mainly via P2Y purinoceptors and that satellite cells respond via P2X purinoceptors.