Role of pituitary adenylyl cyclase-activating polypeptide in intracellular calcium dynamics of neurons and satellite cells in rat superior cervical ganglia.

Pituitary adenylyl cyclase-activating polypeptide (PACAP) is a bioactive peptide with diverse effects in the nervous system. The present study investigated whether stimulation of PACAP receptors (PACAPRs) induces responses in neurons and satellite cells of the superior cervical ganglia (SCG), with special reference to intracellular Ca2+ ([Ca2+]i) changes. The expression of PACAPRs in SCG was detected by reverse transcription-PCR. PACAP type 1 receptor (PAC1R), vasoactive intestinal peptide receptor type (VPAC)1R, and VPAC2R transcripts were expressed in SCG, with PAC1R showing the highest levels. Confocal microscopy analysis revealed that PACAP38 and PACAP27 induced an increase in [Ca2+]i in SCG, first in satellite cells and subsequently in neurons. Neither extracellular Ca2+ removal nor Ca2+ channel blockade affected the PACAP38-induced increase in [Ca2+]i in satellite cells; however, this was partly inhibited in neurons. U73122 or xestospongin C treatment completely and partly abrogated [Ca2+]i changes in satellite cells and in neurons, respectively, whereas VPAC1R and VPAC2R agonists increased [Ca2+]i in satellite cells only. This is the first report demonstrating the expression of PACAPRs specifically, VPAC1 and VPAC2 in SCG and providing evidence for PACAP38-induced [Ca2+]i changes in both satellite cells and neurons via Ca2+ mobilization.

P2Y purinoceptors mediate ATP-induced changes in intracellular calcium and amylase release in acinar cells of mouse parotid glands.

Adenosine 5'-triphosphate (ATP) can act as an extracellular signal that regulates various cellular functions. The present study aimed to determine which purinoceptors play a role in ATP-induced changes in intracellular Ca(2+) ([Ca(2+)]i) and amylase secretion in mouse parotid glands. ATP induced a steep increase in [Ca(2+)]i in acinar cells. The removal of extracellular Ca(2+) or the use of Ca(2+) channel blockers slightly inhibited this increase. Inhibition of PLCγ by U73122 and of IP3 by xestospongin C did not completely block this increase. The purinoceptor antagonists suramin and reactive blue-2 strongly inhibited the ATP-induced changes in [Ca(2+)]i. 2-MeSATP induced a strong increase in [Ca(2+)]i, while Bz-ATP induced a small [Ca(2+)]i increase, and UTP and α,ß-MeATP had no effect. The potency order of ATP analogs (2-MeSATP > ATP >> UTP) suggested that P2Y1 and P2Y12 play a significant role in the cellular response to ATP. RT-PCR revealed that P2X2,4,7 and P2Y1,2,10,12,14 were expressed in acinar cells. Ca(2+)-dependent exocytotic secretion of amylase was detected in parotid glands. These findings indicated that ATP activates P2Y receptors more than P2X receptors at low concentrations. Thus, P2Y receptors were found to be the main receptors involved in Ca(2+)-related cell homeostasis and amylase secretion in mouse parotid glands.