Microglial cells are the immunocompetent cells of the CNS, which are known
to exist in several activation states. Here we investigated the impact of m
icroglial activation on the P2 receptor-mediated intracellular calcium ([Ca
2+]ii) signaling by means of fluo-3 based Ca2+-imaging. Cultured mouse micr
oglial cells were treated with either astrocyte-conditioned medium to induc
e a ramified morphology or LPS to shift the cells toward the fully activate
d stage. The extracellular application of ATP (100 mu M) induced a [Ca2+],
elevation in 85% of both untreated and ramified microglial cells, whereas o
nly 50% of the LPS-activated cells responded to the stimulus. To characteri
se the pharmacological profile of microglial P2 receptors we investigated t
he effects of various P2 agonists on [Ca2+](i) in cultured microglial cells
. Untreated and ramified microglial cells demonstrated a very similar sensi
tivity to the different P2 agonists. In contrast, in LPS-activated microgli
a, a sharp decrease of responses to P2 agonist stimulation was seen. This i
ndicates that microglial activation influences the capability of microglial
cells to generate [Ca2+]i signals upon P2 receptor activation. (C) 2000 El
sevier Science B.V. All rights reserved.