Functional expression of P2Y purinoceptor in Xenopus oocyte injected with brain mRNA.

Xenopus oocytes injected with embryonic guinea-pig brain mRNA expressed functional P2Y purinoceptors. Extracellular ATP stimulated in a dose-dependent manner a delayed Ca(2+)-dependent Cl- current component. Analysis of the interactions of ATP with compounds that affect Ca2+ fluxes through the plasma membrane or Ca2+ release from internal stores indicates that ATP raises [Ca2+]i by a mechanism that involves activation of voltage-dependent Ca2+ channels, which leads to influx of extracellular Ca2+ into the cells, as well as release of Ca2+ from intracellular stores. Since this phenomenon was not found in control oocytes, it is suggested that brain mRNA encoded for a newly synthesized Ca(2+)-release process stimulated by purinoceptor activation. This mechanism could be largely involved in the short-term regulation of intracellular Ca2+ level involved in ATP neuromodulation functions.