P2RX7 and Alzheimer disease: Moreover, the Aβ25–35 fragment evokes intracellular Ca2+ concentration changes via connexin hemichannel opening and purinergic receptor activation in astrocytes, whose exposure to Aβ25–35 induces both a Ca2+-independent and Ca2+-dependent glutamate release in the brain of the hAPPJ20 AD mouse model [150].