P2RX7 and major depressive disorder: Although swiftly advancing insights underscore the regulatory role of purinergic signalling on mood-related behaviour and stress reactivity, along with their pathological modifications using novel brain-penetrant P2X7R antagonists (JNJ-54175446, JNJ-55308942) undergoing phase 2 clinical trials for depression treatment [27,129], there remains an insufficient comprehension of the role of variation in P2RX7 in the background of depressive-like behaviours.