[Purinergic regulatory complex in the brain synapses].

The fast and precise neuron-to-neuron signalling at the synapses is one of the most crucial processes in the central nervous system (CNS) function. Recent advances in the functional and morphological analysis of the brain synapses have identified adenosine 5'-triphosphate (ATP), a ubiquitous and most important molecule in the intracellular functions, to play important roles also as an extracellular messenger at synapses. Lines of evidence accumulated until today indicate that ATP (1) is released into the extracellular space particularly from astrocytes through specific mechanisms, (2) activates specific receptors for extracellular ATP, which modifies synaptic transmission, and (3) is hydrolysed to adenosine by ecto-nucleotidases, which in turn activates specific adenosine receptors modulating synaptic transmission. We have recently shown, using the patch-clamp recording of postsynaptic membrane currents in the acute brain slice preparations in vitro, that (1) ATP activates ATP-gated Ca2+ -permeable channels (P2X receptor channels) on presynaptic terminal membrane, triggering glutamate release without action potential, and (2) adenosine, produced from ATP in the extracellular milieu, activates presynaptic G protein-coupled receptors, which reduces Ca2+ entry through voltage-dependent Ca2+ channels and suppresses action potential-dependent transmitter release. These distinct mechanisms operate in synergy in various CNS structures and form the "purinergic regulatory complex" of the synaptic transmission.