PURINOCEPTORS IN THE CENTRAL-NERVOUS-SYSTEM

New exciting developments on the occurrence and functional role of pur inoceptors in mammalian brain were presented at the session ''Purinoce ptors in the central nervous system'' chaired by Flaminio Cattabeni an d Tom Dunwiddie at the Purines '96 international conference. The focus of the session were topics of recent interest, including the sources and mechanisms involved in ATP and adenosine release during physiologi cal neurotransmission in hippocampus, the brain expression of the rece ntly cloned P2 receptors, and the role of the various adenosine recept or subtypes in brain protection from neurodegeneration associated with trauma-, ischemia- and excessive excitatory amino acid neurotransmiss ion. New important insights into the mechanisms responsible for the fo rmation and release of adenosine into the extracellular space were pro vided by data obtained by Dunwiddie and coworkers in hippocampal pyram idal neurons. These data may have functional implications for the role of purines in modulation of synaptic plasticity and long-term potenti ation in this brain area, and hence in cognitive functions. Buell prov ided an updated overview on the cloning, molecular characteristics and brain expression of various ligand-gated P2X purinoceptors; although the functional role of these receptors in mammalian brain still awaits elucidation, their widespread distribution in the nervous system stro ngly suggests that ATP-mediated events are more prevalent and importan t in brain than expected. Pedata presented data on the functional inte rrelationships between adenosine and glutamate in the brain, and also provided evidence for alterations of the reciprocal regulation between these two systems in aged brain, which may have important implication s for both ischemia- and trauma-associated neurodegenerative events an d senescence-associated cognitive impairment. Finally, von Lubitz prov ided novel data on the molecular mechanisms likely to be at the basis of the brain protective effects associated with the chronic stimulatio n of the adenosine A(3) receptor, further confirming that this recepto r represents a crucial target for the development of new antiischemic and antineurodegenerative therapeutic agents. (C) 1997 Wiley-Liss, Inc .