RT Journal Article
SR Electronic
T1 The Role of Extracellular Adenosine in Regulating Mossy Fiber Synaptic Plasticity
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2832
OP 2837
DO 10.1523/JNEUROSCI.4260-04.2005
VO 25
IS 11
A1 Maria Kukley
A1 Maximilian Schwan
A1 Bertil B. Fredholm
A1 Dirk Dietrich
YR 2005
UL http://www.jneurosci.org/content/25/11/2832.abstract
AB Hippocampal mossy fiber synapses show unique molecular features and dynamic range of plasticity. A recent paper proposed that the defining features of mossy fiber synaptic plasticity are caused by a local buildup of extracellular adenosine (Moore et al., 2003). In this study, we reassessed the role of ambient adenosine in regulating mossy fiber synaptic plasticity in mouse and rat hippocampal slices. Synaptic transmission was highly sensitive to activation of presynaptic adenosine A1 receptors (A1Rs), which reduced transmitter release by >75%. However, most of A1Rs were not activated by ambient adenosine. Field potentials increased only by 20-30% when A1Rs were fully blocked with the A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) (1 μm). Moreover, blocking A1Rs hardly altered paired-pulse facilitation, frequency facilitation, or posttetanic potentiation. Frequency facilitation was similar in A1R-/- mice and when measured with NMDA receptor-mediated EPSCs in CA3 pyramidal cells in the presence of DPCPX. Additional experiments suggested that the results obtained by Moore et al. (2003) can partially be explained by their usage of a submerged recording chamber and elevated divalent cation concentrations. In conclusion, a reduction of the basal release probability by ambient adenosine does not underlie presynaptic forms of plasticity at mossy fiber synapses.