The purines ATP and adenosine are widely recognized for their neuromodulatory effects. They have been
shown to have effects on neurons via various receptors and interactions with glial cells. In particular, long-term
potentiation (LTP) in hippocampal slice preparations has been found to be modulated by ATP and adenosine. This review
gives an overview of purinergic signaling in relation to hippocampal LTP and memory formation. The data supports the
hypothesis that adenosine mediates a tonic suppression of synaptic transmission. Thus, low adenosine levels appear to
increase basal synaptic activity via a decreased activation of the inhibitor A1 receptor, consequently making it more
difficult to induce LTP because of lower contrast. During high stimulation, the inhibition of neighboring pathways by
adenosine, in combination with an A2a receptor activation, appears to increase contrast of excited pathways against a nonexcited
background. This would enable amplification of specific signaling while suppressing non-specific events.
Although a clear role for purinergic signaling in LTP is evident, more studies are needed to scrutinize the modulatory role
of ATP and adenosine and their receptors in synaptic plasticity and memory.
Keywords: ATP, adenosine, LTP, hippocampus, memory, synaptic plasticity.
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