Time of day determines modulation of synaptic transmission by adenosine inthe rat hippocampal slices

Adenosine, an endogenous modulator of synaptic transmission, has been impli cated in regulation of sleep and arousal. The effect of adenosine on neuron al excitability depends on its concentration in the extracellular space. Th e present study shows that the state of activity of laboratory rats determi nes the level of ton ic inhibition by adenosine in hippocampal slices prepa red from these animals. Thus, slices taken at the end of the active period showed significantly more inhibition by adenosine, as determined by the eff ects of the Al receptor blocker 8-CPT, in comparison to slices taken in the inactive state. The results support the proposed role of adenosine in regu lation of sleep and arousal and point to the importance of the time of day at which slices for electrophysiological experiments are prepared. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.