Adenosine--an endogenous neuroprotective metabolite and neuromodulator.

Adenosine is now widely accepted as the major inhibitory neuromodulator in the central nervous system besides GABA. It has been suggested to be an endogenous neuroprotective metabolite. In situations of metabolic stress, e.g. ischemia adenosine decreases energy demand and increases energy supply. Of particular relevance in this context is its modulation of glutamate release. A shift of this adenosine-glutamate balance in favor of adenosine helps to restore function at the cellular, organ and organism level. Adenosine A1 receptor agonists and metabolic inhibitors, e.g. of transport, deaminase and xanthine oxidase have been demonstrated to be effective in different animal models of ischemia. Nimodipine, a L-type channel calcium antagonist currently in clinical trials for stroke and dementia syndromes, has now been shown to be a potent adenosine transport inhibitor in clinically relevant concentrations. Increase of adenosinergic neuromodulation may well be one of several future therapeutic strategies in neuroprotection.