Inhibition of noradrenaline release from hippocampal slices by a stable adenosine analogue.

Electrical field stimulation elicits a calcium-dependent release of 3H-NA from rat hippocampal slices. The release is inhibited by the alpha 2-agonist clonidine and enhanced by the alpha 2-antagonist yohimbine. The stable adenosine analogue N6-L-phenylisopropyl-adenosine (L-PIA) caused a dose-dependent inhibition of 3H-NA overflow. The effect of L-PIA was antagonized by the adenosine receptor antagonist 8-phenyl-theophylline, which caused a slight, but significant increase in overflow per se. The results suggest that there are functionally important presynaptic adenosine receptors on nor-adrenergic nerve terminals in the rat hippocampus.