Adenosine receptors--the role in modulation of dopamine and glutamate release in the rat striatum.

The aim of present study was to assess the role of activation of adenosine A-1 and A-2a receptors in the modulation of dopamine (DA) and glutamate release in the rat striatum by microdialysis in freely moving animals. Adenosine A-1 receptor agonist N6-cyclopentyladenosine (CPA) and A-2a receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680) were administered locally into the striatum through microdialysis probe. CPA (10, 100 and 500 microM) did not affect basal levels of DA or glutamate. In contrast, CGS 21680 at the concentrations of 10, 50 and 100 microM increased in a dose-dependent manner the level of DA and at 100 microM also the level of glutamate. Both agonists at the concentration of 100 microM inhibited KCl-induced (100 mM) DA and glutamate release. The present results suggest, that in physiological conditions only excitatory effects of adenosine may be observed and adenosine A-2a receptors seem to be involved. During depolarization with KCl, adenosine, by inhibiting excessive outflow of neurotransmitters mediated via A-1 and A-2a receptors, manifests its protective role as homeostatic neuromodulator.