Modulation of [3H]quinpirole binding to dopaminergic receptors by adenosine A2A receptors

Activation of Adensine A1 and A2A Receptors Modulates Dopamine D2 Receptor‐Induced Responses in Stably Transfected Human Neuroblastoma Cells

“…Our results demonstrate that adenosine A 2A and A 1 receptors can exert an antagonistic acute and tonic modulatory role on dopamine D 2 receptor-mediated functions, respectively. Activation of adenosine A 2A receptors, as previously described in other models, antagonistically modulates the binding and functional characteristics of dopamine D 2 receptors (Ferré et al, 1991b(Ferré et al, , 1992(Ferré et al, , 1993b(Ferré et al, , 1994Pollack and Fink, 1995;Yang et al, 1995;Dasgupta et al, 1996;Latini et al, 1996;Mayfield et al, 1996;Lepiku et al, 1997;Fuxe et al, 1998;Rimondini et al, 1998). Activation of adenosine A 1 receptors could down-regulate D 2 receptor signal transduction and/or the effectors modulated by activation of D 2 receptors, i.e., voltage-gated ionic channels controlling cell excitability.…”

Photoactivatable Dopamine and Sulpiride to Explore the Function of Dopaminergic Neurons and Circuits

“…For initial tests, CyHQ-sulpiride was photolyzed with a long flash (1 s) from and LED (6.5 mW) (Figure ). The time constant of decay for quinpirole (τ = 635 ms) was significantly slower than that of dopamine (τ = 307 ms), which dissociates faster ( k off = 1.69 min –1 ) than quinpirole ( k off = 0.17 min –1 ) ( p = 0.0011 by t test, n = 4 and 2 for quinpirole and dopamine, respectively). The amplitude of the peak response of the agonists were not significantly different, so cannot be considered a confounding factor.…”

Molecular Mechanisms and Therapeutical Implications of Intramembrane Receptor/Receptor Interactions among Heptahelical Receptors with Examples from the Striatopallidal GABA Neurons

“…At the biochemical level, by using membrane preparations of rat striatum or of cell lines expressing the corresponding receptors and by using receptor autoradiography in rat and human striatal sections, it has been shown that stimulation of A 2A receptors decreases the affinity of D 2 receptors for dopamine or dopamine agonists. These results were shown, e.g., as an increase in K H or IC 50 in competition experiments of dopamine versus a radioactively labeled D 2 receptor antagonist or as an increase in K D in saturation experiments with tritiated dopamine or quinpirole (Ferré et al, 1991d(Ferré et al, , 1994a(Ferré et al, ,b, 1999aDasgupta et al, 1996a;Dixon et al, 1997;Lepiku et al, 1997;Kull et al, 1999;Franco et al, 2000;Salim et al, 2000;Díaz-Cabiale et al, 2001). In receptor autoradiography experiments, the A 2A receptor-mediated modulation of D 2 receptor binding properties was found to be stronger in the ventral compared with the dorsal striatum (Ferré et al, 1994b;Díaz-Cabiale et al, 2001).…”

“…In this way, the excitation and increased energy expenditure brought about by the ATP P 2Y1 receptor activation begins to be counteracted even at a moment when the extracellular ATP has not been broken down to adenosine, the major ligand for the A 1 receptor (Fredholm, 1995a,b;Ferré and Fuxe, 2000;Fredholm et al, 2001 (Ferré et al, 1991d). This offered a novel mechanism for the reported antagonistic adenosine/dopamine interactions found in the brain (Ferré, , 1997Fuxe et al, 1993Fuxe et al, , 1998Lepiku et al, 1997). The molecular mechanism was proposed to be one of heteromerization of A 2A /D 2 receptors (Zoli et al, 1993).…”