Activation of adenosine A1 and A2A receptors modulates dopamine D2 receptor-induced responses in stably transfected human neuroblastoma cells.
Adenosine can influence dopaminergic neurotransmission in the basal ganglia via postsynaptic interaction between adenosine A2A and dopamine D2 receptors. We have used a human neuroblastoma cell line (SH-SY5Y) that was found to express constitutively moderate levels of adenosine A1 and A2A receptors (approximately 100 fmol/mg of protein) to investigate the interactions of A2A/D2 receptors, at a cellular level. After transfection with human D2L receptor cDNA, SH-SY5Y cells expressed between 500 and 1,100 fmol of D2 receptors/mg of protein. In membrane preparations, stimulation of adenosine A2A receptors decreased the affinity of dopamine D2 receptors for dopamine. In intact cells, the calcium concentration elevation induced by KCI treatment was moderate, and dopamine had no effect on either resting intracellular free Ca2+ concentration ([Ca2+]i) or KCI-induced responses. In contrast, pretreatment with adenosine deaminase for 2 days dramatically increased the elevation of [Ca2+]i evoked by KCI, which then was totally reversed by dopamine. The effects induced by 48-h adenosine inactivation were mimicked by application of adenosine A1 antagonists and could not be further reversed by acute activation of either A1 or A2A receptors. Acute application of the selective A2 receptor agonist CGS-21680 counteracted the D2 receptor-induced [Ca2+]i responses. The present study shows that SH-SY5Y cells are endowed with functional adenosine A2A and A1 receptors and that A2A receptors exert an antagonistic acute effect on dopamine D2 receptor-mediated functions. In contrast, A1 receptors induce a tonic modulatory role on these dopamine functions.
Salim
H
H
CNRS, Institut Alfred Fessard, Gif-sur-Yvette, France.
Ferré
S
S
Dalal
A
A
Peterfreund
R A
RA
Fuxe
K
K
Vincent
J D
JD
Lledo
P M
PM
D000241:Adenosine / Q000037:antagonists & inhibitors / Q000172:deficiency; D000243:Adenosine Deaminase / Q000494:pharmacology; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000378:metabolism; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism / Q000502:physiology*; D018047:Receptors, Purinergic P1 / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043705:Receptor, Adenosine A2A; D017448:Receptors, Dopamine D2; D018047:Receptors, Purinergic P1; D000243:Adenosine Deaminase; D000241:Adenosine; D002118:Calcium; D004298:Dopamine