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Adenosine A 1 receptor‐mediated inhibition of dopamine release from rat striatal slices is modulated by D 1 dopamine receptors
Author(s) -
O'Neill C.,
Nolan B. J.,
Macari A.,
O'Boyle K. M.,
O'Connor J. J.
Publication year - 2007
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2007.05953.x
Subject(s) - sch 23390 , agonist , chemistry , dopamine , adenosine , cgs 21680 , dopamine receptor d1 , medicine , endocrinology , adenosine receptor , dopamine receptor , adenosine a1 receptor , dopamine receptor d2 , receptor , pharmacology , biology , biochemistry
Dopamine release is regulated by presynaptic dopamine receptors and interactions between adenosine and dopamine receptors have been well documented. In the present study, dopamine release from isolated striatal slices from Wistar rats was measured using fast cyclic voltammetry. Single‐pulse stimulation (0.1 ms, 10 V) was applied every 5 min over a 2‐h period. Superfusion with the adenosine (A) 1 receptor agonist N 6 ‐cyclopentyladenosine (CPA), but not the A 2 receptor agonist 3‐[4‐[2‐[[6‐amino‐9‐[(2R,3R,4S,5S)‐5‐(ethylcarbamoyl)‐3,4‐dihydroxy‐oxolan‐2‐yl]purin‐2‐yl]amino]ethyl] phenyl]propanoic acid (CGS 21680), inhibited dopamine release in a concentration‐dependent manner (IC 50 3.80 × 10 −7 m ; n = 10). The dose–response curve to CPA was shifted to the right (IC 50 6.57 × 10 −6 m ; n = 6, P < 0.05 vs. control) by the A 1 receptor antagonist 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX). Neither the D 1 agonist 6‐chloro‐APB nor the D 1 antagonist R‐(+)‐8‐chloro‐2,3,4,5‐tetrahydro‐3‐methyl‐5‐phenyl‐1H‐3‐ benzazepine‐7‐ol (SCH 23390) altered dopamine release on their own. However, SCH 23390 (3 µ m ) significantly attenuated the response to CPA (IC 50 1.44 × 10 −5 m ; n = 6, P < 0.01 vs. control). Furthermore, the inhibitory effect of CPA was significantly increased in the presence of 6‐chloro‐APB (1 µ m ). In radioligand binding experiments, CPA interacted with high‐ and low‐affinity states of [ 3 H]DPCPX‐lableled A 1 receptors. The high‐affinity agonist binding to A 1 receptors was inhibited by the stable guanosine triphosphate analogue Gpp(NH)p. In contrast, neither the proportion nor the affinity of high‐affinity A 1 receptors was altered by dopamine or SCH 23390. These results provide evidence that the inihibition of dopamine release by adenosine A 1 receptors is dependent, at least in part, on the simultaneous activation of D 1 dopamine receptors. While the mechanism underlying this interaction remains to be determined, it does not appear to involve an intramembrane interaction between A 1 and D 1 receptors.