Neuroleptics up-regulate adenosine A2a receptors in rat striatum: implications for the mechanism and the treatment of tardive dyskinesia.
Neuroleptics, which are potent dopamine receptor antagonists, are used to treat psychosis. In the striatum, dopamine subtype-2 (D2) receptors interact with high-affinity adenosine subtype-2 (A2a) receptors. To examine the effect of various neuroleptics on the major subtypes of striatal dopamine and adenosine receptors, rats received 28 daily intraperitoneal injections of these drugs. Haloperidol (1.5 mg/kg/day) increased the density of striatal D2 receptors by 24% without changing their affinity for [3H]sulpiride. Haloperidol increased the density of striatal A2a receptors by 33% (control, 522.4 +/- 20.7 fmol/mg of protein; haloperidol, 694.6 +/- 23.6 fmol/mg of protein; p < 0.001) without changing their affinity for [3H]CGS-21680 (control, 19.2 +/- 2.2 nM; haloperidol, 21.4 +/- 2.3 nM). In contrast, haloperidol had no such effect on striatal dopamine subtype-1 (D1) and adenosine subtype-1 (A1) receptors. Binding characteristics and the pharmacological displacement profile of the increased [3H]CGS-21680 binding sites confirmed them as A2a receptors. Comparing different classes of neuroleptics showed that the typical neuroleptics haloperidol and fluphenazine (1.5 mg/kg/day) increased D2 receptor densities, whereas the atypical neuroleptics sulpiride (100 mg/kg/day) and clozapine (20 mg/kg/day) did not (control, 290.3 +/- 8.7 fmol/mg of protein; haloperidol, 358.1 +/- 6.9 fmol/mg of protein; fluphenazine, 381.3 +/- 13.6 fmol/mg of protein; sulpiride, 319.8 +/- 18.9 fmol/mg of protein; clozapine, 309.2 +/- 13.7 fmol/mg of protein).(ABSTRACT TRUNCATED AT 250 WORDS)
Parsons
B
B
Department of Psychiatry, Columbia University, College of Physicians and Surgeons, New York, New York, USA.
Togasaki
D M
DM
Kassir
S
S
Przedborski
S
S
D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D003342:Corpus Striatum / Q000378:metabolism*; D004409:Dyskinesia, Drug-Induced / Q000503:physiopathology / Q000628:therapy; D005476:Fluphenazine / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D018047:Receptors, Purinergic P1 / Q000378:metabolism*; D013469:Sulpiride / Q000378:metabolism; D015854:Up-Regulation
D014150:Antipsychotic Agents; D018047:Receptors, Purinergic P1; D013469:Sulpiride; D006220:Haloperidol; D005476:Fluphenazine