ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: 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). Similarly, the typical neuroleptics increased A2a receptor densities, whereas the atypical neuroleptics did not (control, 536.9 ± 8.7 fmol/mg of protein; haloperidol, 687.9 ± 28.0 fmol/mg of protein; fluphenazine, 701.1 ± 31.6 fmol/mg of protein; sulpiride, 563.3 ± 27.2 fmol/mg of protein; clozapine, 550.9 ± 40.9 fmol/mg of protein). There were no differences in affinities for [3H]CGS-21680 or [3H]sulpiride among the various treatment groups. This study demonstrates that typical neuroleptics induce comparable up-regulation in both striatal D2 and A2a receptors. Thus, A2a receptors might be a pharmacologic target for the development of novel therapeutic strategies to minimize the adverse effects of antipsychotic treatment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1471-4159.1995.65052057.x
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