Profiles of the Affinity of Antipsychotic Drugs for Neurotransmitter Receptors
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Kitakanto Med.J. 87 48( 2 ) : 87•`102, 1998 PROFILES OF THE AFFINITY OF ANTIPSYCHOTIC DRUGS FOR NEUROTRANSMITTER RECEPTORS AND THEIR CLINICAL IMPLICATION Kimie Yonemura, Kazuo Miyanaga, and Yukiteru Machiyama Departmentof Neuropsychiatry,Gunma UniversitySchool of Medicine Abstract : The binding affinities of 12 different neurotransmitter receptors were measured using a radio-labeled receptor assay. The profiles of the pharmacological affinities of 20 antipsychotic drugs were assessed. Based on the Ki values for the D2 receptor, 5HT2 receptor, and ƒ¿1 receptor, the antipsychotic drugs were classified into five groups (i.e., three anti-DA activity predominant groups and two anti-5HT activity predominant groups). A theoretical basis for drug choice in clinical settings is also proposed. We recommend that the groups of the drugs having predominantly anti-DA activity be used in the treatment of hallucinations and delusions and that the drugs in the anti-5HT activity predominant group be used to treat hypobulia. If it is necessary to administer two or more of these drugs together, we propose that they should be drugs with different profiles. Extrapyramidal symptoms, side effects of antipsychotic drugs, were interpreted in terms of interaction among the anti-D, activity, anti-5HT2 activity, and anti-Ach activity. Key words : Antipsychotic drugs, Anti-DA action, Anti-5HT action, Anti-adrenergic action, Extrapyramidal symptoms. (Kitakanto Med.J. 48 (2) : 87•`102, 1998) number of reports on the affinity of antipsychotic INTRODUCTION agents for receptors have been published both in Japan A variety of antipsychotic agents have been devel- and other countrieso. The reports, however, have often oped for clinical use since 1952, when the effectiveness dealt with drugs that are seldom used or not used at all of chlorpromazine in treating schizophrenia was first at present in Japan. demonstrated. However, selection of antipsychotic The present study was undertaken to assess the drugs in individual cases has often been empirical, affinity for receptors of clinically popular antipsy- without any definite theoretical or pharmacological chotic drugs, and to obtain comprehensive profiles of guidelines. This is corroborated by the tendency for their pharmacologic actions, with the ultimate goal of psychiatrists in different countries to prescribe different providing a theoretical basis for selecting drugs in drugs for the same mental symptom and there are also individual clinical cases. differences between university hospitals and other MATERIALS AND METHODS hospitals within Japan. As a result of recent advances in pharmacological Nineteen antipsychotic drugs on the market in research on neurotransmitter receptors in the brain, the Japan and one that is currently being developed were mechanism of action of antipsychotic drugs has been investigated by radiolabeled receptor assay1•`7) in increasingly elucidated, and it now seems possible to regard to their affinity for the receptors of 12 different argue for the establishment of theoretical foundations neurotransmitters. for the selection of drugs to treat mental symptoms. A Materials and methods ( [3H] ligands, membrane Received : December 22, 1997 Accepted : January 21, 1998 Address : KIMIE YONEMURA Department of Neuropsychiatry Gunma University School of Medicine 3-39-22 Showamachi, Maebashi, Gunma, 371-8511, Japan 88 Yonemura, Miyanaga, Machiyama Table 1. Materials and methods preparation, buffers, incubation conditions and the 50mM Tris/HCl (120mM NaCl, 5mM MgC12, 5mM drugs to test for nonspecific binding) are summarized KCl, 1.5mM CaC12, 5mM EDTA : pH7.4) and in 25 in Table 1. volumes of 50mM Tris/HCl (120mM NaCl, 5mM KCl, 5mM MgC12, 1mM EDTA : pH7.4), respectively. I . Membrane preparation C. Serotonin lA (5HT1A) receptor A. Dopamine 1 (D1) receptor and dopamine 2 (D2) Hippocampus of the male Wistar rat (200-250g) receptor was used. The method of homogenation was the same Striatum of male Wistar rat (200-250g) was procedure described in the paragraph of dopamine 1 homogenized in 30 volumes of 50mM Tris/HC1 (pH receptor and dopamine 2 receptor. 7.5) with an ultrasonic homogenizer (Nihonseiki Fac- D. Serotonin 3 (5HT3) receptor tory). The homogenate was centrifuged at 50,000 •~ g Cerebral cortex of male Wistar rat (200-250g) was for 20 min and the pellet was resuspended in 30 vol- used. The method of homogenation was the same umes of 50mM Tris/HC1 (pH7.5), and the same proce- procedure described in the paragraph of dopamine 1 dure was repeated two more times. The resulting pellet receptor and dopamine 2 receptor, except for the kind was then suspended in 3 volumes of the same buffer. In of buffer (50mM HEPES : pH7.5). the binding assay, the suspension was diluted to an E. Serotonin 2 (5HT2) receptor, adrenaline ƒ¿1 (ƒ¿1) appropriate concentration and used as the crude mem- receptor, adrenaline ƒ¿2 (ƒ¿2) receptor, and branes fraction for the binding assay. acetylcholine (Ach) receptor B. Dopamine 3 (D3) receptor and Dopamine 4 (D4) Cerebral cortex of male Wistar rat (200-250g) was receptor used. The method of homogenation was the same The membranes from Chinese hamster ovary procedure described in the paragraph of dopamine 1 (CHO) cells expressing the cloned human dopamine receptor and dopamine 2 receptor. D3 receptor and D4 receptor were used. These materi- F. Histamine 1 (H1) receptor als were obtained from the Yamanouchi Pharmaceuti- Brain stem of male Wistar rat (200-250g) was used. cal Co.,Ltd. and DuPont, respectively. They were The method of homogenation was the same procedure stored frozen at -70•Ž until used. Before the binding described in the paragraph of dopamine 1 receptor and study, the membranes were diluted in 7.5 volumes of dopamine 2 receptor. 89 The affinity of antipsychotic drugs for receptors G. Sigma (ƒÐ) receptor spiperone solution (DuPont-NEN), 100ƒÊl of displac- Whole brain of male Wistar rat (200-250g) was ing drugs (antipsychotic drugs), 700ƒÊl of 50mM Tris/ used. The method of homogenation was the same HC1 (120mM NaCl, 5mM KCl, 1mM MgC12, 1mM procedure described in the paragraph of dopamine 1 CaC12 ; pH7.5), and 100ƒÊl of resuspended homogenate receptor and dopamine 2 receptor. (0.1-0.2mg protein/tube). Incubation conditions were 37°C for 30min. Nonspecific binding was determined All suspensions were stored frozen at -70•Ž. Before in the presence of 10ƒÊM sulpiride (SIGMA). the 5HT1, receptor and ƒÐ receptor binding assays, the (3) D3 receptor suspension was incubated for 20 min at 37•Ž and 60 The receptor binding assay was performed accord- min at 37•Ž, respectively. The protein concentration ing to the method of Tada et al11). was measured by the method of Lowry, with bovine The binding assay consisted of 100ƒÊl of 4nM [3H] serum albumin as the protein standard. YM-09151-2 (nemonapride) solution (DuPont-NEN), 100ƒÊl of displacing drugs (antipsychotic drugs), II. Antipsychotic drugs 1700ƒÊl of 50mM Tris/HCl (120mM NaC1, 5mM The antipsychotic drugs used in this study and their MgC12, 5mM KCl, 1.5mM CaC12, 5mM EDTA ; sources were as follows : Chlorpromazine HCl, pH7.4), and 100ƒÊl of membrane suspension (8/2g levomepromazine maleate, propericiazine, perphen- prot./tube). Incubation conditions were 25°C for 30 azine maleate, fluphenazine maleate, clotiapine, min. Nonspecific binding was determined in the haloperidol, bromperidol, carpipramine HCl, cloca- presence of 10ƒÊM Quinpirol (RBI). pramine HCl HCland mosapramine, from Yoshitomi Phar- (4) D4 receptor maceutical Ind., Ltd. ; thioridazine HCl and oxyper- The receptor binding assay was performed accord- tine, from Sandoz Pharmaceuticals Ltd. ; zotepine, ing to the method of Van Tol et al.12). pimozide, and sulpiride, from Fujisawa Pharmaceuti- The binding assay consisted of 100ƒÊl of 50nM [3H] cal Co.,Ltd. ; timiperone, from Daiichi Pharmaceuti- spiperone solution (DuPont-NEN), 100ƒÊl of displac- cal Co.,Ltd. ; sultopride HCl, from Dainippon Phar- ing drugs (antipsychotic drugs), 700ƒÊl of 50mM Tris/ maceutical Co.,Ltd. ; nemonapride, from Yamanouchi HCl (120mM NaCl, 5mM KCl, 5mM MgC12, 1mM Pharmaceutical Co.,Ltd. ; and SM-9018, from EDTA ; pH7.4), and 100ƒÊl of membrane suspension Sumitomo Pharmaceutical Co.,Ltd.. (22ƒÊl prot./tube). Incubation conditions were 25°C Most of the drugs used as displacing drugs were for 60 min. Nonspecific binding was determined in the dissolved in distilled water, but, propericiazine, presence of 100ƒÊM nemonapride (Yamanouchi Phar- clotiapine, zotepine, haloperidol, timiperone, maceutical Co.,Ltd.). bromperidol, and pimozide were dissolved in 0.1% 13, 5HT receptor lactic acid. (1) 5HT1, receptor The receptor binding assay was performed accord- III. Radio Receptor Assays ing to the method of Peroutka et al.'3). A. DA receptor The binding assay consisted of 100ƒÊl of 6nM [3H] (1) D1 receptor 8-OH-DPAT solution (DuPont-NEN), 100ƒÊl of dis- The receptor binding assay was performed accord- placing drugs (antipsychotic drugs), 100ƒÊl of 0.1% ing to the method of Billard et al.8). ascorbic acid, 100ƒÊl of 10nM pargyline (SIGMA), The binding assay consisted of 100ƒÊl of 2nM [3H] 500ƒÊl of 50mM Tris/Hl (pH7.5), and 100ƒÊl of SCH23390 solution (DuPont-NEN), 100ƒÊl of displac- resuspended homogenate (0.10-0.15mg prot./tube). ing drugs (antipsychotic drugs), 700ƒÊl of 50mM Tris/ Incubation conditions were 30•Ž for 20min. Non- HC1 (120mM NaCl, 5mM KCl, 1mM MgC12, 1mM specific binding was determined in the presence of CaC12 ; pH7.5), and 100ƒÊl of resuspended homogenate 10ƒÊM serotonin (SIGMA). (0.1mg protein/tube). Incubation conditions were (2) 5HT2 receptor 37°C for 30 min. Nonspecific binding was determined The receptor binding assay was performed accord- in the presence of 10ƒÊM fluphenazine (Yoshitomi ing to the method of Leysen et al14). Pharmaceutical Ind. Ltd.). The binding assay consisted of 100ƒÊl of 10nM [3H] (2) D2 receptor ketanserin solution (DuPont-NEN), 100ƒÊl of displac- The receptor binding assay was performed accord- ing drugs (antipsychotic drugs), 700ƒÊl of 50mM Tris/ ing to the method of Creese et al.9). and Seeman et HCl (pH7.5), and 100ƒÊl of resuspended homogenate al.10).