1
|
Stip E, Lungu OV, Anselmo K, Letourneau G, Mendrek A, Stip B, Lipp O, Lalonde P, Bentaleb LA. Neural changes associated with appetite information processing in schizophrenic patients after 16 weeks of olanzapine treatment. Transl Psychiatry 2012; 2:e128. [PMID: 22714121 PMCID: PMC3384221 DOI: 10.1038/tp.2012.53] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
There is evidence that some atypical antipsychotics, including olanzapine, can produce unwanted metabolic side effects, weight gain and diabetes. However, neuronal correlates of change related to food information processing have not been investigated with these medications. We studied the effect of a pharmacological manipulation with an antipsychotic known to cause weight gain on metabolites, cognitive tasks and neural correlates related to food regulation. We used functional magnetic resonance imaging in conjunction with a task requiring visual processing of appetitive stimuli in schizophrenic patients and healthy controls before and after 16 weeks of antipsychotic medication with olanzapine. In patients, the psychological and neuronal changes associated following the treatment correlated with appetite control measures and metabolite levels in fasting blood samples. After 16 weeks of olanzapine treatment, the patients gained weight, increased their waist circumference, had fewer positive schizophrenia symptoms, a reduced ghrelin plasma concentration and an increased concentration of triglycerides, insulin and leptin. In premotor area, somatosensory cortices as well as bilaterally in the fusiform gyri, the olanzapine treatment increased the neural activity related to appetitive information in schizophrenic patients to similar levels relative to healthy individuals. However, a higher increase in sensitivity to appetitive stimuli after the treatment was observed in insular cortices, amygdala and cerebellum in schizophrenic patients as compared with healthy controls. Furthermore, these changes in neuronal activity correlated with changes in some metabolites and cognitive measurements related to appetite regulation.
Collapse
Affiliation(s)
- E Stip
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada.
| | - O V Lungu
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada,Centre de Recherche de l′Institut Universitaire de gériatrie de Montréal, Université de Montréal, Montréal, QC, Canada,Department of Research, Donald Berman Maimonides Geriatric Center, Montréal, QC, Canada
| | - K Anselmo
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada,CHUM, Centre de Recherche Fernand Seguin, Université de Montréal, Notre Dame Hospital, Montréal, QC, Canada
| | - G Letourneau
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada,CHUM, Centre de Recherche Fernand Seguin, Université de Montréal, Notre Dame Hospital, Montréal, QC, Canada
| | - A Mendrek
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada,CHUM, Centre de Recherche Fernand Seguin, Université de Montréal, Notre Dame Hospital, Montréal, QC, Canada
| | - B Stip
- École Polytechnique de Montréal, Montréal, QC, Canada
| | - O Lipp
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada,Centre de Recherche de l′Institut Universitaire de gériatrie de Montréal, Université de Montréal, Montréal, QC, Canada
| | - P Lalonde
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada,CHUM, Centre de Recherche Fernand Seguin, Université de Montréal, Notre Dame Hospital, Montréal, QC, Canada
| | - L A Bentaleb
- Department of Psychiatry, Université de Montréal, Montréal, QC, Canada,CHUM, Centre de Recherche Fernand Seguin, Université de Montréal, Notre Dame Hospital, Montréal, QC, Canada
| |
Collapse
|
2
|
Psychopharmacological treatment of schizophrenia: What do we have, and what could we get? Neuropharmacology 2012; 62:1371-80. [DOI: 10.1016/j.neuropharm.2011.03.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 03/07/2011] [Accepted: 03/10/2011] [Indexed: 12/20/2022]
|
3
|
|
4
|
Harrison-Read PE. Antimanic potency of typical neuroleptic drugs and affinity for dopamine D2 and serotonin 5-HT2A receptors--a new analysis of data from the archives and implications for improved antimanic treatments. J Psychopharmacol 2009; 23:899-907. [PMID: 18635692 DOI: 10.1177/0269881108094349] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Datasets of antimanic potency ratings and receptor-binding affinities [inhibition constants (K(i))] at dopamine D2 and serotonin 5-HT2A brain receptors were accessed from published literature for a large series (n = 24) of typical neuroleptic drugs, many of which are now obsolete and unobtainable. There was a strong positive association between antimanic potency and affinity for D2 receptors, in support of a 'dopamine-blockade hypothesis' of antimanic drug action. Taking the series of neuroleptics as a whole, there was no association between antimanic potency and affinity for 5-HT2A receptors. Despite this, within a subsample of typical neuroleptics with low affinity for D2 receptors resembling new generation atypical antipsychotics, a positive association between antimanic potency and affinity for 5-HT2A receptors emerged. This suggests that blockade of brain 5-HT2A receptors plays at least a subsidiary role in the antimanic effects of some typical neuroleptics. Other considerations also suggest that combining drugs to achieve high affinity for and blockade of both dopamine D2 receptors and serotonin 5-HT2A receptors, possibly with additional direct or indirect stimulation of postsynaptic 5-HT1A receptors, might maximize antimanic efficacy.
Collapse
Affiliation(s)
- P E Harrison-Read
- Department of Psychiatry, Royal Free Hospital, Pond Street, London, UK.
| |
Collapse
|
5
|
A 5-HT2A receptor inverse agonist, ACP-103, reduces tremor in a rat model and levodopa-induced dyskinesias in a monkey model. Pharmacol Biochem Behav 2008; 90:540-4. [PMID: 18534670 DOI: 10.1016/j.pbb.2008.04.010] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Revised: 04/07/2008] [Accepted: 04/11/2008] [Indexed: 11/24/2022]
Abstract
A potent 5-hydroxytryptamine (5-HT)2A receptor inverse agonist and antagonist, ACP-103 [N-(4-fluorophenylmethyl)-N-(1-methylpiperidin-4-yl)-N'-(4-(2-methylpropyloxy)phenylmethyl) carbamide (2R,3R)-dihydroxybutanedioate (2:1, active:salt)], was evaluated for its ability to reduce the primary motor symptom of tremor using tacrine-induced tremulous jaw movements in rats, which is an animal model of parkinsonian tremor. Furthermore, ACP-103 was evaluated for its ability to reduce levodopa-induced dyskinesias in monkeys rendered parkinsonian with MPTP [1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine]. ACP-103 reduced tacrine-induced tremulous jaw movements in rats. In addition, ACP-103 administered in combination with levodopa caused a dose-related reduction in dyskinesias in monkeys. These data suggest that ACP-103 may have the potential to reduce tremor and levodopa-induced dyskinesias in Parkinson's disease.
Collapse
|
6
|
Marazziti D, Lucacchini A, Baroni S, Betti L, Catena M, Giannaccini G, Dell'Osso B, Masala I, Mungai F, Dell'Osso L. Presence of D4 dopamine receptors in human prefrontal cortex: a postmortem study. BRAZILIAN JOURNAL OF PSYCHIATRY 2008; 29:148-52. [PMID: 17639254 DOI: 10.1590/s1516-44462007000200011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 01/16/2007] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The aim of our study was to explore the presence and the distribution of D4 dopamine receptors in postmortem human prefrontal cortex, by means of the binding of [3H]YM-09151-2, an antagonist that has equal affinity for D2, D3 and D4 receptors. It was therefore necessary to devise a unique assay method in order to distinguish and detect the D4 component. METHOD Frontal cortex samples were harvested postmortem, during autopsy sessions, from 5 subjects. In the first assay, tissue homogenates were incubated with increasing concentrations of [3H]YM-09151-2, whereas L-745870, which has a high affinity for D4 and a low affinity for D2/D3 receptors, was used as the displacer. In the second assay, raclopride, which has a high affinity for D2/D3 receptors and a low affinity for D4 receptors, was used to block D2/D3. The L-745870 (500 nM) was added to both assays in order to determine the nonspecific binding. RESULTS Our experiments revealed the presence of specific and saturable binding of [3H]YM-09151-2. The blockade of D2 and D3 receptors with raclopride ensured that the D4 receptors were labeled. The mean maximum binding capacity was 88 +/- 25 fmol/mg protein, and the dissociation constant was 0.8 +/- 0.4 nM. DISCUSSION AND CONCLUSIONS Our findings, although not conclusive, suggest that the density of D4 receptors is low in the human prefrontal cortex.
Collapse
Affiliation(s)
- Donatella Marazziti
- Department of Psychiatry, Neurobiology, Pharmacology and Biotechnology, University of Pisa, Pisa, Italy.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Abstract
Thirty years ago, psychiatrists had only a few choices of old neuroleptics available to them, currently defined as conventional or typical antipsychotics, as a result schizophrenics had to suffer the severe extra pyramidal side effects. Nowadays, new treatments are more ambitious, aiming not only to improve psychotic symptoms, but also quality of life and social reinsertion. Our objective is to briefly but critically review the advances in the treatment of schizophrenia with antipsychotics in the past 30 years. We conclude that conventional antipsychotics still have a place when just the cost of treatment, a key factor in poor regions, is considered. The atypical antipsychotic drugs are a class of agents that have become the most widely used to treat a variety of psychoses because of their superiority with regard to extra pyramidal symptoms. We can envisage different therapeutic strategies in the future, each uniquely targeting a different dimension of schizophrenia, be it positive, negative, cognitive or affective symptoms.
Collapse
Affiliation(s)
- I R De Oliveira
- Department of Neuropsychiatry, School of Medicine, Federal University of Bahia, Salvador, BA, Brazil.
| | | |
Collapse
|
8
|
Basta-Kaim A, Budziszewska B, Jaworska-Feil L, Tetich M, Leśkiewicz M, Kubera M, Lasoń W. Chlorpromazine inhibits the glucocorticoid receptor-mediated gene transcription in a calcium-dependent manner. Neuropharmacology 2002; 43:1035-43. [PMID: 12423673 DOI: 10.1016/s0028-3908(02)00149-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Antipsychotic drugs can modulate transcription factors and also nuclear receptors, but their action on glucocorticoid receptors (GR)-members of the steroid/thyroid hormone receptor family has not been studied so far. In the present study we investigated effects of various antipsychotics on the glucocorticoid-mediated gene transcription in fibroblast cells, stably transfected with a mouse mammary tumor virus promoter (LMCAT cells). Chlorpromazine (3-100 microM) inhibited the corticosterone-induced gene transcription in a concentration- and time-dependent manner. Clozapine showed a similar, but less potent effect, while haloperidol acted only in high concentrations, and other antipsychotic drugs (sulpiride, raclopride, remoxipride) were without any effect. It was also found that a phorbol ester (an activator of protein kinase C (PKC)) and A-23187 (Ca(2+)-ionophore) attenuated the inhibitory effect of chlorpromazine on the GR-induced gene transcription. An antagonist of the L-type Ca(2+) channel, as well as an inhibitor of phospholipase C (PLC) inhibited the corticosterone-induced gene transcription, but had no effect on the chlorpromazine-induced changes. The involvement of a PKC/PLC pathway in the chlorpromazine action was confirmed by Western blot analysis which showed that the drug in question decreased the PLC-beta(1) protein level, and to a lesser extent that of the PKC-alpha protein in LMCAT cells. The aforementioned data suggest that inhibition of the glucocorticosteroid-induced gene transcription by chlorpromazine and clozapine may be a mechanism by which these drugs block some effects induced by glucocorticoids. The inhibitory effect of chlorpromazine on the corticosterone-induced gene transcription seems to depend on the inhibition of Ca(2+) influx and/or the inhibition of some calcium-dependent enzymes, e.g. phospholipase beta(1).
Collapse
Affiliation(s)
- A Basta-Kaim
- Department of Endocrinology, Institute of Pharmacology, Polish Academy of Sciences, 12 Smetna Street, 31-343 Kraków, Poland
| | | | | | | | | | | | | |
Collapse
|
9
|
Tauscher J, Jones C, Remington G, Zipursky RB, Kapur S. Significant dissociation of brain and plasma kinetics with antipsychotics. Mol Psychiatry 2002; 7:317-21. [PMID: 11920159 DOI: 10.1038/sj.mp.4001009] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2001] [Accepted: 10/09/2001] [Indexed: 11/08/2022]
Abstract
Current dosing regimens of psychotropic drugs are based on plasma kinetic considerations, although it is unclear whether plasma levels faithfully reflect brain kinetics of drugs.(1,2) To examine this, we compared the kinetics of plasma levels of two widely used antipsychotics, olanzapine and risperidone, vs the time course of their effects in the brain. We used positron emission tomography (PET) and [(11)C]-labeled ligands to quantify striatal and extra-striatal dopamine-2 (D(2)), and cortical serotonin-2A (5-HT(2A)) receptor occupancy in healthy subjects after a single dose, and in patients chronically treated for psychosis. We found a significant dissociation of brain and plasma kinetics. Mean plasma elimination half-lives of single doses of olanzapine and risperidone were 24.2 and 10.3 h, respectively, whereas it took on average 75.2 h with olanzapine, and 66.6 h with risperidone to decline to 50% of their peak striatal D(2) receptor occupancy. We found similar discrepancies between the time course of plasma levels and extra-striatal D(2) as well as 5-HT(2A) receptor occupancy. Our results question the current reliance on plasma kinetics as the main basis for dosing regimens of antipsychotics. Studies of brain kinetics may provide a sounder basis for determining dosing schedules of psychotropic medications.
Collapse
Affiliation(s)
- Johannes Tauscher
- Schizophrenia-PET Program, Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.
| | | | | | | | | |
Collapse
|
10
|
Sidhu A, Niznik HB. Coupling of dopamine receptor subtypes to multiple and diverse G proteins. Int J Dev Neurosci 2000; 18:669-77. [PMID: 10978845 DOI: 10.1016/s0736-5748(00)00033-2] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The family of five dopamine receptors subtypes activate cellular effector systems through G proteins. Historically, dopamine receptors were thought to only stimulate or inhibit adenylyl cyclase, by coupling to either G(s)alpha or G(i)alpha, respectively. Recent studies in transfected cells, reviewed here, have shown that multiple and highly diverse signaling pathways are activated by specific dopamine receptor subtypes. This multiplicity of signaling responses occurs through selective coupling to distinct G proteins and each of the receptors can interact with more than one G protein. Although some of the multiple coupling of dopamine receptors to different G proteins occurs from within the same family of G proteins, these receptors can also couple to G proteins belonging to different families. Such multiple interactions between receptors and G proteins elicits functionally distinct physiological effects which acts to enhance and subsequently suppress the original receptor response, and to activate apparently distinct signaling pathways. In the brain, where coexpression of functionally distinct receptors in heterogeneous cells further adds to the complexity of dopamine signaling, minor alterations in receptor/G protein coupling states during either development or in adults, may underlie the imbalanced signaling seen in dopaminergic-linked diseases such as schizophrenia, Parkinson's disease and attention deficit hyperactivity disorder.
Collapse
Affiliation(s)
- A Sidhu
- Laboratory of Molecular Neurochemistry, Department of Pediatrics, Georgetown University Medical Center, Georgetown University, 3970 Reservoir Road, NW, Washington, DC 20007, USA.
| | | |
Collapse
|
11
|
Kruzich PJ, See RE. An evaluation of the role of 5-HT(2) receptor antagonism during subchronic antipsychotic drug administration in rats. Brain Res 2000; 875:35-43. [PMID: 10967296 DOI: 10.1016/s0006-8993(00)02574-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A widely postulated mechanism of action for the atypical profile of many novel antipsychotic drugs (APDs) is their relatively high affinity for 5-HT(2) receptors. The present study investigated motor function and striatal dopamine (DA) efflux and metabolism in rats given 21 daily injections of drugs that differed in 5-HT(2) affinity. These drugs included: risperidone (high 5-HT(2A/2C)/high D(2)), clozapine (high 5-HT(2A/2C)/low D(2)), haloperidol (low 5-HT(2A/2C)/high D(2)), haloperidol+ritanserin (selective 5-HT(2A/2C)), or vehicle. Rats injected with haloperidol (0.5 mg/kg) or haloperidol+ritanserin (0.5 mg/kg and 1.0 mg/kg, respectively) showed extreme catalepsy on day 1, but significantly decreased catalepsy when tested again on days 7 and 21. Acute or subchronic risperidone (0.05 or 0.5 mg/kg), clozapine (20 mg/kg), or vehicle did not induce significant catalepsy. Microdialysis performed 24 h after the last injection demonstrated that rats treated with risperidone, clozapine, or vehicle showed similar increases in DA efflux and metabolism following an acute injection of a selective DA D(2/3) antagonist (raclopride, 0.5 mg/kg). DA efflux showed an attenuated response to raclopride in the haloperidol alone group; this effect was less apparent in the haloperidol+ritanserin group. However, both of these groups showed a similar tolerance effect to the raclopride-induced increase in DA metabolites. These results suggest that the profile seen after subchronic risperidone more closely resembles clozapine than haloperidol. While ritanserin reduced the tolerance-like effects of haloperidol on striatal DA efflux, the overall results demonstrate that potent 5-HT(2) blockade alone may not entirely account for the distinctive profile of novel APDs.
Collapse
Affiliation(s)
- P J Kruzich
- Department of Physiology and Neuroscience, Medical University of South Carolina, 167 Ashley Avenue, Charleston, SC 29425, USA
| | | |
Collapse
|
12
|
Abstract
The recent enthusiasm among clinicians for the so-called 'atypical antipsychotics' has both improved treatment for schizophrenic patients and provided a welcome stimulus for basic research on antipsychotic mechanisms. Even the newer drugs have shortcomings, and research is underway aimed at identifying novel agents with greater efficacy and safety. Much of this effort is directed towards compounds which, in addition to blocking dopamine receptors, also act on other neurotransmitter receptors such as 5-HT2, 5-HT1A and alpha2-adrenergic receptors. However, there is also a large amount of scientific activity seeking to discover and develop selective dopamine receptor subtype antagonists (including compounds which specifically block D3 or D4 receptors) or drugs that specifically target the dopamine autoreceptor. Finally, a number of drug development programmes are searching for non-dopaminergic antipsychotics. Drugs that do not have affinity for dopamine receptors but act through neurotensin, sigma or cannabinoid CB1 receptors or glutamatergic mechanisms are currently being evaluated. If any of these agents prove to have clinical efficacy this may lead to a third generation of antipsychotics. It is likely, however, that the mechanisms of action of such drugs will nevertheless imply the intimate involvement of dopaminergic pathways.
Collapse
Affiliation(s)
- B Scatton
- Discovery Research, Sanofi-Synthelabo Research, Bagneux, France.
| | | |
Collapse
|
13
|
Nasu R, Matsuo H, Takanaga H, Ohtani H, Sawada Y. Quantitative prediction of catalepsy induced by amoxapine, cinnarizine and cyclophosphamide in mice. Biopharm Drug Dispos 2000; 21:129-38. [PMID: 11180191 DOI: 10.1002/1099-081x(200005)21:4<129::aid-bdd224>3.0.co;2-f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Parkinsonism can be a side effect of antipsychotic drugs, and has recently been reported with peripherally acting drugs such as calcium channel blockers, antiarrhythmic agents and so on. In this study, we examined the quantitative prediction of drug-induced catalepsy by amoxapine, cinnarizine and cyclophosphamide, which have been reported to induce parkinsonism. Dose-dependent catalepsy was induced by these drugs in mice. In vivo dopamine D(1), D(2) and muscarinic acetylcholine (mACh) receptor occupancies by these drugs in the striatum were also examined. The in vitro binding affinities (K(i) values) of amoxapine and cinnarizine to dopamine D(1), D(2) and mACh receptors in rat striatal synaptic membrane were 200 and 2900 nM, 58.4 and 76.4 nM and 379 and 290 nM, respectively. Cyclophosphamide did not bind to these receptors at concentrations up to 100 microM. Twenty drugs, including those mentioned above, showed a significant correlation between the observed intensity of catalepsy and the values predicted with a pharmacodynamic model (Haraguchi K, Ito K, Kotaki H, Sawada Y, Iga T. Prediction of drug-induced catalepsy based on dopamine D(1), D(2), and muscarinic acetylcholine receptor occupancies. Drug Metab Disp 1997; 25: 675-684) based on in vivo occupancy of dopamine D(1), D(2) and mACh receptors. We conclude that occupancy of dopamine D(1) and D(2) receptors contributes to catalepsy induction by amoxapine and cinnarizine.
Collapse
Affiliation(s)
- R Nasu
- Department of Medico-Pharmaceutical Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan
| | | | | | | | | |
Collapse
|
14
|
Kalkman HO, Neumann V, Hoyer D, Tricklebank MD. The role of alpha2-adrenoceptor antagonism in the anti-cataleptic properties of the atypical neuroleptic agent, clozapine, in the rat. Br J Pharmacol 1998; 124:1550-6. [PMID: 9723970 PMCID: PMC1565533 DOI: 10.1038/sj.bjp.0701975] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The mechanism underlying the anticataleptic properties of the atypical neuroleptic agent, clozapine, has been investigated in the rat. 2.The close structural analogues of clozapine, loxapine (0.1 mg kg(-1) s.c.) and iso-clozapine (1 and 3 mg kg(-1) s.c.) induced catalepsy in rats. In contrast, clozapine and the regio-isomer of loxapine, iso-loxapine (up to 10 mg kg(-1) s.c.) did not produce catalepsy, but at a dose of 1 mg kg(-1) significantly inhibited catalepsy induced by loxapine (0.3 mg kg(-1) s.c.). 3. Radioligand binding assays showed that cataleptogenic potential was most clearly predicted by the D2/5-HT1A, D2/5-HT1B/1D and D2/alpha2-receptor affinity (KD) ratios: i.e. 30-100-fold higher ratios were calculated for loxapine and iso-clozapine, whereas the ratios were less than 1 for clozapine and iso-loxapine. The ratios of affinities for D2 to 5-HT2A, 5-HT2C or D1 did not reflect the grouping of cataleptic and non-cataleptic compounds. 4. Co-treatment with the alpha2-adrenoceptor antagonists, yohimbine (1-10 mg kg(-1) s.c.), RX 821002 (1-10 mg kg(-1) s.c.) and MK-912 (0.3 and 1 mg kg(-1) s.c.) dose-dependently inhibited the cataleptic response to loxapine (0.3 mg kg(-1)). Yohimbine (1-10 mg kg(-1) s.c.) also dose-dependently inhibited the cateleptic response to haloperidol (0.3 mg kg(-1) s.c.). The alpha2-adrenoceptor antagonists had no effect per se. 5. Neither yohimbine (10 mg kg(-1)) nor RX821002 (3 mg kg(-1)) altered the cataleptic response to the D1 receptor antagonist, SCH 23390 (1 mg kg(-1) s.c.), while, like clozapine, both compounds abolished the response to the 5-HT2A receptor antagonist, MDL 100,151 (3 mg kg(-1) s.c.). 6. The present data strongly implicate alpha2-adrenoceptor blockade in the anticataleptic properties of clozapine and suggest that its lack of extrapyramidal side effects in the clinic may also be a consequence of this property.
Collapse
Affiliation(s)
- H O Kalkman
- Nervous Systems Research, Novartis Pharma AG, Basel, Switzerland
| | | | | | | |
Collapse
|
15
|
Wilson JM, Sanyal S, Van Tol HH. Dopamine D2 and D4 receptor ligands: relation to antipsychotic action. Eur J Pharmacol 1998; 351:273-86. [PMID: 9721018 DOI: 10.1016/s0014-2999(98)00312-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Since the discovery that the antipsychotic action of phenothiazines was mediated by dopamine D2 receptors, the dopamine system has been scrutinized for schizophrenia related abnormalities. The focus has been to create neuroleptics with improved antipsychotic profiles and reduced side effects. With the identification of multiple dopamine receptor subtypes, the hypotheses regarding the role of dopamine in schizophrenia and antipsychotic action of neuroleptics have been refined. Even after the molecular identification of newer dopamine D2-like receptor subtypes (D3 and D4), the dopamine D2 receptor is still considered the predominant site for antipsychotic action. However, there has been much debate concerning the modulatory role of other dopamine receptor sites in the mechanism of action of antipsychotic drugs. Specifically, the dopamine D4 receptor has received much attention in this regard, since the atypical antipsychotic agent, clozapine, preferentially blocks this receptor subtype as compared with dopamine D2 and D3 receptors. In this review we will highlight some of the observations and arguments regarding the involvement of the dopamine D2 and D4 receptor sites in the therapeutic efficacy of antipsychotic medication.
Collapse
Affiliation(s)
- J M Wilson
- Laboratory for Molecular Neurobiology,3 Clarke Institute of Psychiatry, Toronto, Ontario, Canada
| | | | | |
Collapse
|