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Noback M, Bhakta SG, Talledo JA, Kotz JE, Benster L, Roberts BZ, Nungaray JA, Light GA, Swerdlow NR, Brigman JL, Cavanagh JF, Young JW. Amphetamine increases motivation of humans and mice as measured by breakpoint, but does not affect an Electroencephalographic biomarker. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2024; 24:269-278. [PMID: 38168850 PMCID: PMC11060428 DOI: 10.3758/s13415-023-01150-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/15/2023] [Indexed: 01/05/2024]
Abstract
Translation of drug targets from preclinical studies to clinical trials has been aided by cross-species behavioral tasks, but evidence for brain-based engagement during task performance is still required. Cross-species progressive ratio breakpoint tasks (PRBTs) measure motivation-related behavior and are pharmacologically and clinically sensitive. We recently advanced elevated parietal alpha power as a cross-species electroencephalographic (EEG) biomarker of PRBT engagement. Given that amphetamine increases breakpoint in mice, we tested its effects on breakpoint and parietal alpha power in both humans and mice. Twenty-three healthy participants performed the PRBT with EEG after amphetamine or placebo in a double-blind design. C57BL/6J mice were trained on PRBT with EEG (n = 24) and were treated with amphetamine or vehicle. A second cohort of mice was trained on PRBT without EEG (n = 40) and was treated with amphetamine or vehicle. In humans, amphetamine increased breakpoint. In mice, during concomitant EEG, 1 mg/kg of amphetamine significantly decreased breakpoint. In cohort 2, however, 0.3 mg/kg of amphetamine increased breakpoint consistent with human findings. Increased alpha power was observed in both species as they reached breakpoint, replicating previous findings. Amphetamine did not affect alpha power in either species. Amphetamine increased effort in humans and mice. Consistent with previous reports, elevated parietal alpha power was observed in humans and mice as they performed the PRBT. Amphetamine did not affect this EEG biomarker of effort. Hence, these findings support the pharmacological predictive validity of the PRBT to measure effort in humans and mice and suggest that this EEG biomarker is not directly reflective of amphetamine-induced changes in effort.
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Affiliation(s)
- Michael Noback
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - Savita G Bhakta
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - Jo A Talledo
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - Juliana E Kotz
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - Lindsay Benster
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - Benjamin Z Roberts
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - John A Nungaray
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - Gregory A Light
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
- Research Service MIRECC, VISN 22, Veterans Affairs San Diego Healthcare System, San Diego, CA, USA
| | - Neal R Swerdlow
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA
| | - Jonathan L Brigman
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - James F Cavanagh
- Psychology Department, University of New Mexico, Albuquerque, NM, USA
| | - Jared W Young
- Department of Psychiatry, University of California, San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA, 92093-0804, USA.
- Research Service MIRECC, VISN 22, Veterans Affairs San Diego Healthcare System, San Diego, CA, USA.
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Clozapine reliably increases the motivation for food: parsing the role of the 5-HT 2c and H 1 receptors. Psychopharmacology (Berl) 2020; 237:957-966. [PMID: 31897573 DOI: 10.1007/s00213-019-05425-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 12/06/2019] [Indexed: 10/25/2022]
Abstract
RATIONALE AND OBJECTIVES Although clozapine is effective in treating schizophrenia, it is associated with adverse side effects including weight gain and metabolic syndrome. Despite this, the role of clozapine on feeding behaviour and food intake has not been thoroughly characterised. Clozapine has a broad pharmacological profile, with affinities for several neurotransmitter receptors, including serotonin (5-hydroxytriptamine, 5-HT) and histamine. Given that the serotonin 5-HT2C receptor and histaminergic H1 receptor are involved in aspects of feeding behaviour, the effect of clozapine on feeding may be linked to its action at these receptors. METHODS We assessed, in rats, the effect of acute and subchronic administration of clozapine on responding for food under a progressive ratio (PR) schedule under conditions of food restriction and satiety. We also examined the effect of antagonists of the serotonin 5-HT2C and histaminergic H1 receptors on the same schedule. Clozapine reliably increased responding for food, even when rats had ad libitum access to food. The effect of clozapine on responding for food was reproduced by combined (but not individual) antagonism of the serotonin 5-HT2C and histaminergic H1 receptors. CONCLUSION These findings show that clozapine enhances the motivation to work for food, that this effect is stable over repeated testing, and is independent of hunger state of the animal. This effect may relate to a combined action of clozapine at the serotonin 5-HT2C and histaminergic H1 receptors.
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Abela AR, Li Z, Lê AD, Fletcher PJ. Clozapine reduces nicotine self-administration, blunts reinstatement of nicotine-seeking but increases responding for food. Addict Biol 2019; 24:565-576. [PMID: 29575323 DOI: 10.1111/adb.12619] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 01/19/2018] [Accepted: 02/11/2018] [Indexed: 11/30/2022]
Abstract
People with schizophrenia display significantly higher rates of smoking than the general population, which may be due to an interaction between nicotine and antipsychotic medication. While the conventional antipsychotic drug haloperidol sometimes increases cigarette smoking in patients with schizophrenia, there is some evidence suggesting that clozapine, an atypical antipsychotic drug, may reduce nicotine use in these patients. However, the effects of antipsychotic drugs like clozapine on aspects of nicotine self-administration and reinstatement have not been systematically examined. In the current study, we assessed the effect of clozapine on nicotine self-administration under fixed ratio and progressive ratio schedules of reinforcement, as well as reinstatement of nicotine-seeking following a period of abstinence. To determine the specificity of its effect on nicotine reward, we also tested the effect of clozapine on responding for food reinforcement under fixed ratio and progressive ratio schedules. For comparison, we also examined the effects of haloperidol, a first-generation antipsychotic drug, under some of the same behavioral conditions as clozapine. We show that clozapine inhibits nicotine self-administration and reinstatement of nicotine-seeking but also increases the amount of effort that rats will exert for food reward. In contrast, haloperidol at a wide range of doses attenuated responding for nicotine and food reward, suggestive of a non-specific reduction in reinforcer efficacy. These results show the potential utility of clozapine as a smoking cessation treatment for patients with schizophrenia, in addition to its antipsychotic properties.
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Affiliation(s)
- Andrew R. Abela
- Centre for Addiction and Mental HealthPreclinical Research and Campbell Family Mental Health Research Institute Toronto ON Canada
- Department of PsychiatryUniversity of Toronto Toronto ON Canada
| | - Zhaoxia Li
- Centre for Addiction and Mental HealthPreclinical Research and Campbell Family Mental Health Research Institute Toronto ON Canada
| | - Anh D. Lê
- Centre for Addiction and Mental HealthPreclinical Research and Campbell Family Mental Health Research Institute Toronto ON Canada
- Department Pharmacology and ToxicologyUniversity of Toronto Toronto ON Canada
| | - Paul J. Fletcher
- Centre for Addiction and Mental HealthPreclinical Research and Campbell Family Mental Health Research Institute Toronto ON Canada
- Department Pharmacology and ToxicologyUniversity of Toronto Toronto ON Canada
- Department of PsychiatryUniversity of Toronto Toronto ON Canada
- Department of PsychologyUniversity of Toronto Toronto ON Canada
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Abstract
The second-generation antipsychotic drug olanzapine has become a widely prescribed drug in the treatment of schizophrenia and bipolar disorder. Unfortunately, its therapeutic benefits are partly outweighed by significant weight gain and other metabolic side effects, which increase the risk for diabetes and cardiovascular disease. Because olanzapine remains superior to other antipsychotic drugs that show less weight gain liability, insight into the mechanisms responsible for olanzapine-induced weight gain is crucial if it is to be effectively addressed. Over the past few decades, several groups have investigated the effects of olanzapine on energy balance using rat models. Unfortunately, results from different studies have not always been consistent and it remains to be determined which paradigms should be used in order to model olanzapine-induced weight gain most accurately. This review summarizes the effects of olanzapine on energy balance observed in different rat models and discusses some of the factors that appear to contribute to the inconsistencies in observed effects. In addition it compares the effects reported in rats with clinical findings to determine the predictive validity of different paradigms.
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den Boon FS, Body S, Hampson CL, Bradshaw CM, Szabadi E, de Bruin N. Effects of amisulpride and aripiprazole on progressive-ratio schedule performance: comparison with clozapine and haloperidol. J Psychopharmacol 2012; 26:1231-43. [PMID: 21969105 DOI: 10.1177/0269881111421974] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Clozapine and some other atypical antipsychotics (e.g. quetiapine, olanzapine) have been found to exert a characteristic profile of action on operant behaviour maintained by progressive-ratio schedules, as revealed by Killeen's Mathematical Principles of Reinforcement model of schedule-controlled behaviour. These drugs increase the value of a parameter that expresses the 'incentive value' of the reinforcer (a) and a parameter that is inversely related to the organism's 'motor capacity' (δ). This experiment examined the effects of two further atypical antipsychotics, aripiprazole and amisulpride, on progressive-ratio schedule performance in rats; the effects of clozapine and a conventional antipsychotic, haloperidol, were also examined. In agreement with previous findings, clozapine (4, 8 mg kg⁻¹) increased a and δ, whereas haloperidol (0.05, 0.1 mg kg⁻¹) reduced a and increased δ. Aripiprazole (3,30 mg kg⁻¹) increased δ but did not affect a. Amisulpride (5, 50 mg kg⁻¹) had a delayed and protracted effect: δ was increased 3-6 hours after treatment; a was increased 1.5 hours, and reduced 12-24 hours after treatment. Interpretation based on Killeen's model suggests that aripiprazole does not share clozapine's ability to enhance reinforcer value. Amisulpride produced a short-lived enhancement, followed by a long-lasting reduction, of reinforcer value. Both drugs impaired motor performance.
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Affiliation(s)
- F S den Boon
- Psychopharmacology Section, Division of Psychiatry, University of Nottingham, Nottingham, UK
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Olarte-Sánchez CM, Valencia Torres L, Body S, Cassaday HJ, Bradshaw CM, Szabadi E, Goudie AJ. A clozapine-like effect of cyproheptadine on progressive ratio schedule performance. J Psychopharmacol 2012; 26:857-70. [PMID: 21890589 DOI: 10.1177/0269881111408961] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The atypical antipsychotic drug clozapine has multiple pharmacological actions, some of which, including 5-hydroxytryptamine (5-HT₂) and histamine (H₁) receptor antagonist effects, are shared by the non-selective 5-HT receptor antagonist cyproheptadine. Atypical antipsychotics have a characteristic profile of action on operant behaviour maintained by progressive ratio schedules, as revealed by Killeen's (1994) mathematical model of schedule controlled behaviour. These drugs increase the values of a parameter that expresses the 'incentive value' of the reinforcer (a) and a parameter that is inversely related to the 'motor capacity' of the organism (δ). This experiment examined the effects of acute treatment with cyproheptadine and clozapine on performance on a progressive ratio schedule of food reinforcement in rats; the effects of a conventional antipsychotic, haloperidol, and two drugs with food intake-enhancing effects, chlordiazepoxide and Δ⁹-tetrahydrocannabinol (THC), were also examined. Cyproheptadine (1, 5 mg kg⁻¹) and clozapine (3.75, 7.5 mg kg⁻¹) increased a and δ. Haloperidol (0.05, 0.1 mg kg⁻¹) reduced a and increased δ. Chlordiazepoxide (3, 10 mg kg⁻¹) increased a but reduced δ. THC (1, 3 mg kg⁻¹) had no effect. Interpretation based on Killeen's (1994) model suggests that cyproheptadine and clozapine enhanced the incentive value of the reinforcer and impaired motor performance. Motor impairment may be due to sedation (possibly reflecting H₁ receptor blockade). Enhancement of incentive value may reflect simultaneous blockade of H₁ and 5-HT₂ receptors, which has been proposed as the mechanism underlying the food intake-enhancing effect of cyproheptadine. In agreement with previous findings, haloperidol impaired motor performance and reduced the incentive value of the reinforcer. Chlordiazepoxide's effect on a is consistent with its food intake-enhancing effect.
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Affiliation(s)
- C M Olarte-Sánchez
- Psychopharmacology Section, Division of Psychiatry, University of Nottingham, Nottingham, UK
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Clozapine increases reward evaluation but not overall ingestive behaviour in rats licking for sucrose. Psychopharmacology (Berl) 2011; 216:411-20. [PMID: 21360098 DOI: 10.1007/s00213-011-2237-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 02/13/2011] [Indexed: 10/18/2022]
Abstract
RATIONALE Clozapine and the "atypical" antipsychotics are less prone than neuroleptics to induce extrapyramidal motor effects, worsening of the negative symptoms of schizophrenia and dysphoria. This is paralleled by preclinical evidence showing reduced suppression of behaviours aimed at the pursuit of reward, with increased measures of reward efficacy. Serotonin 5-HT2 receptors seem to play a role in determining this profile. OBJECTIVE We investigated the effects of clozapine on the microstructure of ingestive behaviour, which might reveal behavioural dimensions, such as reward evaluation and behavioural activation, which might be relevant in explaining its atypical profile. Moreover, we investigated the possibility that coadministration of the typical antipsychotic haloperidol and the 5-HT2A/2C receptor antagonist ritanserin might mimic clozapine effects. MATERIALS AND METHODS The effects of clozapine (0.5, 1 and 5 mg/kg) and of the coadministration of haloperidol (0.05 mg/kg) and ritanserin (0.5 and 3 mg/kg) have been examined on the microstructure of licking for a 10% sucrose solution in rats. RESULTS Clozapine failed to affect whole ingestion as revealed by the lack of effect on lick number. However, it increased reward evaluation at the dose of 1 mg/kg, as revealed by increased mean bout size. Haloperidol resulted in a decreased bout size. Ritanserin failed to exert any effects either alone or when coadministered with haloperidol. CONCLUSION The ability of clozapine to increase reward evaluation might contribute to explain its atypical profile both in the clinical setting and in preclinical studies. These results suggest that 5-HT2A/2C receptors are not involved in the observed effect.
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Orsi A, Rees D, Andreini I, Venturella S, Cinelli S, Oberto G. Overview of the marmoset as a model in nonclinical development of pharmaceutical products. Regul Toxicol Pharmacol 2011; 59:19-27. [PMID: 21156195 PMCID: PMC7126225 DOI: 10.1016/j.yrtph.2010.12.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 11/17/2010] [Accepted: 12/07/2010] [Indexed: 01/14/2023]
Abstract
Callithrix jacchus (common marmoset) is one of the more primitive non-human primate species and is used widely in fundamental biology, pharmacology and toxicology studies. Marmosets breed well in captivity with good reproductive efficiencies and their sexual maturity is reached within 18 months of age allowing for rapid expansion of colonies and early availability of sexually mature animals permitting an earlier assessment of product candidates in the adult. Their relatively small size allows a reduction in material requirements leading to a reduction in development time and cost. Fewer animals are also required due to their ability to be used in both pharmacology and toxicology (nonclinical) studies. These factors, alongside a better understanding of their optimal nutrient and welfare requirements over recent years, facilitate the generation of a more cohesive and robust dataset. With the growth of biotechnology-derived pharmaceuticals, non-human primate use has, by necessity, also increased; nevertheless, there is also a growing public call for minimizing their use. Utilizing, the more primitive marmoset species may provide the optimal compromise and once the scientific rationale has been carefully considered and their use justified, there are several advantages to using the marmoset as a model in nonclinical development of pharmaceutical products.
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Affiliation(s)
- Antonia Orsi
- Salupont Consulting Ltd., Kent Science Park, 940 Cornforth Drive, Sittingbourne, Kent, ME9 8PX, UK.
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O'Tuathaigh CMP, Kirby BP, Moran PM, Waddington JL. Mutant mouse models: genotype-phenotype relationships to negative symptoms in schizophrenia. Schizophr Bull 2010; 36:271-88. [PMID: 19934211 PMCID: PMC2833123 DOI: 10.1093/schbul/sbp125] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Negative symptoms encompass diminution in emotional expression and motivation, some of which relate to human attributes that may not be accessible readily in animals. Additionally, their refractoriness to treatment precludes therapeutic validation of putative models. This review considers critically the application of mutant mouse models to the study of the pathobiology of negative symptoms. It focuses on 4 main approaches: genes related to the pathobiology of schizophrenia, genes associated with risk for schizophrenia, neurodevelopmental-synaptic genes, and variant approaches from other areas of neurobiology. Despite rapid advances over the past several years, it is clear that we continue to face substantive challenges in applying mutant models to better understand the pathobiology of negative symptoms: the majority of evidence relates to impairments in social behavior, with only limited data relating to anhedonia and negligible data concerning avolition and other features; even for the most widely examined feature, social behavior, studies have used diverse assessments thereof; modelling must proceed in cognizance of increasing evidence that genes and pathobiologies implicated in schizophrenia overlap with other psychotic disorders, particularly bipolar disorder. Despite the caveats and challenges, several mutant lines evidence a phenotype for at least one index of social behavior. Though this may suggest superficially some shared relationship to negative symptoms, it is not yet possible to specify either the scope or the pathobiology of that relationship for any given gene. The breadth and depth of ongoing studies in mutants hold the prospect of addressing these shortcomings.
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Affiliation(s)
- Colm M. P. O'Tuathaigh
- Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, St Stephen's Green, Dublin 2, Ireland,To whom correspondence should be addressed; tel: +353-1-402-2377, fax: +353-1-402-2453, e-mail:
| | - Brian P. Kirby
- School of Pharmacy, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Paula M. Moran
- School of Psychology, University of Nottingham, Nottingham, UK
| | - John L. Waddington
- Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, St Stephen's Green, Dublin 2, Ireland
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Buhusi CV, Meck WH. Effect of clozapine on interval timing and working memory for time in the peak-interval procedure with gaps. Behav Processes 2006; 74:159-67. [PMID: 17141425 PMCID: PMC1849977 DOI: 10.1016/j.beproc.2006.10.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Revised: 10/09/2006] [Accepted: 10/09/2006] [Indexed: 01/26/2023]
Abstract
Previous research indicates that dopamine controls both the speed of an internal clock [Maricq, A.V., Church, R.M., 1983. The differential effects of haloperidol and methamphetamine on time estimation in the rat. Psychopharmacology 79, 10-15] and sharing of resources between the timer and other cognitive processes [Buhusi, C.V., 2003. Dopaminergic mechanisms of interval timing and attention. In: Meck, W.H. (Ed.), Functional and Neural Mechanisms of Interval Timing. CRC Press, Boca Raton, FL, pp. 317-338]. For example, dopamine agonist methamphetamine increases the speed of an internal clock and resets timing after a gap, while dopamine antagonist haloperidol decreases the speed of an internal clock and stops timing during a gap [Buhusi, C.V., Meck, W.H., 2002. Differential effects of methamphetamine and haloperidol on the control of an internal clock. Behav. Neurosci. 116, 291-297]. Using a 20-s peak-interval procedure with gaps we examined the acute effects of clozapine (2.0mg/kg i.p.), which exerts differential effects on dopamine and serotonin in the cortex and striatum, two brain areas involved in interval timing and working memory. Relative to saline, clozapine injections shifted the response functions leftward both in trials with and without gaps, suggesting that clozapine increased the speed of an internal clock and facilitated the maintenance of the pre-gap interval in working memory. These results suggest that clozapine exerts effects in different brain areas in a manner that allows for the pharmacological separation of clock speed and working memory as a function of peak trials without and with gaps.
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Affiliation(s)
- Catalin V Buhusi
- Duke University, Department of Psychology and Neuroscience, Durham, NC 27708, United States.
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MacDonald CJ, Meck WH. Differential effects of clozapine and haloperidol on interval timing in the supraseconds range. Psychopharmacology (Berl) 2005; 182:232-44. [PMID: 16001114 DOI: 10.1007/s00213-005-0074-8] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2005] [Accepted: 03/13/2005] [Indexed: 11/30/2022]
Abstract
The effects of clozapine (0.6, 1.2, and 2.4 mg/kg) and haloperidol (0.03, 0.06, and 0.12 mg/kg) on the timing of 10, 30, and 90-s intervals were characterized in rats. Each drug's effect on timing behavior was assessed following intraperitoneal injections using a variant of the peak-interval procedure. Although haloperidol proportionately shifted peak times rightward in a manner consistent with a decrease in clock speed, clozapine exerted the opposite effect and proportionately shifted peak times leftward in a manner consistent with an increase in clock speed. These results support the proposal that typical antipsychotic drugs such as haloperidol and atypical antipsychotic drugs such as clozapine exert differential effects on dopaminergic, serotonergic, and glutamatergic systems within the cortex and striatum, two brain regions shown to be crucial for interval timing.
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Affiliation(s)
- Christopher J MacDonald
- Department of Psychological and Brain Sciences, Duke University, Genome Sciences Research Building II, 3rd Floor, P.O. Box 91050, Durham, NC 27708, USA
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Zhang Z, Rickard JF, Asgari K, Body S, Bradshaw CM, Szabadi E. Quantitative analysis of the effects of some "atypical" and "conventional" antipsychotics on progressive ratio schedule performance. Psychopharmacology (Berl) 2005; 179:489-97. [PMID: 15565430 DOI: 10.1007/s00213-004-2049-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Accepted: 09/21/2004] [Indexed: 10/26/2022]
Abstract
RATIONALE Performance on progressive ratio schedules has been proposed as a means of assessing the effects of drugs on the value or "efficacy" of reinforcers. A mathematical model affords a basis for quantifying the effects of drugs on progressive ratio schedule performance. According to this model, the relation between response rate and ratio size is described by a bitonic (inverted-U) function. One parameter of the function, alpha, expresses the motivational or "activating" effect of the reinforcer (duration of activation of responding produced by the reinforcer), whereas another parameter, delta, expresses the minimum time needed to execute a response, and is regarded as an index of "motor capacity". In a previous experiment we found that the "atypical" antipsychotic clozapine increased alpha, indicating an increase in the efficacy of a food reinforcer. OBJECTIVE We examined the effects of four "atypical" and four "conventional" antipsychotics on progressive ratio schedule performance. METHODS Rats responded for a sucrose reinforcer (0.6 M, 50 microl) on a time-constrained progressive ratio schedule (50-min sessions). After 90 preliminary training sessions, they received acute doses of antipsychotics (doses in mg kg(-1)): atypical: clozapine (2, 4, 8, IP; n=15), quetiapine (1.25, 2.5, 5, 10, SC; n=23), olanzapine (0.25, 0.5, 1, IP; n=15), ziprasidone (0.625, 1.25, 2.5, IP, n=15); conventional: haloperidol (0.025, 0.05, 0.1, IP, n=15), pimozide (0.125, 0.25, 0.5, IP; n=15), raclopride (0.25, 0.5, 1, SC; n=12), cis-flupenthixol (0.2, 0.4, 0.8, SC; n=15). Values of a and delta were estimated from the response rate functions obtained under each treatment condition, and were compared between drug and vehicle-alone treatments. RESULTS The atypical antipsychotics significantly increased alpha (indicating enhancement of reinforcer efficacy), and also increased delta (indicating reduction of motor capacity). Haloperidol, pimozide and raclopride significantly increased delta; none of the conventional antipsychotics significantly altered alpha. CONCLUSIONS The results extend previous findings with clozapine to other atypical antipsychotics and suggest that enhancement of the efficacy of reinforcers may be a common feature of atypical antipsychotics not shared by conventional antipsychotics.
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Affiliation(s)
- Z Zhang
- Psychopharmacology Section, Division of Psychiatry, Medical School, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK
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Wiley JL, Compton AD. Progressive ratio performance following challenge with antipsychotics, amphetamine, or NMDA antagonists in adult rats treated perinatally with phencyclidine. Psychopharmacology (Berl) 2004; 177:170-7. [PMID: 15243736 PMCID: PMC2637914 DOI: 10.1007/s00213-004-1936-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Accepted: 05/10/2004] [Indexed: 10/26/2022]
Abstract
RATIONALE Previous research has shown that rats exposed perinatally to phencyclidine (PCP) exhibited neuroanatomical abnormalities and altered cognition. In addition to cognitive deficits, schizophrenic patients may also exhibit negative symptoms such as lack of motivation. OBJECTIVES In this study, we used a progressive ratio (PR) schedule of food reinforcement to assess motivation following early exposure to PCP. METHODS Male rat pups were injected SC with 10 mg/kg PCP on postnatal days (PN) 7, 9, and 11. On PN 120, they began training in a PR 5 schedule of food reinforcement. RESULTS Significant PCP effects on acquisition and baseline performance were not noted. After acquisition of the task, challenges with PCP, dizocilpine, amphetamine, haloperidol, and clozapine resulted in dose-dependent decreases in response rates of similar magnitudes in both groups. In rats that continued to respond at higher doses, PCP, dizocilpine, and clozapine failed to alter breakpoints. In contrast, a 5.6 mg/kg dose of amphetamine selectively increased breakpoints in PCP-treated rats, although very few rats responded at this dose. Haloperidol decreased breakpoints in most rats at non-sedating doses. CONCLUSIONS These results suggest that a regimen of perinatal PCP administration sufficient to disrupt cognition did not alter motivation for food reinforcement, regardless of whether rats also received challenges with NMDA antagonists or antipsychotics. Interpretation of amphetamine's high dose effects on breakpoints was complicated by the failure of many rats to respond at this dose. Further research is needed to determine whether negative symptoms such as social withdrawal may be modeled within this neurodevelopmental approach to schizophrenia.
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Affiliation(s)
- Jenny L Wiley
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, PO Box 980613, Richmond, VA 23298-0613, USA.
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Schmadel S, Schwabe K, Koch M. Effects of neonatal excitotoxic lesions of the entorhinal cortex on cognitive functions in the adult rat. Neuroscience 2004; 128:365-74. [PMID: 15350648 DOI: 10.1016/j.neuroscience.2004.07.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/13/2004] [Indexed: 10/26/2022]
Abstract
The entorhinal cortex (EC) is involved in a variety of cognitive functions by virtue of its neuronal input from the neocortex and projection to the hippocampal formation and the limbic-striatal system. Neonatal lesions are increasingly considered useful models for disconnection syndromes such as schizophrenia. Therefore, we investigated the effects of neonatal EC lesions on adult rat behavior. Neonatal (postnatal day 7) lesions were inflicted by bilateral injections of ibotenate into the EC. Sham-lesioned (vehicle injection) and naive (unoperated) rats served as controls. Locomotor activity was measured in prepubertal and young adult rats. Adult rats were then tested for spatial learning in an eight-arm radial maze (reinforced delayed alternation) and for motivation (progressive ratio schedule of operant behavior). Finally, prepulse inhibition (PPI) of the acoustic startle reflex and locomotor activity were investigated with and without apomorphine (APO) challenge. Brain tissue damage was assessed using Nissl-staining. The total volume of the adult rat EC was reduced after neonatal ibotenate-injection. Neonatal EC-lesions increased perseveration only in a delayed task in the radial maze and induced a leftward-shift of breakpoints in operant responding. Lesions did not alter baseline locomotor activity, but enhanced the locomotor stimulating effect of APO. PPI was not affected by neonatal lesions of the EC with and without APO challenge. Neonatal lesions of the EC impaired the ability to hold information during delays and reduced motivation during operant behavior which reflects a state of anhedonia. Thus, they may serve as an animal model for certain aspects of schizophrenia.
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Affiliation(s)
- S Schmadel
- Brain Research Institute, Department of Neuropharmacology, University of Bremen, PO Box 33 04 40, 28334, Germany.
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Schneider M, Koch M. Chronic pubertal, but not adult chronic cannabinoid treatment impairs sensorimotor gating, recognition memory, and the performance in a progressive ratio task in adult rats. Neuropsychopharmacology 2003; 28:1760-9. [PMID: 12888772 DOI: 10.1038/sj.npp.1300225] [Citation(s) in RCA: 339] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
There is evidence from studies in humans and animals that a vulnerable period for chronic cannabinoid administration exists during certain phases of development. The present study tested the hypothesis that long-lasting interference of cannabinoids with the developing endogenous cannabinoid system during puberty causes persistent behavioral alterations in adult rats. Chronic treatment with the synthetic cannabinoid agonist WIN 55,212-2 (WIN) (1.2 mg/kg) or vehicle was extended over 25 days either throughout the rats' puberty or for a similar time period in adult rats. The rats received 20 injections intraperitoneally (i.p.), which were not delivered regularly. Adult rats were tested for object recognition memory, performance in a progressive ratio (PR) operant behavior task, locomotor activity, and prepulse inhibition (PPI) of the acoustic startle response (ASR). PPI was significantly disrupted only by chronic peripubertal cannabinoid treatment. This long-lasting PPI deficit was reversed by the acute administration of the dopamine antagonist haloperidol. Furthermore, we found deficits in recognition memory of pubertal-treated rats and these animals showed lower break points in a PR schedule, whereas food preference and locomotion were not affected. Adult chronic cannabinoid treatment had no effect on the behaviors tested. Therefore, we conclude that puberty in rats is a vulnerable period with respect to the adverse effects of cannabinoid treatment. Since PPI deficits, object recognition memory impairments, and anhedonia/avolition are among the endophenotypes of schizophrenia, we propose chronic cannabinoid administration during pubertal development as an animal model for some aspects of the etiology of schizophrenia.
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Affiliation(s)
- Miriam Schneider
- Brain Research Institute, Department of Neuropharmacology, University of Bremen, Bremen, Germany.
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