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Farhan M, Haleem DJ. Anxiolytic profile of fluoxetine as monitored following repeated administration in animal rat model of chronic mild stress. Saudi Pharm J 2016; 24:571-578. [PMID: 27752230 PMCID: PMC5059824 DOI: 10.1016/j.jsps.2015.03.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Accepted: 03/13/2015] [Indexed: 11/30/2022] Open
Abstract
Background: Fluoxetine, a selective serotonin re-uptake inhibitor (SSRI), has been proposed to be more effective as an antidepressive drug as compared to other SSRIs. After chronic SSRI administration, the increase in synaptic levels of 5-HT leads to desensitization of somatodentritic 5-HT autoreceptors in the raphe nuclei. Chronic stress may alter behavioral, neurochemical and physiological responses to drug challenges and novel stressors. Methods: Twenty four male rats were used in this study. Animals of CMS group were exposed to CMS. Animals of stressed and unstressed group were administrated with fluoxetine at dose of 1.0 mg/kg s well as 5.0 mg/kg repeatedly for 07 days 1 h before exposed to CMS. The objective of the present study was to evaluate that repeated treatment with fluoxetine could attenuate CMS-induced behavioral deficits. Results: Treatment with fluoxetine attenuated CMS-induced behavioral deficits. Fluoxetine administration induced hypophagia in unstressed as well as CMS rats. Acute and repeated administration of fluoxetine increased motor activity in familiar environment but only repeated administration increased exploratory activity in open field. Anxiolytic effects of fluoxetine were greater in unstressed rats. These anxiolytic effects were produced as result of repeated administration not on acute administration of fluoxetine at 1.0 mg/kg as well as 5.0 mg/kg. Conclusion: The present study demonstrated that CMS exposure resulted into behavioral deficits and produced depressive-like symptoms. Fluoxetine, an SSRI, administration attenuated behavioral deficits induced by CMS. Anxiolytic effects of repeated fluoxetine administration were greater in unstressed than CMS animals.
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Affiliation(s)
- Muhammad Farhan
- Neurochemistry and Biochemical Neuropharmacology Research Unit, Department of Biochemistry, University of Karachi, Karachi, Pakistan
| | - Darakshan Jabeen Haleem
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
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2
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Jung E, Kang YP, Yoon IS, Kim JS, Kwon SW, Chung SJ, Shim CK, Kim DD. Effect of permeation enhancers on transdermal delivery of fluoxetine: in vitro and in vivo evaluation. Int J Pharm 2013; 456:362-9. [PMID: 24012861 DOI: 10.1016/j.ijpharm.2013.08.080] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 08/24/2013] [Accepted: 08/28/2013] [Indexed: 12/01/2022]
Abstract
The aim of this study was to investigate the feasibility of transdermal fluoxetine (FX) delivery. The effects of chemical forms (base or salt) and permeation enhancers on in vitro skin permeation of FX were assessed using hairless mouse, rat and human cadaver skin. The optimized formulations from the in vitro studies were then evaluated in an in vivo pharmacokinetic study in rats. The in vitro skin permeation studies suggested that the FX base (FXB) and isopropyl myristate (IPM)-limonene mixture could be suitable for transdermal delivery of FX. The permeation parameters of FX through human cadaver skin were well correlated with that through hairless mouse and rat skin, suggesting that these animal models can be used for predicting the permeability of FX through human skin. After transdermal administration of FX with IPM or the IPM-limonene mixture to rats, the mean steady-state plasma concentration (Css) was 66.20 or 77.55 ng/mL, respectively, which was maintained over 36 h and had a good correlation with the predicted Css from the in vitro data. These in vitro and in vivo data demonstrated that permeation enhancers could be a potential strategy for transdermal delivery of FX.
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Affiliation(s)
- Eunjae Jung
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 151-742, Republic of Korea
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3
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Jeong I, Choi JS, Hahn SJ. Effects of fluoxetine on cloned Kv4.3 potassium channels. Brain Res 2013; 1500:10-8. [DOI: 10.1016/j.brainres.2013.01.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 01/16/2013] [Indexed: 11/28/2022]
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Miryala CSJ, Maswood N, Uphouse L. Fluoxetine prevents 8-OH-DPAT-induced hyperphagia in Fischer inbred rats. Pharmacol Biochem Behav 2011; 98:311-5. [PMID: 21281662 DOI: 10.1016/j.pbb.2011.01.014] [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] [Received: 07/14/2010] [Revised: 12/13/2010] [Accepted: 01/21/2011] [Indexed: 10/18/2022]
Abstract
Ovariectomized, Fischer rats were hormonally primed with 10 μg estradiol benzoate and 50 μg progesterone or were treated with the sesame seed oil vehicle. Food intake was measured 2 h and 24 h after treatment with 0.25 mg/kg of the 5-HT(1A) receptor agonist, (±)-8-hydroxy 2-(di-n-propylamino) tetralin (8-OH-DPAT), 5 mg/kg of the selective serotonin reuptake inhibitor, fluoxetine, or their combination. Consistent with prior studies, two hour food intake of rats given fluoxetine and 8-OH-DPAT did not differ from vehicle controls. 8-OH-DPAT-induced hyperphagia, evident at 2 h, was blocked by co-treatment with fluoxetine. However, in contrast to prior studies, 5 mg/kg fluoxetine, alone, had only modest effects on food intake. Differences in our experimental protocols and/or the strain of rat may account for the lower anorectic response to fluoxetine. Nevertheless, the absence of a significant response to fluoxetine, alone, coupled with the drug's attenuation of the hyperphagic effect of 8-OH-DPAT, leads to the suggestion that the behavioral response to the combined treatment is more complex than that of simple additivity. Consistent with this suggestion, 24 h food intake of rats given 8-OH-DPAT and fluoxetine was lower than that of vehicle or 8-OH-DPAT-treated rats.
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Honig G, Jongsma ME, van der Hart MCG, Tecott LH. Chronic citalopram administration causes a sustained suppression of serotonin synthesis in the mouse forebrain. PLoS One 2009; 4:e6797. [PMID: 19710918 PMCID: PMC2728775 DOI: 10.1371/journal.pone.0006797] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 08/04/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Serotonin (5-HT) is a neurotransmitter with important roles in the regulation of neurobehavioral processes, particularly those regulating affect in humans. Drugs that potentiate serotonergic neurotransmission by selectively inhibiting the reuptake of serotonin (SSRIs) are widely used for the treatment of psychiatric disorders. Although the regulation of serotonin synthesis may be an factor in SSRI efficacy, the effect of chronic SSRI administration on 5-HT synthesis is not well understood. Here, we describe effects of chronic administration of the SSRI citalopram (CIT) on 5-HT synthesis and content in the mouse forebrain. METHODOLOGY/PRINCIPAL FINDINGS Citalopram was administered continuously to adult male C57BL/6J mice via osmotic minipump for 2 days, 14 days or 28 days. Plasma citalopram levels were found to be within the clinical range. 5-HT synthesis was assessed using the decarboxylase inhibition method. Citalopram administration caused a suppression of 5-HT synthesis at all time points. CIT treatment also caused a reduction in forebrain 5-HIAA content. Following chronic CIT treatment, forebrain 5-HT stores were more sensitive to the depleting effects of acute decarboxylase inhibition. CONCLUSIONS/SIGNIFICANCE Taken together, these results demonstrate that chronic citalopram administration causes a sustained suppression of serotonin synthesis in the mouse forebrain. Furthermore, our results indicate that chronic 5-HT reuptake inhibition renders 5-HT brain stores more sensitive to alterations in serotonin synthesis. These results suggest that the regulation of 5-HT synthesis warrants consideration in efforts to develop novel antidepressant strategies.
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Affiliation(s)
- Gerard Honig
- Neuroscience Graduate Program, University of California San Francisco, San Francisco, CA, USA.
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6
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Maswood N, Sarkar J, Uphouse L. Modest effects of repeated fluoxetine on estrous cyclicity and sexual behavior in Sprague Dawley female rats. Brain Res 2008; 1245:52-60. [PMID: 18929547 PMCID: PMC2760087 DOI: 10.1016/j.brainres.2008.09.063] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Revised: 09/01/2008] [Accepted: 09/23/2008] [Indexed: 11/23/2022]
Abstract
In an earlier study, we reported that daily fluoxetine treatment (10 mg/kg/day) rapidly disrupted estrous cyclicity and sexual receptivity in adult, regularly cycling Fischer rats. The current study was designed to investigate if comparable fluoxetine treatment would similarly affect intact, regularly cycling Sprague Dawley rats. In the first experiment, fluoxetine was injected for 24 days. After 11-14 days of daily fluoxetine treatment, 40% of the rats showed a transient disturbance of the estrous cycle with elimination of sexual receptivity. In these affected rats, reduced sexual receptivity generally preceded disruption of vaginal cyclicity. In a second experiment, a shorter exposure was used to attempt to dissociate effects of fluoxetine on behavior and estrous cyclicity. Nine days of fluoxetine treatment eliminated sexual receptivity and proceptivity (hops/darts) in 40% and 46%, respectively, of rats without altering the estrous cycle. Female rats then received a 10th fluoxetine injection 30 min prior to assessment of sexual motivation (measured with the male preference paradigm). There was no effect of fluoxetine on male preference, but fluoxetine significantly reduced the number of crossings and seconds of grooming during preference testing. Therefore, effects of fluoxetine on estrous cyclicity and behavior of Sprague Dawley female rats were smaller and required longer to develop than previously reported in Fischer female rats. These findings reinforce a probable relationship between fluoxetine's effect on sexual activity and neuroendocrine disturbances and illustrate the importance of strain selection in attempting to model human disease.
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Affiliation(s)
| | | | - Lynda Uphouse
- Department of Biology, P.O. Box 425799, Texas Woman’s University, Denton, TX 76204
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7
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Sarkar J, Hiegel C, Maswood N, Uphouse L. Daily male exposure attenuates estrous cycle disruption by fluoxetine. Behav Brain Res 2007; 189:83-91. [PMID: 18243351 DOI: 10.1016/j.bbr.2007.12.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 12/10/2007] [Accepted: 12/17/2007] [Indexed: 10/22/2022]
Abstract
Fluoxetine (Prozac) produces sexual dysfunction in a substantial number of patients. In the few animal studies designed to address this sexual dysfunction in females, data have been inconsistent. Some investigators report that the drug disrupts sexual behavior without affecting the estrous cycle while we have reported robust effects of fluoxetine on the estrous cycle. The current studies were designed to initiate examination of procedural differences that may account for these contradictory outcomes. In the first experiment, intact, regularly cycling female rats were injected daily for 10 days with 10 mg/kg fluoxetine (intraperitoneally) or vehicle. Male-exposed, fluoxetine- or vehicle-treated rats were housed in a room with males and placed for 5 min/day into a male's cage. Other fluoxetine-treated females were housed in a room separate from males. In the second experiment, this protocol was repeated for 20 days and an additional group of females were exposed to male bedding for 5 min/day. Without male exposure, fluoxetine rapidly disrupted vaginal estrus and sexual receptivity so that approximately 50% of the rats failed to show vaginal estrus during the first 5 days; and the majority of the rats had a blocked cycle by 10 days of treatment. With male exposure, these reproductive effects were attenuated. The majority of rats cycled normally during the first 5 days of treatment and more than half cycled throughout the experiment. Loss of behavioral receptivity occurred even when normal estrous cyclicity was present. Although exposure to the male's bedding may have delayed the onset of estrous cycle disruption, five min daily exposure to a male's bedding did not prevent the disruptive effects of fluoxetine. These findings are consistent with evidence that fluoxetine's effect on female sexual dysfunction may result, in part, from the drugs' disruption of the hypothalamic-pituitary-gonadal axis. However, the data also evidence dissociation between the effects of fluoxetine on vaginal and behavioral estrus. These findings may also explain why different laboratories have reported the presence or absence of estrous cycle disturbances following daily treatment with fluoxetine.
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Affiliation(s)
- Jhimly Sarkar
- Department of Biology, P.O. Box 425799, Texas Woman's University, Denton, TX 76204, United States
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8
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Wyneken U, Sandoval M, Sandoval S, Jorquera F, González I, Vargas F, Falcon R, Monari M, Orrego F. Clinically relevant doses of fluoxetine and reboxetine induce changes in the TrkB content of central excitatory synapses. Neuropsychopharmacology 2006; 31:2415-23. [PMID: 16554746 DOI: 10.1038/sj.npp.1301052] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have studied the effect of low doses of two widely used antidepressants, fluoxetine (Flx) and reboxetine (Rbx), on excitatory synapses of rat brain cortex and hippocampus. After 15 days of Flx treatment (0.67 mg/kg/day), its plasma level was 20.7+/-5.6 ng/ml. Analysis of postsynaptic densities (PSDs) by immunoblotting revealed no changes in the glutamate receptor subunits GluR1, NR1, NR2A/B, mGluR1alpha nor in the neurotrophin receptor p75(NTR). However, the brain-derived neurotrophic factor (BDNF) receptor TrkB decreased by 42.8+/-6%, and remained decreased after 6 weeks of treatment. The BDNF and TrkB content in homogenates of cortex and hippocampus began to rise at 9 and 15 days, respectively, and remained high for up to 6 weeks. Similar results were obtained following chronic Rbx administration at 0.128 mg/kg/day. We propose that BDNF, whose synthesis is increased by antidepressants, and which is in part released at synaptic sites, binds to TrkB in PSDs, leading to the internalization of the BDNF-TrkB complex and, thus, to a decrease of TrkB in the PSDs. This was paralleled by greater levels of phosphorylated (ie activated) TrkB in the light membrane fraction, that contains signaling endosomes. The retrograde transport of endocyted BDNF/TrkB complexes from spines to cell bodies, where it activates the synthesis of more BDNF, is a protracted process, potentially requiring several cycles of TrkB/BDNF complex endocytosis and transport. This positive feedback mechanism may help explain the time-lag between drug administration and its therapeutic effect, that is, the antidepressant drug paradox.
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Affiliation(s)
- Ursula Wyneken
- Neuroscience Laboratory, Faculty of Medicine, Universidad de los Andes, Casilla, Santiago, Chile
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9
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Uphouse L, Hensler JG, Sarkar J, Grossie B. Fluoxetine disrupts food intake and estrous cyclicity in Fischer female rats. Brain Res 2006; 1072:79-90. [PMID: 16423328 DOI: 10.1016/j.brainres.2005.12.033] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 12/03/2005] [Accepted: 12/06/2005] [Indexed: 10/25/2022]
Abstract
Adult, regularly cycling female Fischer rats were injected daily with 10 mg/kg fluoxetine for 12-23 days. In the first experiment, body weight and vaginal smears were monitored daily. Fluoxetine treatment reduced body weight within the first 24 h of treatment. Fluoxetine treatment also elongated the estrous cycle, reduced blood levels of progesterone, and eliminated lordosis behavior. In the second experiment, body weight and food intake were examined and a pair-fed group was included to determine if fluoxetine-induced anorexia contributed to the disturbance of the estrous cycle. In pair-fed rats, effects similar to fluoxetine treatment were present. These results lead to the suggestion that fluoxetine's anorectic properties could disrupt the female's normal endocrine cyclicity and that this disruption could be relevant to the reduction in sexual behavior and motivation. However, when the duration of fluoxetine treatment was extended beyond 16 to 17 days, fluoxetine-treated female rats reinitiated vaginal cyclicity and showed evidence of normal sexual receptivity. In contrast, the estrous cycles of their pair-fed counterparts remained disrupted. Thus, restricted food intake appears to contribute to the disruption of the estrous cycle and elimination of sexual receptivity during fluoxetine treatment. However, compensatory changes in the serotonergic system that are associated with chronic fluoxetine administration may contribute to the gradual recovery of estrous cyclicity and sexual receptivity of the fluoxetine-treated animals.
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Affiliation(s)
- Lynda Uphouse
- Department of Biology, Texas Woman's University, Denton, TX 76204, USA.
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10
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Thompson MR, Li KM, Clemens KJ, Gurtman CG, Hunt GE, Cornish JL, McGregor IS. Chronic fluoxetine treatment partly attenuates the long-term anxiety and depressive symptoms induced by MDMA ('Ecstasy') in rats. Neuropsychopharmacology 2004; 29:694-704. [PMID: 14627999 DOI: 10.1038/sj.npp.1300347] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Use of the drug 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy') can have long-term adverse effects on emotion in both humans and laboratory animals. The present study examined whether chronic treatment with the antidepressant drug fluoxetine could reverse such effects. Male Wistar rats were briefly exposed to MDMA (4 x 5 mg/kg over 4 h) or vehicle on 2 consecutive days. Approximately 9-12 weeks later, half of the rats received a dose of approximately 6 mg/kg/day fluoxetine in their drinking water for a 5-week period. Fluoxetine administration reduced fluid intake and body weight in MDMA and vehicle pretreated rats. After several weeks of fluoxetine treatment, rats were assessed on the social interaction test, the emergence test of anxiety and the forced swim model of depression. MDMA pretreated rats showed reduced social interaction, increased anxiety on the emergence test, and increased immobility and decreased active responses in the forced swim test. Fluoxetine treatment reversed MDMA-induced anxiety in the emergence test and depressive-like effects in the forced swim test, yet exhibited no effects on the social interaction test. MDMA pretreated rats had decreased 5-HT and 5-HIAA levels in limbic and cortical regions, and decreased density of serotonin transporter sites in the cortex. Fluoxetine treatment did not greatly affect 5-HT levels in MDMA pretreated rats, but significantly decreased 5-HIAA levels in all brain sites examined. Postmortem blood serum levels of fluoxetine and norfluoxetine did not differ in MDMA and vehicle pretreated rats. These results indicate that fluoxetine may provide a treatment option for some of the deleterious long-term effects resulting from MDMA exposure.
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Kishimoto W, Hiroi T, Shiraishi M, Osada M, Imaoka S, Kominami S, Igarashi T, Funae Y. Cytochrome P450 2D catalyze steroid 21-hydroxylation in the brain. Endocrinology 2004; 145:699-705. [PMID: 14563706 DOI: 10.1210/en.2003-1109] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
mRNA of cytochrome P450 21-hydroxylase (P450c21) is expressed in the brain, but little is known about the enzymatic properties of P450c21 in the brain. In the present study, we showed, by using various recombinant cytochrome P450 (CYP)2D enzymes and anti-CYP2D4- or P450c21-specific antibodies, that rat brain microsomal steroid 21-hydroxylation is catalyzed not by P450c21, but by CYP2D isoforms. Rat CYP2D4 and human CYP2D6, which are the predominant CYP2D isoforms in the brain, possess 21-hydroxylation activity for both progesterone and 17alpha-hydroxyprogesterone. In rat brain microsomes, these activities were not inhibited by anti-P450c21 antibodies, but they were effectively inhibited by the CYP2D-specific chemical inhibitor quinidine and by anti-CYP2D4 antibodies. mRNA and protein of CYP2D4 were expressed throughout the brain, especially in cerebellum, striatum, pons, and medulla oblongata, whereas the mRNA and protein levels of P450c21 were extremely low or undetectable. These results support the idea that CYP2D4, not P450c21, works as steroid 21-hydroxylase in the brain. Allopregnanolone, a representative gamma-aminobutyric acid receptor modulator, was also hydroxylated at the C-21 position by recombinant CYP2D4 and CYP2D6. Rat brain microsomal allopregnanolone 21-hydroxylation was inhibited by fluoxetine with an IC(50) value of 2 microm, suggesting the possibility that the brain CYP2D isoforms regulate levels of neurosteroids such as allopregnanolone, and that this regulation is modified by central nervous system-active drugs such as fluoxetine.
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Affiliation(s)
- Wataru Kishimoto
- Department of Chemical Biology, Osaka City University Medical School, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan
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12
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Tao R, Fray A, Aspley S, Brammer R, Heal D, Auerbach S. Effects on serotonin in rat hypothalamus of D-fenfluramine, aminorex, phentermine and fluoxetine. Eur J Pharmacol 2002; 445:69-81. [PMID: 12065196 DOI: 10.1016/s0014-2999(02)01751-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Hypothalamic 5-HT (serotonin) regulates food intake, energy expenditure and bodyweight. Using in vivo microdialysis, we determined the effects of various anorectic drugs on hypothalamic extracellular 5-HT levels during the dark phase when rats predominantly feed. Phentermine and aminorex, which were originally considered to be catecholaminergic drugs, markedly increased 5-HT efflux in rat hypothalamus. Their actions were less profound than D-fenfluramine, but considerably greater than that of the selective 5-HT reuptake inhibitor, fluoxetine. This suggests that enhanced hypothalamic 5-HT function could be involved in their anorectic actions. Pharmacological characterization revealed that D-fenfluramine, aminorex and probably also phentermine potentiate synaptic 5-HT function predominantly by release, whereas fluoxetine acts exclusively by reuptake inhibition. The results also revealed that the combined actions of phentermine and D-fenfluramine on hypothalamic extracellular 5-HT levels were additive, but not synergistic. In contrast, there was a significant negative cooperative effect on extraneuronal 5-HT of combining phentermine with fluoxetine.
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Affiliation(s)
- Rui Tao
- Nelson Laboratories, Department of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ 08854-8082, USA
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13
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Norrholm SD, Ouimet CC. Chronic fluoxetine administration to juvenile rats prevents age-associated dendritic spine proliferation in hippocampus. Brain Res 2000; 883:205-15. [PMID: 11074049 DOI: 10.1016/s0006-8993(00)02909-7] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The density of dendritic spines, the postsynaptic sites of most excitatory synapses, increases during the first 2 postnatal months in rat hippocampus. Significant alterations in hippocampal levels of serotonin and norepinephrine impact synaptic development during this time period. In the present study, dendritic spine density was studied in the hippocampus (CA1) and dentate gyrus of juvenile rats acutely and chronically exposed to antidepressant drugs that act on serotonin and norepinephrine. One group of 21-day-old rats was given a single injection of a serotonin specific re-uptake inhibitor (fluoxetine or fluvoxamine), a norepinephrine-specific re-uptake inhibitor (desipramine), or saline and killed after 24 h. A second group of rats was injected daily, beginning on postnatal day (PN) 21, for 3 weeks. This group was further subdivided into rats that were killed 1 day or 21 days after the last injection. Golgi analysis showed that a single injection of fluvoxamine produced a significant increase in dendritic spine density in stratum radiatum of CA1 and in the dentate gyrus. Further, acute treatment with all three antidepressants increased the total length of secondary dendrites in CA1, with fluoxetine and desipramine increasing the number of secondary dendrites as well. In fluoxetine-treated animals killed on days 42 or 62 (1 or 21 days post-treatment, respectively), dendritic spine density remained at levels present in CA1 at 21 days. These results show that acute antidepressant treatment can impact dendritic length and spine density, and raise the possibility that chronic fluoxetine treatment arrests spine development into young adulthood.
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Affiliation(s)
- S D Norrholm
- Program in Neuroscience, Department of Psychology, Florida State University, 211 Biomedical Research Facility, Tallahassee, FL 32306-4340, USA
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Harvey BH, Bouwer CD. Neuropharmacology of paradoxic weight gain with selective serotonin reuptake inhibitors. Clin Neuropharmacol 2000; 23:90-7. [PMID: 10803799 DOI: 10.1097/00002826-200003000-00006] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
It has been suggested that weight gain associated with tricyclic antidepressants (TCA) reflect actions on dopamine (DA) and histamine receptors. However, a definitive cause is purely assumptive given the nonselective pharmacology of these agents. The selective serotonin reuptake inhibitors (SSRIs), as well as agents like dexfenfluramine (DFF), have emphasized the pivotal role of serotonin (5HT) in reducing carbohydrate (CHO) intake, and have provided a more selective tool with which to study appetite regulation. It would be expected that all SSRIs should exert a similar anorectic action. However, recent reports provide evidence to the contrary. Despite their claimed selectivity, SSRIs still interact, either directly or indirectly, with various critical neurotransmitter systems. In addition, although the anorectic action of fluoxetine (FLX) is well recognized, long-term follow-up studies in depressed patients and in obese nondepressed patients reveal that its weight-reducing effects are transient, even leading to a gain in body weight. Similarly, paroxetine (PRX) and citalopram (CTP) have also been associated with weight gain. These latter observations are unexpected because PRX and CTP are highly potent and selective SSRIs. A neuropharmacologic rationale for the apparent paradoxic effects of SSRIs on appetite not a review of neuronal regulation of appetite is presented in this article. As with the regulation of feeding, paradoxic weight gain observed with SSRIs appears to rest on the interaction of 5HT with multiple mechanisms, with the extent of weight gain observed being dependent on subtle, yet important pharmacologic differences within the group. Finally, the neurobiology of depressive illness itself, and of recovery from it, is a major contributing factor to individual response to these drugs.
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Affiliation(s)
- B H Harvey
- Department of Pharmacology, Potchefstroom University for Christian Higher Education, South Africa
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15
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Freo U, Ori C, Dam M, Merico A, Pizzolato G. Effects of acute and chronic treatment with fluoxetine on regional glucose cerebral metabolism in rats: implications for clinical therapies. Brain Res 2000; 854:35-41. [PMID: 10784104 DOI: 10.1016/s0006-8993(99)02261-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The wide therapeutic spectrum of fluoxetine (e.g., antidepressant, antipanic, antiphobic, antiobsessive, analgesic, antimigraine) requires long-term administration and adaptive changes. To test whether adaptation involves the serotonin (5-HT) transporters, we measured the effects of fluoxetine on the regional cerebral metabolic rate for glucose (rCMRglc) in control rats or in rats pretreated for 2 weeks with fluoxetine (8 mg/kg, i.p., daily, 2 days wash out); rCMRglc was measured in 56 brain regions, using the quantitative [14C]deoxyglucose technique, at 30 min after i.p. administration of fluoxetine 0.4, 4 or 40 mg/kg, i.p., to non-pretreated rats or fluoxetine 4 mg/kg to pretreated rats. In non-pretreated rats, fluoxetine reduced rCMRglc in a dose-dependent fashion in 4 (7%, mean decrease 11%), 28 (50%, mean decrease 23%) and 37 (66%, mean decrease 32%) brain regions. In chronic fluoxetine-pretreated rats, fluoxetine decreased rCMRglc to a substantially lesser degree (eight regions, 14%; mean decrease, 10%). Subcortical brain regions (i.e., hypothalamic paraventricular, locus coeruleus and basal ganglia nuclei) that mediate the physiological responses to stress were very sensitive to fluoxetine acutely and subsensitive after chronic treatment. As kinetic tolerance to fluoxetine does not occur during chronic administration, the diminished rCMRglc responsivity to fluoxetine reflects dynamic, adaptive tolerance of 5-HT transporters and, consequently, increased synaptic 5-HT concentrations; the findings suggest that fluoxetine may be therapeutic by increasing the 5-HT-negative modulation upon areas that drive the abnormally hyperactive responses to stress found in several neuropsychiatric conditions.
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Affiliation(s)
- U Freo
- Department of Neurology, University of Padova, Padua, Italy
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16
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Yamada J, Sugimoto Y, Inoue K. Selective serotonin reuptake inhibitors fluoxetine and fluvoxamine induce hyperglycemia by different mechanisms. Eur J Pharmacol 1999; 382:211-5. [PMID: 10556672 DOI: 10.1016/s0014-2999(99)00593-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effects of the selective serotonin reuptake inhibitors, fluoxetine and fluvoxamine, on plasma glucose levels were investigated in mice. Both fluoxetine and fluvoxamine elicited significant hyperglycemia, while a selective noradrenaline reuptake inhibitor maprotiline had no effect. Fluoxetine and fluvoxamine did not change serum insulin levels, although they elicited hyperglycemia. Pretreatment with the serotonin (5-hydroxytryptamine, 5-HT) depleter, p-chlorophenylalanine (pCPA), abolished fluvoxamine-induced hyperglycemia, although pCPA did not affect the fluoxetine-induced glycemic effects. These results suggest that the selective serotonin reuptake inhibitors fluoxetine and fluvoxamine induce hyperglycemia by inhibition of insulin release. Moreover, our findings indicate that the glycemic effects of these drugs are differentially associated with serotonergic mechanisms.
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Affiliation(s)
- J Yamada
- Department of Pharmacology, Kobe Pharmaceutical University, Motoyamakita-machi, Higashinada-ku, Kobe, Japan.
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17
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Trillat AC, Malagié I, Mathe-Allainmat M, Anmella MC, Jacquot C, Langlois M, Gardier AM. Synergistic neurochemical and behavioral effects of fluoxetine and 5-HT1A receptor antagonists. Eur J Pharmacol 1998; 357:179-84. [PMID: 9797034 DOI: 10.1016/s0014-2999(98)00590-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We studied the ability of WAY 100635 [N-[4-(2-methoxyphenyl)-1-piperazinyl]-N-(2-pyridinyl) cyclo-hexanecarboxamide], 0.5 mg/kg, i.v. and (-)-5-Me-8-OH-DPAT [(-)-5-methyl-8-hydroxy-2-(di-n-propylamino)tetralin], 3 mg/kg, i.v. two selective 5-HT1A receptor antagonists, to potentiate: (1) the enhancement of extracellular 5-HT levels ([5-HT(ext)]) induced by a single administration of 5 mg/kg i.p. fluoxetine using in vivo microdialysis in the ventral hippocampus of conscious rats, (2) the decrease in food intake induced by this antidepressant drug in food-deprived rats. The effects of fluoxetine were significantly potentiated, by 30-40%, by WAY 100635 as well as by (-)-5-Me-8-OH-DPAT in the two sets of experiments. Thus, fluoxetine increased [5-HT(ext)] in serotonergic nerve terminal areas and consequently, induced hypophagia, both effects being limited by indirect activation of somatodendritic 5-HT1A autoreceptors.
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Affiliation(s)
- A C Trillat
- Laboratoire de Neuropharmacologie UPRES JEMESR 92-372, Institut de Signalisation et Innovation Thérapeutique (IFR-ISIT), Université Paris Sud, Châtenay-Malabry, France.
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18
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Heal DJ, Cheetham SC, Prow MR, Martin KF, Buckett WR. A comparison of the effects on central 5-HT function of sibutramine hydrochloride and other weight-modifying agents. Br J Pharmacol 1998; 125:301-8. [PMID: 9786502 PMCID: PMC1565620 DOI: 10.1038/sj.bjp.0702067] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Effects on 5-HT function of sibutramine and its active metabolites, BTS 54 354 and BTS 54 505, were compared with fluoxetine, (+)-fenfluramine and (+)-amphetamine. 2. In vitro sibutramine weakly inhibited [3H]-5-HT uptake into brain synaptosomes. BTS 54 354, BTS 54 505 and fluoxetine were powerful [3H]-5-HT uptake inhibitors, whereas (+)-fenfluramine and (+)-amphetamine were very much weaker. Conversely, whilst sibutramine, its metabolites and fluoxetine did not release [3H]-5-HT from brain slices at < or = 10(-5)M, (+)-fenfluramine and (+)-amphetamine concentration-dependently increased [3H]-5-HT release. 3. Sibutramine and fluoxetine had no effect on 5-hydroxytryptophan (5-HTP) accumulation in either frontal cortex or hypothalamus at doses < 10 mg kg(-1). In contrast, (+)-amphetamine ( > or = 3 mg kg(-1)) reduced 5-HTP in hypothalamus, whilst (+)-fenfluramine (> or =1 mg kg(-1)) decreased 5-HTP in both regions. 4. Sibutramine (10 mg kg(-1) i.p.) and fluoxetine (10 mg kg(-1) i.p.) produced slow, prolonged increases of extracellular 5-HT in the anterior hypothalamus. In contrast, (+)-fenfluramine (3 mg kg(-1) i.p.) and (+)-amphetamine (4 mg kg(-1) i.p.) induced rapid, short-lasting increases in extracellular 5-HT. 5. Only (+)-fenfluramine (10 mg kg(-1)) altered 5-HT2A receptors in rat frontal cortex when given for 14 days, producing a 61% reduction in receptor number and a 18% decrease in radioligand affinity. 6. These results show that sibutramine powerfully enhances central 5-HT function via its secondary and primary amine metabolites; this effect, like that of fluoxetine, is almost certainly mediated through 5-HT uptake inhibition. By contrast, (+)-fenfluramine enhances 5-HT function predominantly by increasing 5-HT release. (+)-Amphetamine, though weaker than (+)-fenfluramine, also enhances 5-HT function by release.
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Affiliation(s)
- D J Heal
- Knoll Pharmaceuticals Research & Development, Nottingham
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19
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Caccia S, Confalonieri S, Bergami A, Fracasso C, Anelli M, Garattini S. Neuropharmacological effects of low and high doses of repeated oral dexfenfluramine in rats: a comparison with fluoxetine. Pharmacol Biochem Behav 1997; 57:851-6. [PMID: 9259015 DOI: 10.1016/s0091-3057(96)00322-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The neuropharmacological effects of repeated oral doses of dexfenfluramine (DF; 1.25-10 mg/kg, twice daily for 21 days) were examined in rats and related to the drug brain levels. Results were compared with fluoxetine (FL) given at similar doses relative to its anorectic ED50. Both drugs dose-dependently slowed body weight gain and reduced brain serotonin (5-HT). However, at 1.25 mg/kg DF caused only a slight and transient decrease in cortical 5-HT. Comparable doses of FL (6.25-12.5 mg/kg) lowered 5-HT more than DF, besides slightly reducing striatal dopamine. At higher doses DF markedly reduced 5-HT in all regions, and to a lesser extent noradrenaline in hippocampus. There was a negative relationship between 5-HT and log total active drug levels and the indole was approximately halved at drug levels about 50 times lower with DF than FL. However, the ratio between drug levels causing marked 5-HT reductions and those considered anorectic was similar for DF and FL because brain levels at the anorectic ED50 were higher with FL than DF. Long-lasting reductions of 5-HT were also observed but recovery was only consistently slow beginning from 5 mg/ kg DF. Comparable doses of FL could not be used because its general toxicity leads to the death of rats after only 2-4 multiples of its anorectic ED50.
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Affiliation(s)
- S Caccia
- Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy
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20
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21
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Clifton PG, Lee MD. Fluoxetine hypophagia. Is there a role for serotonergic mechanisms in some circumstances? Trends Pharmacol Sci 1997; 18:191-2. [PMID: 9226996 DOI: 10.1016/s0165-6147(97)90620-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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22
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Curzon G, Gibson EL, Oluyomi AO. Appetite suppression by commonly used drugs depends on 5-HT receptors but not on 5-HT availability. Trends Pharmacol Sci 1997; 18:21-5. [PMID: 9114726 DOI: 10.1016/s0165-6147(96)01003-6] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The widely prescribed appetite suppressants D-fenfluramine and fluoxetine not only decrease feeding and body weight but also increase extracellular brain 5-HT. As central injection of 5-HT also decreases feeding, the drugs are often thought to require an increase of 5-HT at receptors in order to exert their hypophagic effect. However, much evidence now suggests that D-fenfluramine and its metabolite D-norfenfluramine can cause hypophagia by acting directly at unspecified 5-HT receptors and at 5-HT2C receptors, respectively, while fluoxetine may act independently of 5-HT receptors. These hypophagias may involve interference with the hyperphagic action of neuropeptide Y.
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Affiliation(s)
- G Curzon
- Institute of Neurology, London, UK
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23
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Uzunov DP, Cooper TB, Costa E, Guidotti A. Fluoxetine-elicited changes in brain neurosteroid content measured by negative ion mass fragmentography. Proc Natl Acad Sci U S A 1996; 93:12599-604. [PMID: 8901628 PMCID: PMC38038 DOI: 10.1073/pnas.93.22.12599] [Citation(s) in RCA: 271] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Fluoxetine administered intraperitoneally to sham-operated or adrenalectomized/castrated (ADX/CX) male rats dose-dependently (2.9-58 mumol/kg i.p.) increased the brain content of the neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone, 3 alpha, 5 alpha-TH PROG). The increase of brain 3 alpha, 5 alpha-TH PROG content elicited by 58 mumol/kg fluoxetine lasted more than 2 hr and the range of its extent was comparable in sham-operated (approximately 3-10 pmol/g) and ADX/CX rats (2-9 pmol/g) and was associated with a decrease (from 2.8 to 1.1 pmol/g) in the 5 alpha-pregnan-3,20-dione (5 alpha-dihydroprogesterone, 5 alpha-DH PROG) content. The pregnenolone, progesterone, and dehydroepiandrosterone content failed to change in rats receiving fluoxetine. The extent of 3 alpha, 5 alpha-TH PROG accumulation elicited by fluoxetine treatment differed in various brain regions, with the highest increase occurring in the olfactory bulb. Importantly, fluoxetine failed to change the 3 alpha, 5 alpha-TH PROG levels in plasma, which in ADX/CX rats were at least two orders of magnitude lower than in the brain. Two other serotonin re-uptake inhibitors, paroxetine and imipramine, in doses equipotent to those of fluoxetine in inhibiting brain serotonin uptake, were either significantly less potent than fluoxetine (paroxetine) or failed to increase (imipramine) 3 alpha, 5 alpha-TH PROG brain content. The addition of 10 microM of 5 alpha-DH PROG to brain slices of ADX/CX rats preincubated with fluoxetine (10 microM, 15 min) elicited an accumulation of 3 alpha, 5 alpha-TH PROG greater than in slices preincubated with vehicle. A fluoxetine stimulation of brain 3 alpha, 5 alpha-TH PROG biosynthesis might be operative in the anxiolytic and antidysphoric actions of this drug.
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Affiliation(s)
- D P Uzunov
- Department of Psychiatry, University of Illinois at Chicago 60612, USA
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24
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Invernizzi R, Bramante M, Samanin R. Role of 5-HT1A receptors in the effects of acute chronic fluoxetine on extracellular serotonin in the frontal cortex. Pharmacol Biochem Behav 1996; 54:143-7. [PMID: 8728551 DOI: 10.1016/0091-3057(95)02159-0] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Fluoxetine 10 mg/kg i.p. significantly increased the extracellular concentrations of serotonin (5-HT) in the frontal cortex as assessed by in vivo microdialysis. This effect was significantly potentiated when 0.3 mg/kg s.c. WAY-100635, a 5-HT1A receptor antagonist, was administered 30 min before. WAY-100635 by itself had no effect on extracellular 5-HT. Twenty-four hours after chronic fluoxetine schedule (10 mg/kg/day i.p. x 14 days), basal extracellular 5-HT concentrations in the frontal cortex were higher than those of animals that had received the vehicle chronically. At 24 h after the last dose, a challenge dose of fluoxetine (10 mg/kg i.p.) raised extracellular 5-HT similarly in chronically vehicle or fluoxetine treated rats. At this same interval 25 micrograms/kg s.c. 8-OH-DPAT, a 5-HT1A receptor agonist, significantly reduced extracellular 5-HT only in the frontal cortex of rats treated chronically with the vehicle. Examining basal extracellular 5-HT, the effect of a challenge dose of fluoxetine and the effect of 25 micrograms/kg 8-OH-DPAT after 96 h washout, no differences were found between chronically fluoxetine and vehicle-treated rats. The results confirm that the ability of fluoxetine to stimulate 5-HT1A autoreceptors through an increase of endogenous 5-HT attenuates its effect on cortical dialysate 5-HT. Chronic fluoxetine increased the basal concentrations of extracellular 5-HT only when a substantial amount of its metabolite was present in the brain and during the desensitization of presynaptic 5-HT1A autoreceptors (24 h after the last dose). These effects, in fact, disappeared after 96 h washout. The continuous presence of the drug may, therefore, be necessary to maintain extracellular 5-HT at concentrations high enough to produce a therapeutic effect.
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Affiliation(s)
- R Invernizzi
- Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy
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25
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Fuller RW, Hemrick-Luecke SK, Snoddy HD. Fluoxetine at anorectic doses does not have properties of a dopamine uptake inhibitor. J Neural Transm (Vienna) 1994; 96:165-77. [PMID: 7826568 DOI: 10.1007/bf01294784] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Although fluoxetine is a highly selective inhibitor of serotonin uptake in vitro and in vivo, some investigators have suggested that dopamine uptake inhibition may contribute to anorectic actions of fluoxetine. The present experiments were done to determine fluoxetine's effects in some animal protocols in which dopamine uptake inhibitors have characteristic actions. Mazindol prevented the depletion of striatal dopamine and its metabolites by amphetamine in iprindole-pretreated rats, but fluoxetine had no effect. Mazindol prevented the depletion of striatal dopamine and its metabolites by 6-hydroxydopamine injected intracerebroventricularly into rats, but fluoxetine had no effect. Mazindol enhanced the elevation of 3,4-dihydroxyphenylacetic acid concentration in rat brain after spiperone injection, but fluoxetine did not cause that effect. Fluoxetine did not mimic amfonelic acid in antagonizing the retention of alpha-methyl-m-tyramine invant striatum after the injection of alpha-methyl-m-tyrosine. These results show that fluoxetine, at doses that are effective in blocking the serotonin uptake carrier and causing anorexia, does not block the dopamine uptake carrier.
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Affiliation(s)
- R W Fuller
- Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN
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26
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Souza ME, Polizello AC, Uyemura SA, Castro-Silva O, Curti C. Effect of fluoxetine on rat liver mitochondria. Biochem Pharmacol 1994; 48:535-41. [PMID: 8068040 DOI: 10.1016/0006-2952(94)90283-6] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The in vitro and in vivo effects of fluoxetine (and its active metabolite norfluoxetine) on mitochondrial respiration and F0F1-ATPase were studied, respectively, in mitochondria and submitochondrial particles isolated from rat liver. Fluoxetine in vitro inhibited state 3 mitochondrial respiration for alpha-ketoglutarate and succinate oxidations (50% of effect at 0.25 and 0.35 mM drug concentrations, respectively); stimulated state 4 for succinate; and induced a decrease in the respiratory control ratio (RCR) for both oxidizable substrates. The F0F1-ATPase activity was determined at various pH levels in the absence and presence of Triton X-100. The solubilized form was not affected markedly, but an inhibition, apparently non-competitive, was observed for the membrane-bound enzyme, with 50% of the effect at a 0.06 mM drug concentration in pH 7.4. These results suggest that fluoxetine in vitro acts on F0F1-ATPase through direct interaction with the membrane F0 component (similar to oligomycin), or first with mitochondrial membrane and then affecting F0. A very similar behavior concerning the respiratory parameters and F0F1-ATPase properties was observed with norfluoxetine. The in vivo studies with fluoxetine showed stimulation of mitochondrial respiration in state 4 for alpha-ketoglutarate or succinate oxidations in acute or prolonged treatments (1 hr after a single i.p. dose of 20 mg of drug/kg of body weight, and 22 hr after 12 days of treatment with a daily dose of 10 mg/kg of body weight, respectively), indicating uncoupling of oxidative phosphorylation. Pronounced changes were not observed in the K0.5 values of F0F1-ATPase catalytic sites, but the Vmax decreased during the prolonged treatment. The results show that fluoxetine (as well as norfluoxetine) has multiple effects on the energy metabolism of rat liver mitochondria, being potentially toxic in high doses. The drug effects seem to be a consequence of the drug and/or metabolite solubilization in the inner membrane of the mitochondria.
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Affiliation(s)
- M E Souza
- Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Brasil
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27
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Affiliation(s)
- S Garattini
- Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy
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28
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Gardier AM, Lepoul E, Trouvin JH, Chanut E, Dessalles MC, Jacquot C. Changes in dopamine metabolism in rat forebrain regions after cessation of long-term fluoxetine treatment: relationship with brain concentrations of fluoxetine and norfluoxetine. Life Sci 1994; 54:PL51-6. [PMID: 8289580 DOI: 10.1016/0024-3205(94)00821-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We examined the effects of repeated administration of the selective serotonin uptake inhibitor (SSRI) fluoxetine (Flx) (5, 10, or 15 mg/kg i.p., twice daily for 21 days) on brain and plasma concentrations of the parent drug and its active desmethyl metabolite, norfluoxetine (NFlx), in rats during the 21-day regimen as well as after cessation of drug treatment. We also measured dopamine (DA) levels in 2 midbrain regions (the striatum, St and nucleus accumbens, NAc) in rats killed 1-14 days after the last dose. NFlx concentrations in plasma and brain were ten times higher than those of Flx during the period of drug treatment. Although Flx accumulated more markedly in the rat brain than NFlx, it disappeared completely from plasma and brain after treatment stopped, while NFlx persisted up to Day P7. Chronic Flx treatment caused a persistent decrease in brain DA levels of -60% to -70% in St and NAc; this lasted for 7-14 days after cessation of treatment, depending on the dose used. The levels of DA metabolites decreased by 20-40%, and, except for 3-MT, tended to overshoot during the recovery period. Our data suggest that the long-term inhibition of DA neurons after cessation of Flx treatment parallels the inhibition previously observed for 5-HT neurons. Thus, besides blocking 5-HT uptake, Flx is likely to also inhibit in vivo DA uptake in forebrain regions, following prolonged administration.
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Affiliation(s)
- A M Gardier
- Fac. Pharmacie, Lab. Pharmacol., JE DRED 1992-372, Chatenay-Malabry, France
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Caccia S, Anelli M, Codegoni AM, Fracasso C, Garattini S. The effects of single and repeated anorectic doses of 5-hydroxytryptamine uptake inhibitors on indole levels in rat brain. Br J Pharmacol 1993; 110:355-9. [PMID: 7693282 PMCID: PMC2175989 DOI: 10.1111/j.1476-5381.1993.tb13817.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. The effects of acute and repeated equiactive anorectic doses (ED50) of recently marketed 5-hydroxytryptamine (5-HT) uptake inhibitors on the content of brain indoles were compared in rats in relation to the brain regional concentrations of unchanged drug and its known active metabolite. 2. Single intraperitoneal (i.p.) doses of the anorectic ED50 of fluoxetine (35 mumol kg-1), fluvoxamine (60 mumol kg-1), paroxetine (20 mumol kg-1) and sertraline (49 mumol kg-1) slightly reduced brain 5-hydroxyindoleacetic acid (5-HIAA), with regional differences, this being compatible with 5-HT uptake blockade. Only fluvoxamine and sertraline significantly enhanced the content of 5-HT in the cortex. 3. The regional sensitivity to the acute effect of a given drug was not related to any preferential drug distribution, as these compounds distributed almost uniformly in the brain areas considered (cortex, striatum and hippocampus). 4. Repeating the same doses twice daily, i.p. for 14 days, however gave a different picture, fluvoxamine having little or no effect on the content of indoles and fluoxetine, paroxetine and sertraline lowering both 5-HT and 5-HIAA in all the brain regions compared to pair-fed control animals, 1 h after the last dose. 5. One week later only fluoxetine-treated animals still had reduced brain 5-HT, this probably being related to the accumulation of its main metabolite norfluoxetine in rat brain after chronic dosing. 6. Further studies on the relationship between the long-term neurochemical changes and anorectic activity are required but it appears from these results that anorectic drugs with similar acute effects on 5-HT uptake may differ in their long-term effects on 5-HT mechanisms.
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Affiliation(s)
- S Caccia
- Istituto di Ricerche Farmacologiche, Mario Negri, Milan, Italy
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30
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Anelli M, Bizzi A, Caccia S, Codegoni AM, Fracasso C, Garattini S. Anorectic activity of fluoxetine and norfluoxetine in mice, rats and guinea-pigs. ACTA ACUST UNITED AC 1992; 44:696-8. [PMID: 1359101 DOI: 10.1111/j.2042-7158.1992.tb05500.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The present study aimed to establish the role of the metabolite norfluoxetine in the anorectic activity of fluoxetine, and to relate the anorectic doses (ED50) to the brain concentrations of the parent drug and its metabolite. Fluoxetine showed anorectic activity at increasing intraperitoneal doses (ED50 = 39.1, 34.7 and 21.7 mumol kg-1 in mouse, rat and guinea-pig, respectively) and norfluoxetine was slightly more active (24.3, 22.9 and 19.1 mumol kg-1, respectively) in all three species. In terms of maximum concentration (Cmax) and area under the curve (AUC) within the experimental period (0-90 min), brain concentrations varied widely and were poorly related to the dose; guinea-pig appeared to be much more sensitive to fluoxetine than was mouse or rat. Administered norfluoxetine was present in the brain of the three species in approximately the same order as fluoxetine, i.e. lower in guinea-pig than in mouse or rat. The Cmax and AUC of norfluoxetine after fluoxetine administration was 50-60% of the values after an equiactive dose of norfluoxetine in mouse and guinea-pig, and more than 80% in rat.
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Affiliation(s)
- M Anelli
- Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy
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31
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Affiliation(s)
- S Caccia
- Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy
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