Br J Pharmacol. 2001 Sep;134(1):46-57.
The mechanisms involved in the long-lasting neuroprotective effect of fluoxetine against MDMA ('ecstasy')-induced degeneration of 5-HT nerve endings in rat brain.

Sanchez V, Camarero J, Esteban B, Peter MJ, Green AR, Colado MI.

Departamento de Farmacologia, Facultad de Medicina, Universidad Complutense, Madrid 28040, Spain. Pharmacology Research Group, School of Pharmacy, De Montfort University, Leicester LE1 9BH. AstraZeneca R&D Charnwood, Bakewell Road, Loughborough LE11 5RH.

1. It has been reported that co-administration of fluoxetine with 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') prevents MDMA-induced degeneration of 5-HT nerve endings in rat brain. The mechanisms involved have now been investigated. 2. MDMA (15 mg kg(-1), i.p.) administration produced a neurotoxic loss of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in cortex, hippocampus and striatum and a reduction in cortical [3H]-paroxetine binding 7 days later. 3. Fluoxetine (10 mg kg(-1), i.p., x2, 60 min apart) administered concurrently with MDMA or given 2 and 4 days earlier provided complete protection, and significant protection when given 7 days earlier. Fluvoxamine (15 mg kg(-1), i.p., x2, 60 min apart) only produced neuroprotection when administered concurrently. Fluoxetine (10 mg kg(-1), x2) markedly increased the K(D) and reduced the B(max) of cortical [3H]-paroxetine binding 2 and 4 days later. The B(max) was still decreased 7 days later, but the K(D) was unchanged. [3H]-Paroxetine binding characteristics were unchanged 24 h after fluvoxamine (15 mg kg(-1), x2). 4. A significant cerebral concentration of fluoxetine plus norfluoxetine was detected over the 7 days following fluoxetine administration. The fluvoxamine concentration had decreased markedly by 24 h. 5. Pretreatment with fluoxetine (10 mg kg(-1), x2) failed to alter cerebral MDMA accumulation compared to saline pretreated controls. 6. Neither fluoxetine or fluvoxamine altered MDMA-induced acute hyperthermia.




Biol Psychiatry. 2001 Sep 1;50(5):345-50.
Second-generation SSRIs: human monoamine transporter binding profile of escitalopram and R-fluoxetine.

Owens MJ, Knight DL, Nemeroff CB.

Laboratory of Neuropsychopharmacology, Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, 1639 Pierce Drive, Atlanta, GA 30322, USA.

BACKGROUND: Single isomers of the selective serotonin reuptake inhibitors citalopram (escitalopram, S-citalopram) and fluoxetine (R-fluoxetine) are currently under development for the treatment of depression and other psychiatric disorders. Previous studies conducted in laboratory animals have revealed that the biological effects on serotonin reuptake for citalopram reside in the S enantiomer. In contrast, both enantiomers of fluoxetine contribute to its biological activity. METHODS: In the present study, the potency and selectivity of escitalopram, R-fluoxetine, and all of the other currently available selective serotonin reuptake inhibitors were compared for binding affinity at the human serotonin, norepinephrine, and dopamine transporters and several select neurotransmitter receptors using radioligand binding assays. RESULTS: Both escitalopram and R-fluoxetine were potent inhibitors of the serotonin transporter (K(i) = 1.1 and 1.4 nmol/L, respectively). Escitalopram was the most serotonin transporter-selective compound tested and was approximately 30-fold more potent than R-citalopram. CONCLUSIONS: As noted previously, paroxetine and sertraline possess moderate affinity (<50 nmol/L) for the human norepinephrine transporter and dopamine transporter, respectively. R-Fluoxetine, unlike the other selective serotonin reuptake inhibitors, possesses moderate affinity (K(i) = 64 nmol/L) for the serotonin 2C receptor. Potential clinical correlates of these unique attributes of escitalopram and R-fluoxetine are discussed.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11543737&dopt=Abstract fluoxetine




Neuropharmacology. 2001 Sep;41(4):443-53.
Effects of norfluoxetine, the major metabolite of fluoxetine, on the cloned neuronal potassium channel Kv3.1.

Choi BH, Choi JS, Yoon SH, Rhie DJ, Min DS, Jo YH, Kim MS, Hahn SJ.

Department of Physiology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, South Korea.

The effects of fluoxetine and its major metabolite, norfluoxetine, were studied using the patch-clamp technique on the cloned neuronal rat K(+) channel Kv3.1, expressed in Chinese hamster ovary cells. In whole-cell recordings, fluoxetine and norfluoxetine inhibited Kv3.1 currents in a reversible concentration-dependent manner, with an IC(50) value and a Hill coefficient of 13.11+/-0.91 microM and 1.33+/-0.08 for fluoxetine and 0.80+/-0.06 microM and 1.65+/-0.08 for norfluoxetine at +40 mV, respectively. In inside-out patches, norfluoxetine applied to the cytoplasmic surface inhibited Kv3.1 with an IC(50) value of 0.19+/-0.01 microM. The inhibition of Kv3.1 currents by both drugs was characterized by an acceleration in the apparent rate of current decay, without modification of the activation time course and with relatively fewer effects on peak amplitude. The degree of inhibition of Kv3.1 by norfluoxetine was voltage-dependent. The inhibition increased steeply between 0 and +30 mV, which corresponded with the voltage range for channel opening. In the voltage range positive to +30 mV, inhibition displayed a weak voltage dependence, consistent with an electrical distance delta of 0.31+/-0.05. The association (k(+1)) and dissociation (k(-1)) rate constants for norfluoxetine-induced inhibition of Kv3.1 were 21.70+/-3.39 microM(-1) s(-1) and 14.68+/-3.94 s(-1), respectively. The theoretical K(D) value derived by k(-1)/k(+1) yielded 0.68 microM. Norfluoxetine did not affect the ion selectivity of Kv3.1. The reversal potential under control conditions was about -85 mV and was not affected by norfluoxetine. Norfluoxetine slowed the deactivation time co




Can J Clin Pharmacol. 2001 Fall;8(3):146-52.
Examining the Saskatchewan health drug database for antidepressant use: the case of fluoxetine.

Joffe RT, Iskedjian M, Einarson TR, O'Brien BJ, Stang MR.

Faculty of Health Sciences, McMaster University, Hamilton, Canada.

OBJECTIVE: To examine the use of fluoxetine in an adult population in Saskatchewan. METHODS: All adults in the Saskatchewan health care databases who had begun fluoxetine therapy between January 1992 and June 1996 and had not received an antidepressant in the six months before the index fluoxetine prescription were identified. Fluoxetine use for the subsequent six-month period was examined. The rates of completion of six months of fluoxetine, rates of stopping, switching to another serotonin-selective reuptake inhibitor (SSRI) or other class of antidepressant, resumption of fluoxetine, as well as average dosages taken and mean duration of therapy were determined. Rates were summarized as means with standard deviation. RESULTS: Data were obtained for 11,322 subjects, of whom 68.2% were women; 17.4% were 65 years of age or older. The average prescribed daily dose of fluoxetine was 22.5 mg (SD=21.7) and the average duration was 88.1 days (SD=57.2). Only 18.9% of patients filled prescriptions for six months, 7049 (62.3%) stopped fluoxetine at least once for one month or more, and 17.3% were titrated to a higher dose, on average 71 days (SD=44) after the initiation of fluoxetine. The proportion of patients switching to another antidepressant was 13.6% (3.3% to another SSRI, 10.3% to other classes), after a mean of 69 days (SD=51) of fluoxetine treatment. CONCLUSIONS: The authors' data suggest that there is a potential underutilization of fluoxetine in the study population. Further research may be warranted to determine the proportion of depressed patients in this population and to better understand the stop-switch-resume pattern of antidepressant use.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11574897&dopt=Abstract fluoxetine




J Chromatogr B Biomed Sci Appl. 2001 Sep 25;761(2):147-58.
High-performance liquid chromatographic method to screen and quantitate seven selective serotonin reuptake inhibitors in human serum.

Tournel G, Houdret N, Hedouin V, Deveau M, Gosset D, Lhermitte M.

Institut de Medecine Legale de Lille, Faculte de Medecine, Universite de Lille II, France.

A high-performance liquid chromatographic screening method (HPLC) is described for the determination of seven selective serotonin reuptake inhibitors (SSRIs) (fluvoxamine, milnacipran, paroxetine, sertraline, fluoxetine, citalopram, venlafaxine) and for three pharmacologically active N-demethylated metabolites (desmethylcitalopram, didesmethylcitalopram and norfluoxetine). A tricyclic antidepressant, clomipramine, was used as an internal standard. The method consists of liquid extraction of serum after alcalinisation at pH 9.50, followed by chromatography on a Beckman C18 reversed-phase column. Compounds were detected at 200.4 nm. The standard curves were linear over a working range of 50-1,000 ng/ml for fluvoxamine, 15-1,000 ng/ml for fluoxetine, 25-500 ng/ml for norfluoxetine, 50-500 ng/ml for sertraline, 20-500 ng/ml for paroxetine, 25-550 ng/ml for citalopram, 25-750 ng/ml for desmethylcitalopram, 25-800 ng/ml for didesmethylcitalopram, 25-650 ng/ml for milnacipran, and 25-500 ng/ml for venlafaxine. The quantitation limits of the method were 15 ng/ml for fluoxetine, 20 ng/ml for paroxetine, 25 ng/ml for venlafaxine, norfluoxetine and citalopram, and its metabolites, 40 ng/ml for sertraline and 50 ng/ml for fluvoxamine. No interferences were noted with this sensitive and specific method which can be used for therapeutic drug monitoring.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11587344&dopt=Abstract fluoxetine




Brain Res. 2001 Oct 12;915(2):218-26.
On the antinociceptive effect of fluoxetine, a selective serotonin reuptake inhibitor.

Singh VP, Jain NK, Kulkarni SK.

Pharmacology Division, University Institute of Pharmaceutical Sciences, Panjab University, 160 014, Chandigarh, India.

Antidepressant drugs are reported to be used as co-analgesics in clinical management of migraine and neuropathic pain. The mechanism through which they alleviate pain remains unknown. The present study explores the possible mechanism of a selective serotonin reuptake inhibitor (SSRI) fluoxetine-induced antinociception in animals. Acetic acid-induced writhing, hot plate and tail-flick test were used to assess fluoxetine-induced antinociception. Fluoxetine (5-20 mg kg(-1), i.p.) produced a significant and dose-dependent antinociceptive effect against acetic acid-induced writhing in mice. Fluoxetine (20 mg kg(-1)) also exhibited antinociceptive effect in tail flick as well as hot plate assays. Further, i.c.v. administration of fluoxetine showed significant antinociception against writhing test in rats. However, fluoxetine (1 microg/10 microl/rat, i.c.v.) did not exhibit any antinociceptive effect in serotonin-depleted animals. Further, pindolol (10 mg kg(-1), i.p.) enhanced fluoxetine-induced antinociceptive effect. The antinociceptive effect of fluoxetine was sensitive to blockade by naloxone (5 mg kg(-1), i.p.) and naltrexone (5 mg kg(-1), i.p.). These data suggest that fluoxetine-induced antinociception involves both central opioid and the serotoninergic pathways.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11595211&dopt=Abstract fluoxetine




Mol Psychiatry. 2001 Nov;6(6):610, 725-8.
Fluoxetine enhances cell proliferation and prevents apoptosis in dentate gyrus of maternally separated rats.

Lee HJ, Kim JW, Yim SV, Kim MJ, Kim SA, Kim YJ, Kim CJ, Chung JH.

Kohwang Medical Research Institute, College of Medicine, Kyung Hee University, 1 Hoegi-Dong, Tongdaemoon-Ku, Seoul, 130-701, Korea.

The mother-infant relationship is an instinctive phenomenon, and loss of maternal care in early life influences neonatal development, behavior and physiologic responses.(1,2) Furthermore, the early loss may affect the vulnerability of the infant to neuropsychiatric disorders, such as childhood anxiety disorders, personality disorders and depression, over its lifespan.(3,4) Fluoxetine is prescribed worldwide for depression and is often used in the treatment of childhood mental problems related to maternal separation or loss of maternal care.(5,6) In the present study, fluoxetine was administrated to rats with maternal separation to determine its effects on neuronal development, in particular with respect to cell proliferation and apoptosis in the dentate gyrus of the hippocampus. Rat pups were separated from their mothers and socially isolated on postnatal day 14 and were treated with fluoxetine (5 mg kg(-1)) and 5-bromo-2'-deoxyuridine (BrdU) (50 mg kg(-1)) for 7 days, after which immunohistochemistry and a terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining were carried out. In the pups with maternal separation treated with fluoxetine, the number of BrdU-positive cells was significantly increased and that of TUNEL-positive cells was significantly decreased in the dentate gyrus compared to pups with maternal separation that did not receive fluoxetine treatment. These findings indicate that fluoxetine affects new cell proliferation and apoptosis, and we propose that fluoxetine may be useful in the treatment of maternal separation-related diseases.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11673802&dopt=Abstract fluoxetine

unica.it

RATIONALE: Recent preclinical and clinical studies have shown that selective serotonin re-uptake inhibitors modulate neurosteroid synthesis in an opposite manner. OBJECTIVES: The action of long-term administration of fluoxetine was investigated on the peripheral and central concentrations of 3alpha,5alpha-tetrahydroprogesterone (3alpha,5alpha-TH PROG) and 3alpha,5alpha-tetrahydrodeoxycorticosterone (of 3alpha,5alpha-TH DOC), progesterone, and pregnenolone in rats. We also investigated the effect of chronic treatment with fluoxetine on the foot-shock stress-induced increase in the plasma and brain concentrations of these steroids. METHODS: Fluoxetine was administered acutely (20 mg/kg) or chronically (10 mg/kg, once daily for 15 days). Steroids were extracted from plasma and brain, separated and purified by means of high-performance liquid chromatography, and quantified by means of radioimmunoassay. RESULTS: A single dose of fluoxetine (20 mg/kg, i.p.) induced in 20 min significant increases in the cerebral cortical and plasma concentrations of 3alpha,5alpha-TH PROG (+96% and +13%, respectively), 3alpha,5alpha-TH DOC (+129 and +31%, respectively), progesterone (+111 and +58%, respectively), and pregnenolone (+151 and +59%, respectively). In addition, the plasma concentration of corticosterone was also significantly increased (+24%) after acute administration of fluoxetine. In contrast, long-term administration of fluoxetine reduced the basal concentrations of these various steroids (ranging from -22 to -43%), measured 48 h after the last drug injection, in both brain and plasma. A challenge injection of fluoxetine (20 mg




Br J Pharmacol. 2000 Dec;131(7):1294-302.
Involvement of 5-HT(3) receptors in the nucleus accumbens in the potentiation of cocaine-induced behaviours in the rat.

Herges S, Taylor DA.

Department of Pharmaceutical Biology and Pharmacology, Victorian College of Pharmacy, Monash University, 381 Royal Parade, Parkville 3052, Victoria, Australia.

1. The present study investigated the central effects of the selective serotonin reuptake inhibitor (SSRI) fluoxetine and the role of 5-hydroxytryptamine(3) (5-HT(3)) receptors in the core of the nucleus accumbens (NAc) on cocaine-induced behavioural changes in rats. 2. The 5-HT(3) receptor antagonist ondansetron (1 or 10 ng) was microinjected bilaterally into the core of the NAc 60 min prior to peripheral cocaine (15 mg kg(-1), i.p.) administration followed by the assessment of locomotor activity, rearing activity and head bobs. Both doses of ondansetron attenuated cocaine's stimulatory effect on behaviours. 3. Fluoxetine (0.05 or 5 microg) microinjected bilaterally into the core of the NAc 30 min before peripheral administration of cocaine produced dose-dependent biphasic effects on cocaine-induced behaviours. Intra-NAc administration of 0.05 microg fluoxetine resulted in a potentiation of cocaine-induced behaviours, while the higher dose of the SSRI (5 microg) attenuated the stimulant effect of cocaine on behaviours. 4. To investigate a possible involvement of 5-HT(3) receptors in fluoxetine's facilitatory action, ondansetron (10 ng) was microinjected 30 min prior to fluoxetine (0.05 microg), which resulted in a significant attenuation of the facilitatory effect of fluoxetine on cocaine-induced behaviours. 5. Thus, 5-HT(3) receptors in the core of the NAc appear to mediate stimulatory effects on cocaine-induced locomotor activity, rears and head bobs, whereas the attenuation of cocaine-induced behaviours by fluoxetine at the higher dose, suggests the involvement of a different 5-HT receptor subtype.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11090100&dopt=Abstract fluoxetine