Prozac
Contrasting Fos expression induced by acute reboxetine and fluoxetine in the rat forebrain: neuroanatomical substrates for the antidepressant effect.

Miyata S, Hamamura T, Lee Y, Miki M, Habara T, Oka T, Endo S, Taoka H, Kuroda S.

Department of Neuropsychiatry, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikata-cho, 700-8558, Okayama, Japan.

RATIONALE. Antidepressants preferentially facilitating serotonin seem to be particularly effective for treating the anxiety and aggressive component of the depressive syndrome, whereas those with a noradrenergic profile seem to be more effective in reducing psychomotor retardation, although their overall antidepressant effects are about the same. However, the mechanism of this difference remains unknown. OBJECTIVES. To investigate the neural substrate for the different therapeutic efficacies of fluoxetine and reboxetine, we examined the regional Fos immunoreactivity (Fos-ir) induced by the two agents. METHODS. Male Wistar rats (290-330 g) were given a subcutaneous injection of fluoxetine (5 or 10 mg/kg), reboxetine (5 or 10 mg/kg) or saline. Two hours later, rats were perfused through the ascending aorta and their brains were processed for Fos immunohistochemistry. Fos-ir was quantified by counting the number of Fos-ir-positive nuclei in six areas of the forebrain. RESULTS. The shell of the nucleus accumbens was the only region in which both fluoxetine and reboxetine equally increased Fos-ir expression. Fluoxetine particularly induced Fos-ir in the central nucleus of the amygdala. In contrast, reboxetine induced Fos-ir in the cingulate cortex area 3 and the lateral orbital cortex. CONCLUSIONS. These results suggest that the shell region may be one possible target for the antidepressant effects of fluoxetine and reboxetine. Furthermore, the difference in their clinical effects may depend on their different target sites of action.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15551066&dopt=Abstract fluoxetine Prozac



Prozac
Ratio of plasma fluoxetine to norfluoxetine concentrations and associated sedation.

Keck PE Jr, McElroy SL.

Biological Psychiatry Program, University of Cincinnati College of Medicine, University of Cincinnati Hospital, OH 45267-0559.

BACKGROUND: Sedation is an often unanticipated but clinically significant side effect in some patients treated with fluoxetine. To date, no clinical or pharmacokinetic factors have been identified in association with sedation in fluoxetine-treated patients. We hypothesized that patients experiencing sedation might have elevated plasma concentrations of fluoxetine and/or norfluoxetine compared with patients without sedation. METHOD: Plasma samples from eight patients reporting new-onset sedation following initiation of treatment with fluoxetine and from 14 consecutive patients also receiving fluoxetine but who experienced no sedation were analyzed for fluoxetine and norfluoxetine concentrations. RESULTS: Patients in the two groups did not differ significantly in age, sex distribution, diagnoses, mean dose or duration of fluoxetine treatment, or mean combined plasma concentrations of fluoxetine and norfluoxetine. However, the plasma ratio of fluoxetine to norfluoxetine was less than 1.0 in all patients reporting sedation and greater than 1.0 in all patients without sedation. Also, there was a significant difference between the mean +/- SD ratio of fluoxetine-to-norfluoxetine plasma concentrations in the group reporting sedation (0.6 +/- 0.1) and the group without sedation (1.7 +/- 0.8). CONCLUSION: The results of this study suggest an association between sedation and increased plasma concentrations of norfluoxetine compared with fluoxetine. Individuals reporting sedation may metabolize the parent drug differently than patients who do not experience sedation, leading to a relative increase in the proportion of the active metabolite, norfluoxetine.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1564047&dopt=Abstract fluoxetine Prozac



Prozac
Fluoxetine pretreatment potentiates intracisternal TRH analogue-stimulated gastric acid secretion in rats.

Shockley RA, LePard KJ, Stephens RL Jr.

Department of Physiology, Ohio State University, Columbus 43210.

Central injection of TRH or its metabolically stable analogue RX 77368 has been demonstrated to produce a vagal-dependent stimulation in gastric acid secretion. Accumulating evidence exists regarding the interaction of serotonin (5HT) with TRH containing neuronal systems. This study was performed to assess the effect of pretreatment with the 5HT uptake inhibitor fluoxetine on the TRH analogue-induced gastric acid secretory response. Systemic fluoxetine (30 mumol/kg, i.v.) produced a 43-85% increase in the intracisternal RX 77368 (78-780 pmol)-induced gastric acid output, while not affecting the basal acid response. The acid response to a lower dose of RX 77368 (26 pmol) was not altered. In addition, intracisternal fluoxetine (180 nmol) produced a 71% augmentation of the acid secretory response of i.c. RX 77368 (260 pmol). Intracisternal injection of lower doses (60, 120 nmol), or intravenous injection of 180 nmol of fluoxetine was ineffective in altering the intracisternal RX 77368-induced acid response. Pretreatment with the noradrenergic or dopaminergic uptake inhibitor desipramine or GBR 12909 did not alter the RX 77368-stimulated gastric acid secretory response. The results show that fluoxetine pretreatment potentiates the effect of intracisternal RX 77368 on acid secretion. The effect appears to be impulse dependent, and central sites of action are involved. The data suggest an interaction of synaptic serotonin with a RX 77368-elicited event (activation of TRH receptors, second messenger systems and/or firing of the motor vagus) results in potentiation of the RX 77368-induced gastric response.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1574606&dopt=Abstract fluoxetine Prozac



Prozac
Nelumbinis Semen reverses a decrease in 5-HT1A receptor binding induced by chronic mild stress, a depression-like symptom.

Jang CG, Kang M, Cho JH, Lee SB, Kim H, Park S, Lee J, Park SK, Hong M, Shin MK, Shim IS, Bae H.

Department of Pharmacology, College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Korea.

Depression is associated with a dysfunctional serotonin (5-hydroxytryptamine; 5-HT) system. More recently, several lines of evidence suggest that an important factor in the development of depression may be a deficit in the function and expression of 5-HT1A receptors. The present study assessed if Nelumbinis Semen (N.s.) had an anti-depression effect through reversing a decrease in 5-HT1A receptor binding in rats with depression-like symptoms induced by chronic mild stress. Using a 5-HT1A receptor binding assay, with a specific 5-HT1A receptor agonist, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino) tetralin), the mechanism of the anti-depression effect of N.s. on rats was investigated, and the effects compared with two well-known antidepressants, Hyperium Perforatum (St. Johns Wort) and fluoxetine (Prozac). Animals were divided into five groups: the normal (N) group without chronic mild stress (CMS), the control (C) group under CMS for 8 weeks, the Nelumbinis Semen (N.s.) treatment group under CMS for 8 weeks, the Hyperium Perforatum (H.p.) treatment group under CMS for 8 weeks and finally, the fluoxetine (F) treatment group under CMS for 8 weeks. Each treatment was administered to rats during the last 4 weeks of the 8-week CMS. A sucrose intake test was performed to test the anti-depression effect of N.s. The N.s. treatment significantly reversed the decreased sucrose intake under CMS (P < 0.05 compared to control group under CMS). In the CA2 and CA3 regions of the hippocampus, both N.s. and H.p. reversed the CMS-induced decrease in 5-HT1A receptor binding. In the I to II regions of the frontal cortex, N.s. and H.p. also reversed the CMS-induced decrease in 5-HT1A receptor binding, and even showed a significant increase in 5-HT1A receptor binding compared to the F treatment group (N.s. vs. P, p < 0.05, H.p. vs. P, p < 0.05). However, in the hypothalamus, all treatments reversed the CMS-induced decrease in 5-HT1A receptor binding. This reversal effect of N.s. on the decrease in 5-HT1A receptor binding in the frontal cortex, hippocampus and hypothalamus of rat brains was very similar to that of H.p, but different from that of F. It is concluded that N.s. presents an anti-depression effect through enhancing 5-HT1A receptor binding.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15554266&dopt=Abstract fluoxetine Prozac



Prozac
Fluoxetine shortens circadian period for wheel running activity in mice.

Possidente B, Lumia AR, McEldowney S, Rapp M.

Biopsychology Program, Skidmore College, Saratoga Springs, NY 12866.

Fluoxetine is a potent and specific serotonin re-uptake inhibitor and an effective antidepressant drug. Male mice were treated with either fluoxetine (8 mg/kg body weight per day) or saline. Wheel running activity was monitored for 2 weeks in a 12:12 LD cycle followed by 2 weeks in constant darkness (DD). Fluoxetine significantly shortened free-running circadian period for wheel running activity (23.93 +/- 0.08 h for fluoxetine treated mice versus 24.17 +/- 0.07 h for saline treated mice; p less than 0.03). These results are consistent with a role for serotonin in the regulation of circadian period in mice.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1617446&dopt=Abstract fluoxetine Prozac



Prozac
Stimulation of malignant growth in rodents by antidepressant drugs at clinically relevant doses.

Brandes LJ, Arron RJ, Bogdanovic RP, Tong J, Zaborniak CL, Hogg GR, Warrington RC, Fang W, LaBella FS.

Department of Medicine, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.

Tricyclic antidepressants, such as amitriptyline (Elavil), and the nontricyclic agent, fluoxetine (Prozac), bind to growth-regulatory intracellular histamine receptors, associated with anti-estrogen binding sites in microsomes and nuclei. The prototype anti-estrogen binding site/intracellular histamine receptor ligand, N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine HCl, inhibits normal cell proliferation in vitro but stimulates tumor growth in vivo. Because of their structural similarity to N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine HCl, we carried out studies to determine whether amitriptyline and fluoxetine stimulate tumor growth and/or development in rodents at concentrations relevant to the treatment of human depression (equivalent human dose range, approximately 100-150 mg/day for amitriptyline and approximately 20-80 mg/day for fluoxetine). All experiments were performed blinded. In studies of growth stimulation of transplantable syngeneic tumors, groups of mice were inoculated s.c. with C-3 fibrosarcoma cells or given i.v. or s.c. injections of B16f10 melanoma cells, followed 24 h later by daily i.p. injections of saline, amitriptyline, or fluoxetine. Tumor latency (fibrosarcoma), aggregate tumor weight (s.c. injected melanoma), or time to death from pulmonary metastasis (i.v. injected melanoma) was determined; drug-induced stimulation of DNA synthesis in C-3 fibrosarcoma cells in vitro was correlated with tumor growth acceleration in vivo. In a mammary carcinogenesis model, the effects of chronic saline, amitriptyline, or fluoxetine administration on the rate and frequency of development of mammary tumors in rats fed dimethylbenzanthracene (DMBA) were compared. Eight of 20 amitriptyline- or fluoxetine-treated mice developed fibrosarcoma tumors by day 5, as compared to none of 20 saline controls (P less than 0.002). Similarly, 20 of 21 DMBA-treated rats receiving the antidepressant drugs developed 33 mammary tumors by week 15 as compared to 5 tumors in 4 of 7 DMBA-treated rats receiving saline (P less than 0.001). For both models, tumor latency decreased 30-40% and, in the DMBA model, tumor frequency increased greater than 2-fold in the antidepressant-treated rats as compared to controls. Stimulation of fibrosarcoma growth in vivo correlated with a corresponding bell-shaped drug-induced increase in DNA synthesis in vitro. While the median time to death from pulmonary metastases did not differ among groups given i.v. injections of melanoma cells, a significant (P less than 0.01) stimulation of growth of s.c. injected melanoma was observed in mice receiving the antidepressants.(ABSTRACT TRUNCATED AT 400 WORDS)

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1617649&dopt=Abstract fluoxetine Prozac



Prozac
Fluoxetine blocks cloned neuronal A-type K+ channels Kv1.4.

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

Department of Physiology, Medical Research Center, College of Medicine, The Catholic University of Korea, Socho-gu, Seoul.

The effects of fluoxetine were studied on cloned K+ channel Kv1.4 stably expressed in Chinese hamster ovary (CHO) cells using the whole-cell configuration of the patch-clamp technique. Extracellular application of various concentrations of fluoxetine inhibited the amplitude of the peak current of Kv1.4 and accelerated its inactivation time course in a concentration-dependent manner. Thus, fluoxetine decreased Kv1.4 (the integral of the outward current) in a concentration-dependent manner; the IC50 was 33.1 +/- 2.5 microM. The inhibitory effect of fluoxetine was time-dependent. The apparent association (k) and dissociation (l) rate constants measured at +40 mV were 3.5 +/- 0.7 microM-1s-1 and 132.5 +/- 13.3 s-1, respectively. The Kd (= l/k) was 37.9 microM, which was close to the value obtained from the concentration-response curve. The block produced by fluoxetine increased steeply between -30 and 0 mV, which corresponded with the voltage range for channel opening. The fluoxetine block was constant at more depolarized potentials, suggesting that the block by fluoxetine was not voltage dependent. Our data indicate that fluoxetine blocks Kv1.4 channels by preferentially binding to open state.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14663209&dopt=Abstract fluoxetine Prozac



Prozac
Lack of association between fluoxetine and suicidality in bulimia nervosa.

Wheadon DE, Rampey AH Jr, Thompson VL, Potvin JH, Masica DN, Beasley CM Jr.

Division of Clinical Neurosciences, Eli Lilly and Company, Indianapolis, Ind 46285.

BACKGROUND: The coincidence of major depressive disorder in bulimia nervosa ranges from 35% to 80%. Because of this comorbidity and because suicidality (suicidal acts and ideation) is an inherent part of depression, assessment of the risk of suicide in patients with bulimia nervosa is of considerable interest. METHOD: Data from United States Investigational New Drug double-blind, placebo-controlled fluoxetine clinical trials in bulimia nervosa were analyzed comprehensively to assess the potential association between fluoxetine treatment and suicidality in 785 patients with DSM-III-R bulimia nervosa. Patients were predominantly women (98%), aged 17 to 63 years; of the randomly assigned patients, 16.9% exhibited 17-item Hamilton Rating Scale for Depression (HAM-D) total scores of 17 or greater at baseline (range, 0-31). Incidence of suicidality was analyzed by the incidence difference method. RESULTS: No fatal suicidal acts occurred; 9 (1.15%) of 785 patients made nonfatal attempts; 24 (3.06%) experienced emergent (text-defined) suicidal ideation. No statistically significant increases in the incidence of suicidal acts or suicidal ideation were observed among fluoxetine-treated compared with placebo-treated patients. A smaller percentage of fluoxetine-treated (2.0%) than placebo-treated (3.8%) patients experienced emergence of substantial suicidal ideation (change in baseline HAM-D Item 3 [suicide item] score of 0 or 1 to 3 or 4 during therapy). A statistically significantly greater proportion of fluoxetine-treated than placebo-treated patients experienced improvement in suicidal ideation (decrease in HAM-D Item 3 score) from baseline to endpoint (p = .026). CONCLUSION: Analyses of the incidence of suicidal acts and suicidal ideation did not indicate an increased risk of suicidality in patients with bulimia nervosa treated with fluoxetine compared with those treated with placebo.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1639742&dopt=Abstract fluoxetine Prozac