BASIC NUTRITIONAL INVESTIGATION

Lack of Effects by Tricyclic Antidepressant andSerotonin Inhibitors on Anorexia in MCG 101Tumor-Bearing Mice With Eicosanoid-Related

CachexiaWenhua Wang, MD, Anna Danielsson, Elisabeth Svanberg, MD, PhD, and

Kent Lundholm, MD, PhDFrom the Surgical Metabolic Research Laboratory at the Lundberg Laboratory for Cancer

Research, Department of Surgery, Sahlgrenska University Hospital, Goteborg, Sweden

OBJECTIVES: Anorexia is a major clinical problem in large number of patients with advanced cancerdisease. Serotonergic mechanisms are assumed to play a role in the process of feeding behavior duringnormal and pathologic circumstances, which may also involve cancer anorexia according to previousexperimental and clinical studies.METHODS: In the present study, we evaluated the effect of the tricyclic antidepressants desipramine (7.5mg � kg�1 � d�1, intraperitoneal) and imipramine (2 to 5 mg · kg�1 · d�1, intraperitoneal) the serotoninsynthesis inhibitor para-chlorophenylalanine (300 mg · kg�1 · d�1, intraperitoneal), the serotonin receptor5-HT2C antagonist cyproheptadine (5 mg · kg�1 · d�1, intraperitoneal) and the selective serotonin re-uptake inhibitor citalopram (20 mg · kg�1 · d�1, intraperitoneal) on anorexia in MCG-101 tumor-bearingmice, a model with significant anorexia and cachexia sensitive to cyclooxygenase inhibition. Also, MCG101–bearing mice develop well-recognized alterations in brain tryptophan/serotonin metabolism asincreased Trp, 5-HPT, and 5-HIAA during tumor progression.RESULTS: Daily provision of desipramine, imipramine, para-chloropheylalanine, cyproheptadine, andcitalopram at doses that cause behavioral and metabolic alterations in normal mice did not alter foodintake or body weight in tumor-bearing and healthy control mice. Also, the treatments did not decreaseelevated plasma concentrations of interleukin-6 and prostaglandin E2 in the tumor-bearing mice.CONCLUSIONS: Thus, our results do not support previous observations that serotonin metabolism itself isa major factor behind anorexia in tumor-bearing animals in general. Rather, other mechanisms, such aseicosanoid and nitric oxide–dependent pathways, seem to be more important for induction of anorexiaalong tumor progression in the present model.Nutrition 2003;19:47–53. ©Elsevier Science Inc. 2003

KEY WORDS: anorexia, cachexia, tricyclic antidepressant

INTRODUCTION

Anorexia is a major clinical problem in a substantial proportion ofpatients with advanced cancer, but effective means to alleviate lossof appetite are lacking, perhaps due to a complicated and unclearpathogenesis of cancer anorexia. The control of food intake isconceptually mediated by a variety of mechanisms such as psy-chological, neuronal, and humoral alterations and gastrointestinal,metabolic, and nutrient factors. Modifications in one or several ofthese components may participate in the regulation that causesanorexia.

Serotonergic mechanisms have been reported to play a signif-icant role in the normal process of feeding behavior, which may berelevant for cancer anorexia according to experimental and clinicalstudies.1 Tryptophan, the precursor of the neurotransmitter sero-tonin, was reported to mediate the onset of satiety under normaland pathologic conditions.1 Accordingly, the levels of plasma-freetryptophan and 5-HIAA (a serotonin metabolite) in the centralnervous system (CNS) of tumor-bearing rats and of plasma-freetryptophan in human patients with cancer-induced anorexia werereported to be significantly increased.2–4 Further, increased sero-tonin:dopamine (DA) ratios in the ventromedial hypothalamusnuclei (VMH) were reported to relate to the development ofcancer-induced anorexia,5,6 but others were unable to demonstratea role of 5-HT in tumor-induced anorexia.7 Also, imbalancedplasma amino acid levels with relevance for amino acid uptakeinto the brain was demonstrated in animals and patients withcancer-related anorexia.8–10 However, blockade of serotonin3 re-ceptors failed to prevent weight loss and improve protein nutri-tional state in cancer patients.5 However, Laviano et al. demon-strated that peripheral injection of interleukin-1 is followed by asignificant rise in brain tryptophan concentrations, which second-arily increases brain serotonergic activity due to increased avail-ability of brain tryptophan.11 In addition, cyproheptadine (CY), aserotonin antagonist, was reported to counteract cancer anorexia to

This study was supported in part by grants from the Swedish CancerSociety (2014, 01PAA, 4261), the Swedish Research Council (08712,13159, 13268), Tore Nilson Foundation, Assar Gabrielsson Foundation(AB Volvo), Jubileumskliniken Foundation, IngaBritt & Arne LundbergResearch Foundation, Swedish and Go¨teborg Medical Societies, and theMedical Faculty, Go¨teborg University.

Correspondence to: Kent Lundholm, MD, PhD, Department of Surgery,Sahlgrenska University Hospital, SE 413 45 Go¨teborg, Sweden. E-mail:kent.lundholm@surgery.gu.se

Nutrition 19:47–53, 2003 0899-9007/03/$30.00©Elsevier Science Inc., 2003. Printed in the United States. All rights reserved. PII S0899-9007(02)00921-8

some extent in 256 Walker carcinoma-bearing rats, and clinicaldata demonstrated a weight-enhancing effect by CY.12 Thus, re-ported data provide support that cancer anorexia may be mediatedby serotonergic mechanisms, but additional transmittors such asneuropeptide Y, eicosanoides, and nitric oxide are certainly in-volved (unpublished results).13

Based on these studies, we evaluated the effects by systemicprovision of tricyclic antidepressants (TCAs) desipramine (DES)and imipramine (IMI), the serotonin synthesis inhibitor para-chlorophenylalanine (PCPA), the serotonin receptor 5-HT2C an-tagonist CY, and the selective serotonin reuptake inhibitor (SSRI)citalopram (CI) on anorexia in adult non-growing MCG-101tumor-bearing mice.

MATERIALS AND METHODS

Animals

Adult, female, age-matched C57BL/6 mice (20–25 g; B&K Uni-versal AB, Sollentuna, Sweden) were housed in groups of three tofive in plastic cages and received laboratory rodent chow (ALABAB, Stockholm, Sweden) and tap water ad libitum 14 d beforeexperimentation in a temperature-controlled room with a 12-hdark/light cycle, to provide stable experimental conditions includ-ing constant body weight before the start of the experiments. Theanimals were placed on a wire floor to adapt to the specificexperimental condition 3 d before the experiments. These facilitieswere necessary for appropriate measurements of food intake inmice.

This study was approved by the Animal Ethical Committee atthe Goteborg University.

Tumor Implantation and Animal Monitoring

Tumor-bearing mice were implanted subcutaneously and bilater-ally in the flanks with 3 to 5 mm3 of a transplantablemethylcholanthrene-induced sarcoma (MCG 101) on day 0 of thetumor experimental period. Food intake and body weight (includ-ing tumor) were registered daily between 8 and 9 AM after intra-peritoneal injections of 0.1 mL of various drugs. All tumor-bearinganimals were killed on day 10 after tumor implantation, whentumor-bearing mice are significantly anorectic and have profoundalterations in body composition, as described elsewhere.14 Plasmasamples were taken by cardiac puncture, and prostaglandin E2

(PGE2) and interleukin-6 (IL-6) determinations were performed asdescribed elsewhere.15,16

The MCG 101–bearing model represents adult non-growinganimals with constant body composition over time in healthynon–tumor-bearing mice. The growing MCG tumor drains thehost’s body fat and carcass for the synthesis of the expandingtumor compartment. Thus, loss of carcass dry tissue is more or less

quantitatively transferred to represent dry tumor tissue. The energyexpense for this translocation, in light of anorexia, is derived froma continuous decrease in whole-body energy turnover and a de-crease in physical activity. Thus, this model is particularly suitablefor quantitative aspects of anorexia and energy balance becausehost growth does not occur. Moreover, previous studies in ourlaboratory demonstrated that MCG 101–bearing mice displaywell-recognized metabolic alterations in brain 5-HT metabolismwith significantly increased tissue concentrations of tryptophanand 5-HIAA, whereas serotonin and 5-HTP (5-hydroxytryptophan)levels were borderline.17

Drug Provision and Animal Groups

The TCAs IMI and DES (Sigma Chemical Co., St. Louis, MO,USA) were dissolved in vehicle (0.9% NaCl containing 0.25%Tween 80) to produce concentrations of 0.625 and 0.417 mg/mL,respectively. The dosages of IMI and DES used in the presentstudy were chosen according to previous studies on appetite and5-HT metabolism.1 The duration of the entire experimental periodof IMI and DES treatment was 35 d with 10 animals in each group(Fig. 1). The period from day �25 to day 0 was a non–tumor-experimental period, and the period from day 0 to day 10 was thetumor-bearing period for the same groups of mice. IMI was givenat 2 mg · kg�1 · d�1 (low dose) from day �25 to day �19 and at5 mg · kg�1 · d�1 (high dose) from day �18 to day 10. DES (7.5mg · kg�1 · d�1) was given from day �11 to day 10.7

The serotonin synthesis inhibitor PCPA, the serotonin receptorof 5-HT2C antagonist CY, and the SSRI CI were kindly providedby Dr. Eriksson (Institute of Physiology and Pharmacology, Gote-borg University, Goteborg, Sweden). PCPA, CY, and CI weredissolved in saline to produce concentrations of 60, 1, and 4mg/mL, respectively. Dimethylsulfoxide was reported to be asuitable solvent in previous studies without side effects at lowconcentrations in animal experiments.18 Appropriate handling ofdrugs and dosages of PCPA, CY, and CI used in the present studywere recommended by the provider according to physiologic ex-periments in rats as used by others.7 In experiments with serotonininhibition, the non–tumor-bearing control period was 17 d, withsix mice in each group. Sham operation was performed on day 0.PCPA (300 mg · kg�1 · d�1) was given from day 6 to day 9; CY(5 mg · kg�1 · d�1) and CI (20 mg · kg�1 · d�1) were given intra-peritoneally from day 1 to day 9 in volumes of 0.1 mL. Consid-erably lower doses of CI (0.1–1 mg/kg) were reported to alter5-HTP and 5-HT concentrations in mouse brain with behavioraleffects19 and in the hypothalamus and hippocampus of mice.20

One milligram per kilogram of CY was used in mouse experi-ments21; comparable doses of PCPA (350–400 mg/kg) were usedin other studies.19,22

In the tumor-bearing groups, the duration of the entire treat-ment period with serotonin antagonists was 10 d, with 10 mice in

FIG. 1. Provision of DES and IMI according to the experimental design explained in MATERIAL AND METHODS. DES, desipramine; IMI, imipramine.

48 Wang et al. Nutrition Volume 19, Number 1, 2003

each group (Fig. 2). Injections of CI, CY, and PCPA were given asdescribed above.

Statistics

Results are presented as mean � standard error of the mean.Time-course changes of food intake and body weight across ani-mal groups were compared by two-way analysis of variance forrepeated measures. Statistics are presented for differences betweengroups, changes over time, and interactions between group andtime. P � 0.05 was considered statistically significant. Thechanges in PGE2 and IL-6 across groups was analyzed by one-wayanalysis of variance.

RESULTS

Food Intake and Body Weight in Non–Tumor-Bearing Miceon TCA and Serotonin Inhibitors

All animals in the TCA- and serotonin-treated groups had similarfood intakes and body weights at the beginning of the experiments,

and no significant difference was found during drug treatments(Figs. 3–6). Food intake and body weight were registered for 25and 17 d, respectively, in mice on TCA and 5-HT inhibitors. Therewas no significant effect by chronic DES or IMI provision (Figs.3 and 4). Food intake was rather constant, and body weightincreased only slightly before tumor implantation in all threegroups (Figs. 3 and 4). Also, PCPA, CY, and CI treatment had noeffect on the food intake and body weight of non–tumor-bearingmice (Figs. 5 and 6).

Food Intake, Body Weight, and Body Composition in Tumor-Bearing Mice on TCA and Serotonin Inhibitors

The effects of DES and IMI on food intake and body weight oftumor-bearing mice were subsequently evaluated in the sameanimals used before tumor implantation (Figs. 3 and 4). Theeffects of PCPA, CY, and CI on tumor-bearing mice were evalu-ated in separate and parallel groups of tumor-bearing and non–tumor-bearing mice (Fig. 7). Neither TCA nor serotonin inhibitorsimproved food intake or body weight in MCG-101 tumor-bearingmice during the 10-d tumor-bearing period as evaluated by anal-

FIG. 2. Provision of PCPA, CY, and CI according to the experimental design explained in MATERIAL AND METHODS. CI, citalopram; CY, cyproheptadine;PCPA, para-chlorophenylalanine.

FIG. 3. Time-course changes of food intake in DES, IMI, and CON mice including during non-tumor and tumor-bearing periods (n � 10 in each group).P � 0.05, between groups; P � 0.01, over time; P � 0.01, interaction of group and time. CON, sham treatment; DES, desipramine; IMI, imipramine.

Nutrition Volume 19, Number 1, 2003 49Neurotransmitters and Anorexia

ysis of variance for repeated measures. Analysis of tumor weightand body composition at day 10 showed no significant differenceby any of the drugs in the different animal groups (data notshown). This means that carcass weights (body weight minustumor weight) did not differ across groups.

Plasma PGE2 and IL-6 levels were compared among drug-treated tumor-bearing mice. CY-treated tumor-bearing mice hadsignificantly higher plasma PGE2 and IL-6 levels at the end of thetumor-bearing period, and CI-treated tumor-bearing mice had sig-nificantly increased plasma IL-6 levels (day 10; Fig. 8).

DISCUSSION

Control of food intake is probably a complicated physiologicprocess that integrates activation in the CNS and peripheral tis-

sues.23,24 During tumor growth, anorexia to some extent explainsthe development of malnutrition, which influences patients’ sur-vival. Cytokines such as IL-1�, IL-6, and tumor necrosis factor-�(TNF-�), regarded as anorexigenic cytokines, have been reportedto act on cells in the CNS and peripheral tissues in various clinicaland disease-related conditions. Proinflammatory cytokines there-fore have been suggested as major factors inducing cancer-relatedanorexia in a variety of tumor-bearing models, although the extentto which such effects act directly on the CNS or indirectly viaperipheral tissues is still unclear.25–27 Thus, IL-1� and TNF-� inanimals with induced systemic metabolic effects, such as anorexia,increased energy expenditure, and decreased lipoprotein lipaseactivity, produce effects similar to those seen in cancer cachex-ia.26,28 Increased IL-6 expression occurs in tumor-bearing mice,probably as a significant factor in the development of experimental

FIG. 4. Time-course changes of body weight (including the tumor) in DES, IMI, and CON mice during non-tumor and tumor-bearing periods (n � 10 ineach group). P � 0.05, between groups; P � 0.01, over time; P � 0.05, interaction of group and time. CON, sham treatment; DES, desipramine; IMI,imipramine.

FIG. 5. Time-course changes of food intake in PCPA, CY, CI, and CON non–tumor-bearing mice (n � 6 in each group). P � 0.05, between groups; P �0.01, over time; P � 0.01, interaction of group and time. CI, citalopram; CON, sham treatment; CY, cyproheptadine; PCPA, para-chlorophenylalanine.

50 Wang et al. Nutrition Volume 19, Number 1, 2003

cachexia, as supported by our recent experiments in knockoutmice.15,27 Accordingly, attenuation of proinflammatory cytokinesin the CNS or peripheral tissues of tumor-bearing mice wouldattenuate tumor-related anorexia. In support of this conclusion,systemic provision of anti–TNF-�, IL-1 receptor antagonists, orintra-VMH injections of an IL-1 receptor antagonist attenuated thedevelopment of anorexia and cachexia in tumor models simulta-neously with a decrease in host inflammatory response.29–32

Cytokines also may act in concert with other metabolic path-ways to induce anorexia. In this context, the immune system mayact as a sensory organ for non-cognitive stimuli such as growingtumors. Cytokines themselves also may be recognized by CNSmechanisms as a stressor.33 Thus, increased production and secre-tion of IL-1 may facilitate tryptophan supply to the brain, and IL-1itself may act on the VMH to increase its neuronal activity and5-HT release.11,34 Accordingly, megestrol acetate may downregu-late the synthesis and release of cytokines and thereby relieve thesymptoms of cancer anorexia by mechanisms that reduce theproduction of cytokines and serotonin.35 Accordingly, others re-ported upregulation of IL-1� mRNA in brain regions (cerebellum,

cortex, and hypothalamus).6 However, in recent experiments, wewere unable to demonstrate that CNS-produced IL-1�, IL-6, andTNF-� would play a direct role in cancer-induced anorexia intumor-bearing mice.13 Thus, we could not demonstrate increasedprotein levels of these cytokines in brain areas of known impor-tance for the control of appetite during the development of an-orexia based on immunohistochemical analyses, and our previousstudies indicated decreased overall concentrations of IL-6 mRNAin the brain of MCG 101–bearing mice.15 However, aside fromcytokine-dependent pathways, there may be other mechanisms ofimportance for the pathogenesis of cancer-related anorexia such asthe nitric oxide (NO) system and systemic or local production ofeicosanoids based on the finding that NO synthase (NOS) andcyclooxygenase inhibitors decreased tumor growth and improvedanorexia in tumor-bearing animals.16,26,36 In addition, experimentson normal mice with provision of PGE2 caused anorexia, butevidence that NO and PGE2 should act directly on cells in CNS islacking. Despite this lack of evidence, we presently favor thehypothesis that the development of anorexia in some tumor modelsis in part eicosanoid dependent, in accordance with high concen-

FIG. 6. Time-course changes of body weight in PCPA, CY, CI, and CON non–tumor-bearing mice (n � 6 in each group). P � 0.05, between groups; P� 0.01, over time; P � 0.01, interaction of group and time. CI, citalopram; CON, sham treatment; CY, cyproheptadrine; PCPA, para-chlorophenylalanine.

FIG. 7. Time-course changes of food intake and body weight in tumor-bearing mice treated with PCPA, CY, CI, and CON injection (n � 10 in each group).Food intake: P � 0.05, between groups; P � 0.01, over time; P � 0.01, interaction between time and group. Body weight: P � 0.05, between groups; P� 0.01, over time; P � 0.01, interaction between time and group. CI, citalopram; CON, sham; CY, cyproheptadrine; PCPA, para-chlorophenylalanine.

Nutrition Volume 19, Number 1, 2003 51Neurotransmitters and Anorexia

tration of plasma PGE2 in all current groups of tumor-bearing mice(Fig. 8), compared with non–tumor-bearing mice.16 We accord-ingly reported that indomethacin treatment partly improved appe-tite in mice, rats, and undernourished patients with metastatic solidtumors.16,36,37 However, such effects are not a unanimous findingin tumor-bearing models.38 NO mechanism also may involvetumor growth and thereby secondarily influence appetite becauseadministration of NOS inhibitors attenuated both tumor growthand improved anorexia in mice.36 The possibility of a role of NOin CNS for anorexia is thus an interesting and new perspective. Ina recent study on tumor-bearing mice, we found inducible NOSexpression to be downregulated concomitantly with an increasedc-fos expression in nuclei of importance for control of food intake,whereas neuronal and endothelial NOS were upregulated in thesame nuclei of mice with other nutritional aberrations (unpub-lished observations). Thus, it remains to be determined how NOalterations relate to the control of appetite in tumor-bearing ani-mals, perhaps in relation to serotonin metabolism as described forobese Zucker rats.39

Physiologically, brain tryptophan and serotonin were reportedto play a pivotal role in the regulation of feeding behavior.1

Increased brain serotonin activity usually is associated with reduc-tion of food intake.40,41 Accordingly, increased availability oftryptophan to the brain and subsequently increased serotonin ac-tivity may represent a pathogenic mechanism for cancer-relatedanorexia as proposed for the control of normal satiety.2,42,43 Evi-dence indicates that increased plasma tryptophan levels lead toincreased concentration of tryptophan in cerebrospinal fluid andincreased VMH serotonin synthesis, which would mediate thedevelopment of anorexia in tumor-bearing rats and patients.11,34 Inaddition, the relation between concentrations of DA and serotonin,limited to the lateral hypothalamic area and VMH, was related tocancer anorexia.44 Thus, oral administration of neutral aminoacids, which compete with tryptophan for brain entry, may reducebrain tryptophan availability, restore brain serotonin activity tonormal levels, and thereby cause a significant improvement ofcancer anorexia.45 Similarly, intraventricular injections of PCPAdelayed the development of anorexia by modulation of brainserotonin activity in a rat tumor model,46 although the same studyfailed to demonstrate a direct relation between brain serotoninconcentration and appetite in tumor-bearing or control rats.Chronic systemic administration of DES and IMI attenuatedliposaccharide-induced depressive behavioral symptoms in rats,including anorexia and loss of body weight, whereas provision ofSSRIs and the dual-acting serotonin/noradrenaline reuptake inhib-itors did not show this effect.47,48 Inhibition of proinflammatory

cytokines or promotion of production of anti-inflammatory cyto-kines as IL-10 were suggested as alternative mechanisms47,48

because incubation of activated monocytes with TCA was reportedto inhibit the release of proinflammatory cytokines in vitro.49

However, in our present study, chronic systemic administration ofDES and IMI did not cause significant changes in food intake orbody weight in tumor-bearing or healthy control mice. Also, DESor IMI treatment had no effect on elevated plasma concentrationsof IL-6 or PGE2 in the tumor-bearing mice.

Serotonin inhibitors share the monoamine inhibitory propertiesof TCA, but largely lack their immunosuppressive effects, e.g., CI,which is an agent of SSRI.49–51 PCPA treatment reduced serotoninconcentrations in the hypothalamus and intestinal tissue.46,52 Pos-sible effects of PCPA on food intake thus may be mediated byreduction of serotonin concentrations in the CNS or peripheraltissues, although there was no correlation between intestinal sero-tonin concentrations and food intake in normal rats.53,54 Recently,CI was reported to reduce food intake in a dose-dependent fashionaccompanied by increased extracellular concentrations of seroto-nin in the forebrain of rats.55 Thus, presynaptic 5-HT1A receptorsmay be involved in the mechanism of food intake in normal rats.56

CY, a known antagonist to the serotonin receptor 5-HT2C, alsomay stimulate appetite in physiopathologic conditions, although itseffect on cancer-induced anorexia is still controversial.57 Theselective 5-HT2C antagonist, RS-102221, increased food intakeand body weight when injected intraperitoneally into normal rats,and 5-HT2C receptor knockout mice were reported to be hy-perphagic.58,59 In contrast to such observation, our present exper-iments, with provision of PCPA, CY and CI, did not show anysignificant improvements of food intake and body weight in tumor-bearing mice, had no adverse effects in normal mice, and showedno attenuation of plasma concentrations of IL-6 and PGE2 intumor-bearing mice. This lack of evidence for TCA, PCPA, CY,and CI in the control of tumor-related anorexia in the currentmodel is not explained by insufficient drug concentrations, becausethe drugs were provided in doses corresponding to those used inphysiologic experiment on rats with observed effects47,48 (Dr.Eriksson personal communication) or at doses higher than thoseused in comparable physiologic studies on mice.20 Actually, CYand CI increased plasma IL-6 and to some extent plasma PGE2, aphenomenon that demonstrates that the drug intervention causedsystemic effects. However, it is not possible to judge the extent towhich increased plasma PGE2 and IL-6 levels might counteract apositive role of serotonin inhibitors, although several inhibitorshad no observed effects on IL-6 and PGE2. Our previous experi-ments on gene knockout mice demonstrated a link between IL-6and cachexia in this model including PGE2. Non-specificcyclooxygenase-inhibition clearly attenuated anorexia in MCG-bearing mice, but it is still unclear to what extent this represents adirect effect on CNS or an indirect effect via the tumor andperipheral tissue metabolism.26

In conclusion, daily provision of TCA, PCPA, CY, and CI didnot improve food intake and body weight and did not decreaseplasma concentrations of IL-6 and PGE2 in MCG 101 tumor-bearing mice that became anorectic during tumor growth. Thesenegative results should be compared with pronounced effects onappetite by physiologic cyclooxygenase and NO inhibition in thismodel.36 Thus, our results do not support previous observations ofa direct relation between serotonin metabolism and tumor-inducedanorexia as a general phenomenon. Other mechanisms such aseicosanoid and NO-dependent pathways are more likely for theinduction of anorexia along tumor progression in this model.

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FIG. 8. Plasma levels of PGE2 and IL-6 in MCG 101 tumor-bearing micefrom groups treated with DES, IMI, PCPA, CY, and CI in relation toCON-injected MCG 101 tumor-bearing mice (n � 5 in each group). 100%of PGE2 � 948 pg/mL, 100% of IL-6 � 697 pg/mL. *P � 0.05 versuscontrols. CI, citalopram; CON, sham; CY, cyproheptadrine; DES, desipra-mine; IL-6, interleukin-6; IMI, imipramine; PGE2, prostaglandin E2;PCPA, para-chlorophenylalanine.

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Nutrition Volume 19, Number 1, 2003 53Neurotransmitters and Anorexia