Visceral fat is associated with lower executive functioning in adolescents.

BACKGROUND: Obesity, a major risk factor for cardiometabolic disease, is associated with lower cognitive performance from childhood to senescence, especially on tasks of executive function. In the cardiovascular domain, fat stored viscerally rather than elsewhere in the body carries particularly high risk. It is unknown whether this is also true in case of obesity-cognition relationships. The aim of this study was to assess the cross-sectional relationship between visceral fat (VF) and cognitive performance in a community sample of healthy adolescents. METHODS: In a community-based sample of 983 adolescents (12-18 years old, 480 males), VF was quantified using magnetic resonance imaging, total body fat was measured using a multifrequency bioimpedance, and cognitive performance was assessed using a battery of cognitive tests measuring executive function and memory. RESULTS: We found that larger volumes of VF were associated with lower performance on six measures of executive function (P=0.0001-0.02). We also found that the association of VF with executive function was moderated by sex for a subset of measures, such that relationship was present mainly in female subjects and not in male subjects (sex-by-VF interaction: P=0.001-0.04). These relationships were independent of the quantity of total body fat and a number of potential confounders, including age, puberty stage and household income. CONCLUSIONS: Our results suggest that the adverse association between obesity and executive function may be attributed to fat stored viscerally and not to fat stored elsewhere in the body. They also suggest that female subjects compared with male subjects may be more sensitive to the potentially detrimental effects of VF on cognition.

Evolutionary pattern of human immunodeficiency virus (HIV) replication and distribution in lymph nodes following primary infection: implications for antiviral therapy.

Evolutionary patterns of virus replication and distribution in lymphoid tissue during the early phases of HIV infection have not been delineated. Lymph node (LN) biopsies were excised from patients at different times after the estimated time of primary infection. Within 3 months of the acute viral syndrome, HIV was mostly present in individual virus-expressing cells in LNs; trapping of virions in the follicular dendritic cell (FDC) network was minimal or absent, but was the predominant form of HIV detected in LNs of subjects with chronic infection, either recent (4-20 months after primary infection) or long-term (>2-3 years after primary infection). Plasma viremia was significantly higher in patients during the first 3 months than in those recently infected; however, there were no significant differences in the number of virus-expressing cells per square millimeter of LN tissue in these two groups. Numbers of virus-expressing cells in lymphoid tissue were significantly lower in the subjects with long-term infection than in the other two groups. Therefore, during the transition from primary to chronic HIV infection, the level of HIV replication in lymphoid tissue remains elevated despite the fact that viremia is significantly downregulated. These findings have implications for therapeutic strategies in primary HIV infection and in recent seroconvertors.

Induction of neonatal tolerance to H-2k in B6 mice does not allow the emergence of T cells specific for H-2k plus vaccinia virus.

Thymocytes and spleen cells from C57BL/6 mice (H-2b) neonatally tolerized to H-2k alloantigens do not generate an anti-vaccinia response restricted to H-2Kk when adoptively transferred to appropriate irradiated hosts. This is in sharp contrast to the case for negatively selected C57BL/6 spleen cells acutely depleted of alloreactivity. No evidence for suppression was found in cell mixture experiments. We have shown elsewhere that our neonatally tolerized animals have a centrally induced delection-type tolerance in the absence of obvious suppression.2 We now suggest that in the neonatally tolerized mouse, chronic, central delection of anti-H-2k clones during early T cell ontogeny eliminates the major source of cells able to give rise, via somatic mutation and expansion, to anti-H-2Kk + vaccinia specific cytotoxic T lymphocyte precursors (CTL-P) in the adult. A similar mechanism may operate in the (k + b) leads to b chimera; however, the presence of H-2kxb accessory and presenting cells may permit the eventual generation (via cross-stimulation) of an H-2k-restricted vaccinia-specific repertoire. This would account for our observation of such "aberrant recognition" CTL-P emerging in the spleens of older (k x b) leads to b chimeras.

Differences in the antibody response to human immunodeficiency virus-1 envelope glycoprotein (gp160) in infected laboratory workers and vaccinees.

Studies of the immune response to the human immunodeficiency virus (HIV) have been hampered by the antigenic diversity of the HIV envelope protein. In an effort to predict the efficacy of vaccination we have compared the systemic anti-envelope antibody response in seronegative volunteers immunized with recombinant gp160 (either in vaccinia or as soluble protein produced in baculovirus) derived from the HTLV-IIIB strain of HIV-1 and in two laboratory workers accidentally infected with the same strain. 11 of 14 vaccinees responded to immunization by producing anti-gp160 of similar titer and the same isotype as that seen in the laboratory workers. Four vaccinees also had antibody to the principal neutralizing domain (V3 loop) that was comparable in titer with that seen in the laboratory workers, but the fine specificity of anti-V3 antibody was qualitatively different in the two groups. Antibody that can block the interaction between CD4 and gp120 was present at comparable levels in three vaccines and the lab workers. Neutralizing antibody titers were markedly lower in the vaccinees than in the laboratory workers. In seven of the vaccinees, an immunodominant epitope was at amino acid 720-740. Analyses of monoclonal antibodies to this region indicate that they do not neutralize, bind to infected cells, nor function as immunotoxins. Although the anti-gp160 antibody response was of similar magnitude in both infected and vaccinated individuals, there were important qualitative differences.

V3-specific neutralizing antibodies in sera from HIV-1 gp160-immunized volunteers block virus fusion and act synergistically with human monoclonal antibody to the conformation-dependent CD4 binding site of gp120. NIH-NIAID AIDS Vaccine Clinical Trials Network.

Sera from 11 volunteers immunized with a recombinant HIV-1 gp160-expressing vaccinia virus (HIVAC-1e; Oncogen/Bristol-Myers Squibb, Seattle, WA) and boosted with baculovirus-derived rgp160 (VaxSyn; MicroGeneSys, Inc., Meriden, CT) were evaluated for functional serum antibodies and their epitopes. Sera obtained prior to boosting had undetectable HIV-1-specific IgG and neutralizing activity, and did not block HIV-1 from binding or fusing to CD4+ MT-2 cells. 14 d after boosting, sera from each volunteer contained HIV-1-specific IgG titers of 1:40 to 1:1,280. Five of these sera also contained neutralizing antibodies, where most or all neutralizing activity was blocked by a synthetic peptide corresponding to amino acids 307-330 of the V3 loop of gp120, indicating that neutralizing antibodies were mostly V3 loop-specific. All sera obtained after boosting contained HIV-1 binding/fusion-inhibition antibodies, and a significant portion of their activity was blocked by the V3 loop peptide, a result consistent with the presence of antibodies against the region of the V3 loop that participates in fusion. Three sera with V3 loop-specific neutralizing and fusion-inhibition antibodies were studied further. In competitive antibody binding experiments, antibodies reactive with the conformation-dependent, CD4 binding site of gp120 were undetectable in each serum. When evaluated in combination with a monoclonal antibody to the CD4 binding site of gp120, two sera demonstrated synergism in neutralizing assays, and all three sera demonstrated synergism in binding/fusion-inhibition assays, further indicating that the functional antibodies were primarily V3 loop-specific. The synergism also suggests that a vaccine that elicits strong serum antibody responses to both regions of gp120 may improve the potential for inducing protective immunity.

N-acetyl-cysteine and L-2-oxothiazolidine-4-carboxylic acid enhance contact-dependent growth of HIV in resting peripheral blood mononuclear cells (PBMC) in vitro and increase recovery of HIV from human-PBMC SCID mice.

OBJECTIVES: To ascertain the effects of N-acetyl-cysteine (NAC) and L-2-oxothiazolidine-4-carboxylic acid (OTC) on HIV replication in resting T lymphocytes mixed with chronically infected U1 promonocytic cells; examine the phenotypes of NAC- and OTC-treated cells; and monitor HIV recovery from hu-PBMC SCID mice (SCID mice infected with HIV-1BaL reconstituted with human peripheral blood mononuclear cells) treated with oral OTC. DESIGN AND METHODS: Unstimulated PBMC from uninfected donors preincubated for 2 days with pH-adjusted NAC or OTC were cultured at a concentration of 1 x 10(6) cells/ml with 100 U1 cells that were chronically infected with HIV-1IIIB. HI-1 production in the presence or absence of zidovudine was measured by p24 assay at 1-3 weeks, and results were compared with values from the same cell cultures maintained without NAC or OTC exposure. In some experiments U1 cells were separated from PBMC by a 0.4 micron membrane. NAC-treated and -untreated cells were subjected to FACS analysis of multiple-cell-surface adhesion and activation molecules and the results were compared. Hu-PBMC SCID mice were fed OTC for 3 days prior to infection with HIV-1BaL and for the next 3 weeks. Mice were then sacrificed and peritoneal lavage cells were cultured for virus analysis. RESULTS: Unstimulated, non-dividing PBMC supported high levels of HIV replication when in direct contact with U1 cells in the presence of NAC or OTC; CD2 and CD54 (I-CAM1) were down-regulated on NAC-treated PBMC; and OTC-treated mice produced significantly higher yields of HIV-1 from peritoneal cells than did untreated mice. CONCLUSIONS: At concentrations < or = 5 mM, NAC and OTC potentiate HIV growth in unstimulated PBMC in vitro and in SCID mice. Caution in the use of these agents as antiviral monotherapies is advisable.

Targeted transduction of CD34+ cells by transdominant negative Rev-expressing retrovirus yields partial anti-HIV protection of progeny macrophages.

Congenitally acquired HIV infection may be uniquely suited to treatment via genetic engineering of CD34+ hematopoietic stem/progenitor cells. However, current technologies yield only a small percentage of mature cells that carry the inserted genes, and expression is frequently suppressed. Since clinical trials employing these methodologies have been proposed for anti-HIV gene therapy of HIV-infected children, we wished to assess, by in vitro modeling, the expected limits of transduction efficiency, expression, and antiviral activity using currently available methods. We measured retrovirus-mediated transduction in cord blood progenitors and their in vitro-derived progeny macrophages by Mo-MuLV vectors expressing a transdominant negative Rev (RevTD). CFU-GM transduction efficiency ranged from 7 to 85%, with an average of 28%. Semiquantitative DNA PCR demonstrated < or =100 vector sequence copies per 1000 cells in monocyte/macrophage cultures, which were grown without selection to better model in vivo conditions. When challenged with the macrophagetropic HIV-1BaL isolate, cultured macrophages from mock-transduced CFU-GM colonies supported infection in eight of eight experimental cultures, control LXSN-transduced progenitors supported infection in six of eight cultures, while macrophages derived from RevTD-transduced CFU-GM colonies supported infection in four of eight cultures. Although these results support the ability of neo(r) retroviral vectors containing RevTD to inhibit HIV replication, they indicate that further optimization of transduction efficiency and sustained expression will be required for effective anti-HIV protection in vivo.

Safety and effects of interleukin-2 plus zidovudine in asymptomatic individuals infected with human immunodeficiency virus.

The safety of continuous i.v. interleukin-2 (IL-2) in conjunction with zidovudine (ZDV) was assessed in asymptomatic patients infected with human immunodeficiency virus. Clinical, immunologic, and viral parameters were monitored in a phase I/II trial with dose escalation and crossover arms. Daily doses of IL-2 from 1.5 to 12 x 10(6) IU/m2 were well tolerated and, in the presence of ZDV, did not induce increases in p24 antigenemia. Significant (p less than 0.05) but transient increases in CD4 cells were observed midway through infusion of IL-2 at all doses, and increases in natural and lymphokine-activated killer activity were seen at higher doses. Circulating hypodense eosinophils and soluble IL-2 receptors increased more than 10-fold. Of nine patients available for long-term follow up 13-25 months from baseline and 4-21 months after stopping IL-2, six still had improved CD4 counts (versus baseline), and the mean increase (135/mm3) for all nine patients was significant (p less than 0.05). Eight of these nine patients were negative for serum p24 at the start of therapy, and none had become p24 antigenemic at long-term follow-up.

Decrease in HIV provirus in peripheral blood mononuclear cells during zidovudine and human rIL-2 administration.

Quantification of human immunodeficiency virus (HIV) proviral DNA in peripheral blood mononuclear cells (PBMC) was performed in 13 HIV-seropositive asymptomatic individuals during 10-24 months by polymerase chain reaction amplification of multiple half-log dilutions of cellular DNA. At enrollment, subjects had a geometric mean titer of 100 copies of HIV provirus per 10(6) PBMC (mean +/- SD, 2 +/- 0.9 log10). In four untreated individuals there was no significant change in provirus levels during a mean period of 13.3 months. In eight patients treated with zidovudine (ZDV) and human recombinant interleukin 2 (rIL-2), HIV provirus copies declined to 13 per 10(6) cells (1.1 +/- 0.8 log10) at the end of the first course of ZDV and rIL-2 at week 20 (p less than 0.01), and to 40 per 10(6) cells (1.6 +/- 0.9 log10) after 12 months of treatment (p less than 0.04). Subsequent courses, which included 12 weeks of ZDV alone or 4 weeks of IL-2 alone, did not significantly change the already depressed provirus copy numbers. Proviral copy number also remained depressed during drug-free "washout periods" between courses. Finally, we observed a return to a geometric mean of 400 copies per 10(6) cells (2.6 +/- 0.3 log10) a mean of 7.9 months after discontinuation of therapy. Measurement of changes in HIV provirus should provide a direct marker for defining antiviral activity of drugs, biologics, and combination therapy.

Lack of correlation between the number of circulating B cells and the concentration of serum antibodies reactive with the HIV-1 envelope glycoprotein.

Cells obtained from the peripheral blood of HIV-infected patients and volunteers immunized with HIV-1 vaccines are commonly used to study anti-viral responses, since lymphocytes from the central lymphoid organs are difficult to obtain. Analyses involving PBMC implicitly assume that circulating B cells provide an accurate reflection of the systemic humoral response induced by the HIV antigens. We examined this assumption by comparing the number of B cells secreting IgG anti-gp160/120 antibodies in the peripheral circulation with serum antibody titers. Results indicate that neither the magnitude nor duration of the serologic response detected in HIV-infected patients or gp160/gp120-immunized volunteers reproducibly correlates with the number of B cells secreting anti-envelope antibodies in the blood.

Predominance of defective proviral sequences in an HIV + long-term non-progressor.

We examined the accessory genes and envelope V3 region of provirus obtained over a 5 year period from an HIV+ long-term non-progressor with very low viral load and no in vitro recoverable virus during that same time span. LTR sequences supported normal Tat-mediated promoter activity. Multiple clones of nef sequences were highly conserved with < 10% containing frame shift or stop codon mutations. Functional analysis of the predominant nef sequence indicated wild type downregulation of surface CD4 and good function in a complementation infectivity assay. By contrast, inactivating mutations were found in 64% of amplicons containing vif, vpr, vpu, tat1, and rev1, and in 41% of amplicons containing env V3. Identical inactive sequences were obtained at an interval of 2 years, suggesting persistence of quiescent defective provirus in a long-lived clonal cell population. Furthermore, genetic distance versus time analysis revealed an absence of progressive evolution or arborization of quasispecies over time. This contrasts with data generated from other asymptomatic HIV+ individuals. The non-progressive pattern of env sequence diversity and low R2 for genetic divergence over time suggests that the defective provirus circulating in the periphery of this patient represents a randomly sampled 'fossil record' of earlier replication competent HIV-1 genomes.

Failure of insulin-like growth factor type I to suppress HIV type 1 in adult or umbilical cord mononuclear blood cells.

Insulin-like growth factor type I (IGF-I) has been used as a treatment for cachexia in adults with AIDS and has been reported to show inhibitory activity against HIV-1IIIB in cord blood mononuclear cells (CBMCs) in vitro at low-concentration (1%) fetal bovine serum (FCS). We evaluated the effect of IGF-I on MN, IIIB, and BaL strains, as well as on a patient isolate of HIV-1 in CBMCs and adult peripheral blood mononuclear cells (PBMCs). IGF-I failed to show any inhibitory effect on HIV replication in CBMCs or adult PBMCs under various culture conditions. In contrast to an earlier report of an antiviral effect, IGF-I augmented HIV-1 replication in PHA-stimulated PBMCs maintained in a low concentration of FCS.

Advancing AIDSVAX to phase 3. Safety, immunogenicity, and plans for phase 3.

AIDSVAX (VaxGen, Inc., South San Francisco, CA), a possible vaccine to protect against human immunodeficiency virus type 1 (HIV-1) infection, is being tested for efficacy in phase 3 studies. It has been tested for potential efficacy in chimpanzees, and tested for safety and immunogenicity in human clinical studies. Four candidate vaccines, each with a different envelope protein antigen or combination of antigens, have been produced in alum formulations. In both design and clinical testing, AIDSVAX has an excellent safety profile. Because these highly purified proteins were prepared using recombinant DNA technology, there is no possibility of these vaccines causing HIV infection. Having been administered to over 1200 people, the only side effects attributable to AIDSVAX have been local pain and inflammation at the injection site. After immunization, essentially all recipients developed a robust antibody response, including binding and neutralizing antibodies. The neutralizing antibodies peaked after a 12-month boost. Excellent memory is induced. Two phase 3 trials of two bivalent formulations will evaluate their efficacy. One trial will use a bivalent subtype B formulation. This trial in North America will involve 5000 men who have sex with men and heterosexual women at high risk. The other study will use a bivalent subtype B/subtype E formulation. This trial in Thailand and will involve 2500 intravenous drug users. Both studies will be randomized, double-blinded and placebo controlled. The volunteers will be followed for 3 years. The end points of the studies are infection, as defined by seroconversion to standard diagnostic tests, and viral load, as defined by commercial polymerase chain reaction (PCR) tests.

Immunization with recombinant canarypox vectors expressing membrane-anchored glycoprotein 120 followed by glycoprotein 160 boosting fails to generate antibodies that neutralize R5 primary isolates of human immunodeficiency virus type 1.

Antibodies generated by candidate HIV-1 vaccines in a phase I clinical trial were assessed for neutralizing activity with a panel of eight well-characterized, genetically diverse clade B primary isolates having an R5 phenotype. The vaccines consisted of one of three different recombinant canarypox vectors expressing membrane-anchored HIV-1(MN)gp120 (ALVAC vCP205, vCP1433, and vCP1452) followed by boosting with a soluble gp160 hybrid consisting of MNgp120 and the majority of gp41 from strain IIIB. Serum samples from a subset of volunteers in each arm of the trial, containing moderate to high titers of neutralizing antibodies to HIV-1 MN, were analyzed. Competition assays with peptides revealed that the majority of neutralizing activity was specific for the MN-V3 loop. Despite MN-specific neutralization titers that sometimes exceeded 1:500, no neutralization of primary isolates was detected and, in some cases, mild infection enhancement was observed. In addition, little or no neutralization of the HIV-1 IIIB heterologous T cell line-adapted strain of virus was detected. These results reinforce the notion that monovalent HIV-1 ENV is a poor immunogen for generating cross-reactive neutralizing antibodies.

Safety profile of phase I and II preventive HIV type 1 envelope vaccination: experience of the NIAID AIDS Vaccine Evaluation Group.

The NIAID-sponsored AIDS Vaccine Evaluation Group was established in 1988 to perform phase I/II clinical trials with candidate preventive HIV-1 vaccines. This report includes safety data from 1398 HIV-negative, healthy volunteers who were enrolled into 25 phase I and 1 phase H multicentered, randomized, double-blind studies evaluating seven recombinant HIV-1 envelope vaccines, two V3 loop synthetic peptide vaccines, and two live poxvirus-vectored recombinant envelope vaccines. All studies but three were placebo controlled; the placebo was either the adjuvant alone or, in studies of recombinant poxvirus vaccines, it was the vector with no gene insert or a non-HIV gene insert. All candidate vaccines were generally well tolerated. The only adverse effects that were clearly related to vaccination were occasional acute local and systemic reactions that were associated with the adjuvants. Three adjuvants in particular were associated with moderate to severe local reactions: alum plus deoxycholate (ImmunoAg), MTP-PE (Biocine Corp.), and QS21 (Genentech, Inc.). MTP-PE was also associated with self-limited severe systemic reactions. There were no serious adverse laboratory toxicities and no evidence of significant immunosuppressive events after receipt of the candidate vaccines. A few volunteers experienced symptoms that might relate to an underlying immunopathologic mechanism (rash, hemolytic anemia, arthralgia), but their presentations were mild and their incidence was low. Eleven volunteers were diagnosed with malignancies during or after their participation, which was within the 95% confidence interval of the number of cases predicted by the National Cancer Institute SEER (Program for cancer surveillance, epidemiology, and end result reporting) database. In conclusion, the envelope-based recombinant or synthetic candidate HIV-1 vaccines appear to be safe and this work has prepared the way for the testing of increasingly complex candidate HIV-1 vaccines.

A peptide enzyme linked immunosorbent assay (ELISA) for the detection of human immunodeficiency virus type-2 (HIV-2) antibodies: an evaluation on polymerase chain reaction (PCR) confirmed samples.

BACKGROUND: HIV-1 and HIV-2 infections differ in prognosis, and may also require different prevention and/or treatment approaches. Thus, estimating the true prevalence of HIV-1 and HIV-2 infections, as well as co-infections, is a critical step in controlling the disease. There are a few commercial ELISA and immunoblot kits, which can differentiate between HIV-1 and HIV-2 infections. However, some of these assays overestimate the prevalence of dual infection. Hence, it is necessary to develop assays capable of discriminating between the two infections. OBJECTIVES: To develop a synthetic HIV-2 env based peptide ELISA for the detection of HIV-2 specific antibodies and evaluate its performance on samples from HIV positive individuals previously tested by HIV-1 and HIV-2 PCR and HIV seronegative individuals. STUDY DESIGN: We studied 45 HIV seronegative and 63 HIV infected individuals, including 30 HIV-1 PCR and immunoblot positives, 19 HIV-2 PCR and immunoblot positives, five HIV-1 and two PCR and dual immunoblot positives, two PCR negative but positive for HIV-2 by immunoblot and seven dual immunoblot positives who were only positive for HIV-1 by PCR. RESULTS: All 24 HIV-2 PCR positive samples tested were positive by the peptide assay. Among 30 HIV-1 PCR and immunoblot positive samples, only one (3.3%) showed an absorbance value above the cut off level. The seven dual positive samples by immunoblot (only positive for HIV-1 by PCR) were negative by the HIV-2 peptide ELISA. There was a 100% concordance between HIV-2 PCR and peptide ELISA. The sensitivity, specificity, and the likelihood ratio for the peptide ELISA were 100,94.9, and 19.5, respectively when compared against the PCR findings. CONCLUSIONS: This ELISA, using a specific immunodominant epitope (11 amino acids) from the transmembrane (gp36) portion of the HIV-2 envelope glycoprotein showed a high concordance with PCR findings. This can be considered as a highly sensitive, specific and economically feasible assay for the discrimination of HIV-1 and HIV-2, and may serve as an alternative to HIV-2 PCR in epidemiological studies.

Microdialysis studies of brain norepinephrine, serotonin, and dopamine release during ingestive behavior. Theoretical and clinical implications.

This minireview deals with the possible roles of monoamines in feeding and feeding disorders. The introduction sketches the results of earlier studies with local drug injections and selective neurotoxins which provided pharmacological evidence that monoamines can influence food intake and body weight. A table summarizing this evidence is used to list monoamine changes that could underlie anorexia or hyperphagia. It is apparent that abnormalities in the monoamines, along with their cotransmitters, could cause many forms of feeding disorder. It is proposed as a working hypothesis that several varieties of hyperphagia leading to obesity have a common element. This common factor is a change in excitability of a lateral hypothalamic reinforcement system as manifested in self-stimulation at a stimulation-bound feeding site. Understanding this feeding reward-aversion system helps us understand hyperphagia and anorexia. The neurochemistry of reward and aversion involves the monoamines. This paper focuses on dopamine and serotonin. The data support the hypothesis that dopamine systems projecting to the nucleus accumbens and other forebrain areas from the mid-brain ventral tegmental area (VTA) are important for approach and positive reinforcement in ingestive behavior and self-stimulation. Serotonin is hypothesized to facilitate satiety and inhibition of feeding reward in the hypothalamus. The next section abstracts our recent experiments that measured pharmacological and physiological release of the monoamines in the hypothalamus and nucleus accumbens during ingestive behavior and self-stimulation. In vivo microdialysis in freely moving rats suggested the following: (1) Norepinephrine was released in the paraventricular nucleus during the active, feeding period of the circadian cycle. (2) The serotonin metabolite 5-HIAA also increased in the PVN at the same time if there was food to eat. (3) Amphetamine infused into the lateral hypothalamus (LH) by reverse dialysis increased synaptic dopamine, norepinephrine, and serotonin. (4) The anorectic drug d-fenfluramine increased synaptic serotonin in the LH and also increased the dopamine metabolite DOPAC, suggesting that serotonin and dopamine in the LH might contribute to fenfluramine-induced satiety. Local d-fenfluramine injection into the LH or local infusion by reverse dialysis again increased serotonin and decreased 5-HIAA and interfered with local dopamine metabolism as reflected in decreased DOPAC and HVA. (5) Tryptophan, a serotonin precursor, given systemically at an anorectic dose, increased extracellular serotonin in the LH, but this effect was only detectable in food-deprived rats. This was seemingly pH independent (between 5.8 and 8). The passage other cations through CFo is strictly suppressed (even at pH 8 and with 300 mM NaCl in the medium).(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulus-evoked changes in neostriatal dopamine levels in awake and anesthetized rats as measured by microdialysis.

The effect of medial forebrain bundle (MFB) stimulation on neostriatal dopamine levels was examined using in vivo microdialysis in urethane-anesthetized and awake, freely-moving rats in conjunction with single unit extracellular recordings from antidromically identified nigral dopaminergic neurons. Dialysis samples were collected during baseline periods or while stimulating the MFB with trains of 5 or 10 pulses at different frequencies within a physiologically relevant range. When the perfusion solution contained 1.2 mM Ca2+, even intense, high frequency stimulation was ineffective at producing significant elevations in neostriatal dopamine levels whereas cocaine or amphetamine reliably caused several-fold elevations in dopamine levels. When the perfusate contained 2.4 mM Ca2+, modest MFB stimulation within the range of spontaneous nigral cell firing produced large and reliable increases in dopamine levels. There was a significant correlation between the proportion of dopaminergic neurons that could be antidromically activated from the MFB and the increase in neostriatal dopamine. There was no effect of stimulus pattern on the increase in dopamine levels, and results obtained in awake, freely-moving animals did not differ from those obtained in anesthetized animals. These data provide good evidence that in vivo microdialysis is sensitive to neostriatal dopamine overflow evoked by stimulation within the normal rate of firing of nigrostriatal neurons and that Ringer's Ca2+ concentration is a critical variable in the detection of stimulus-induced release of dopamine.

Feeding increases extracellular serotonin in the lateral hypothalamus of the rat as measured by microdialysis.

Microdialysis probes inserted into chronically implanted guide shafts allowed the collection of serotonin and 5-hydroxyindoleacetic acid (5-HIAA) from the lateral hypothalamus of rats during feeding behavior. After the collection of baseline samples, animals were offered a palatable diet that they could only see and smell for 60 min, then they were allowed access to the food for an hour. An additional three samples were collected after food was removed. Extracellular serotonin increased during the first half hour of access when the animals actually ate the food, and then returned to baseline level throughout the remainder of the test. 5-HIAA decreased gradually with no increase during feeding. These data suggest that eating a meal of palatable food causes a short-term increase in extracellular serotonin in the lateral hypothalamus. This increased serotonin may play a role in the control of lateral hypothalamic feeding and reward.

Serotonin release in lateral and medial hypothalamus during feeding and its anticipation.

In the present experiments we extend previous findings that established a relationship between feeding behavior and hypothalamic serotonin as measured by in vivo microdialysis. The new result is hypothalamic release of serotonin in anticipation of eating when the animal sees and smells food. We have now verified brain serotonin peaks in four different ways: 1) a serotonergic reuptake blocker (fluoxetine 1 or 10 microM) in the perfusion medium raised basal levels of serotonin, 2) every sample was oxidized at two potentials using a dual potentiostat to confirm the voltage characteristics of each peak, 3) serotonin peaks were reduced by the selective serotonin cell body agonist, 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), thus helping confirm that most of the serotonin observed in these experiments was neuronal in origin, and 4) lateral and medial hypothalamic microdialysis probes were used simultaneously to monitor the degree of diffusion from one to the other. The results show that extracellular serotonin increases at both sites during preingestive events as well as during eating, but not afterwards.