Prefrontal expectancy and reinforcement-driven antidepressant placebo effects

Placebo responses in depression exemplify how expectancies and appraisals impact mood. Cognitive and neural mechanisms underlying these responses are still poorly understood, partly due to the difficulty of simulating antidepressant effects and manipulating mood experimentally. To address these challenges, we developed an acute antidepressant placebo experiment involving the intravenous administration of a "fast-acting antidepressant" and a trial-by-trial sham fMRI "neurofeedback" manipulation, purporting to reveal mood-relevant neural responses. Twenty volunteers with major depression underwent this experiment while rating their expected and actual mood improvement. Mixed-effects analyses of trial-by-trial ratings revealed that the "drug" infusion cues induced higher expectancies of mood improvement, while both the "drug" infusion cue and the sham neurofeedback induced a reported mood improvement. Neurofeedback of greater magnitude, compared to lower magnitude, recruited the lateral prefrontal cortex (lPFC). Individuals with greater lPFC responses to neurofeedback displayed: (1) greater effect of previous mood improvement on expectancy ratings and (2) greater effect of sham neurofeedback on mood improvement. Behavioral antidepressant placebo effects were additionally moderated by changes in peripheral β-endorphin plasma levels and depressive symptomatology. These data demonstrate the feasibility of trial-by-trial manipulation of antidepressant placebo-associated expectancies and their reinforcement. We provide initial insights into the role of the lPFC in the interplay between placebo-induced expectancies and mood, as well as preliminary evidence for the role of the opioid system in antidepressant placebo effects.

Smoking history, and not depression, is related to deficits in detection of happy and sad faces

INTRODUCTION

Previous research has demonstrated that chronic cigarette smoking and major depressive disorder (MDD) are each associated with cognitive decrements. Further, these conditions co-occur commonly, though mechanisms in the comorbid condition are poorly understood. There may be distinct, additive, or overlapping factors underlying comorbid cigarette smoking and MDD. The present study investigated the impact of smoking and MDD on executive function and emotion processing.

METHODS

Participants (N=198) were grouped by diagnostic category (MDD and healthy controls, HC) and smoking status (ever-smokers, ES and never-smokers, NS). Participants completed the Facial Emotion Perception Test (FEPT), a measure of emotional processing, and the parametric Go/No-go task (PGNG), a measure of executive function.

RESULTS

FEPT performance was analyzed using ANCOVA with accuracy and reaction time as separate dependent variables. Repeated measures MANCOVA was conducted for PGNG with performance measure and task level as dependent variables. Analyses for each task included diagnostic and smoking group as independent variables, and gender was controlled for. Results for FEPT reveal that lower overall accuracy was found for ES relative to NS, though MDD did not differ from HC. Post-hoc analyses revealed that ES were poorer at identifying happy and sad, but not fearful or angry, faces. For PGNG, poorer performance was observed in MDD relative to HC in response time to Go targets, but there were no differences for ES and NS. Interaction of diagnosis and smoking group was not observed for performance on either task.

CONCLUSIONS

The results of this study provide preliminary evidence for distinctive cognitive decrements in smokers and individuals with depression.

Long-term estrogen replacement is associated with improved nonverbal memory and attentional measures in postmenopausal women

OBJECTIVE

To determine the cognitive domains improved or preserved by long-term hormone replacement therapy (HRT).

DESIGN

A comprehensive neuropsychological test battery was administered to healthy postmenopausal women who had been treated or not treated with long-term HRT without interruption since menopause.

SETTING

Women were recruited by advertisement from a university town and surrounding areas.

PATIENT(S)

Women 60 years or older were studied who were treated (n = 16) or not treated (n = 13) with HRT.

INTERVENTION(S)

Neuropsychological testing included tests of memory, verbal fluency, executive functions, attention and concentration, and psychomotor function. Tests of intellectual function, depressive symptoms, and emotional functioning assessed general functions and comparability of the groups.

MAIN OUTCOME MEASURE(S)

Neuropsychological testing scores were compared between groups.

RESULT(S)

No statistically significant differences between the groups were found for general demographic, intellectual, and psychological measures. Scores from both the Weschler Memory Scale Visual Reproduction (delayed recall) and the Digit Vigilance Test (attention) showed statistically significant better performance and fewer errors in the group of women on HRT.

CONCLUSION(S)

Long-term postmenopausal HRT is associated with higher scores in tests of nonverbal memory and attention.

Neuroimaging of aging and estrogen effects on central nervous system physiology

OBJECTIVE

To review the literature on neuroimaging studies focusing on gender differences in the aging process and on the effects of postmenopausal estrogen use on the brain.

DESIGN

Pertinent studies were identified through a computer MEDLINE search. References of selected articles were hand-searched for additional citations.

CONCLUSION(S)

The current literature suggests that estrogen replacement may decrease brain white matter lesions, increase cerebral blood flow, alter regional brain activation patterns during cognitive processing, and have modulatory effects on various neurotransmitter systems. Overall, this points to a functional plasticity in higher order brain processing that can be altered by gonadal steroids.

Solid-state coordination chemistry: structural influences of copper-phenanthroline subunits on oxovanadium organophosphonate phases. hydrothermal synthesis and structural characterization of the two-dimensional materials [Cu(phen)(VO)(O3PCH2PO3)(H2O)], [[Cu(phen)]2(V2O5)(O3PCH2CH2PO3)], and [[Cu(phen)]2(V3O5)(O3PCH2CH2CH2PO3)2(H2O)] and the three-dimensional phase [[Cu(phen)]2(V3O5)(O3PCH2PO3)2(H2O)]

The hydrothermal reactions of CuCl2*2H2O, Na3VO4, 1,10-phenanthroline, and the appropriate organodiphosphonate ligand yield [Cu(phen)(VO)(O3PCH2PO3)(H2O)] (1), [[Cu(phen)]2(V2O5)(O3PCH2CH2PO3)] (2), [[Cu(phen)]2(V3O5)(O3PCH2CH2CH2PO3)2 (H2O)] (3), and [[Cu(phen)]2(V3O5)(O3PCH2PO3)2(H2O)] (4). Compounds 1-3 exhibit two-dimensional structures. The structures exhibit distinct vanadium building blocks: square pyramidal, mononuclear V(IV) sites in 1, a binuclear unit of corner-sharing V(V) tetrahedra in 2, and a trinuclear unit of corner-sharing V(V) square pyramids and a V(IV) octahedron in 3. The network structures of 1 and 2 are constructed from one-dimensional oxovanadium-diphosphonate chains linked by Cu(II) square pyramids into two-dimensional layers. In contrast, compound 3 exhibits a two-dimensional oxovanadium-organodiphosphonate network, with Cu(II) sites decorating the surfaces. Compound 4 is unique in exhibiting a framework structure, which may be described as a three-dimensional oxovanadium-organodiphosphonate substructure with [Cu(phen)]2+ subunits covalently attached to the surface of channels running parallel to the a-axis. The magnetic properties of 1-4 are also correlated to the structural characteristics. The magnetic behavior of 2 is thus dominated by antiferromagnetic interactions. The magnetic behavior of 1 and 4 is consistent with the presence of two distinct paramagnetic metal ions, Cu(II) and V(IV). In contrast, 3 does not exhibit ferrimagnetic behavior, but rather weak antiferromagnetic coupling. Crystal data: 1, C13H10N2CuP2VO8, monoclinic P2(1)/c, a = 9.0656(5) A, b = 8.6584(5) A, c = 20.934(1) A, beta = 97.306(1) degrees, Z = 4; 2, C26H20N4Cu2P2V2O11, triclinic P1, a = 10.6096(5) A, b = 11.6951(5) A, c = 13.1796(6) A, alpha = 71.369(1) degrees, beta = 70.790(1) degrees, gamma = 80.738(1) degrees, Z = 2; 3, C30H28N4Cu2P4V3O18, triclinic P1, a = 9.4356(6) A, b = 10.6556(6) A, c = 11.0354(7) A, alpha = 118.187(1) degrees, beta = 91.416(1) degrees, gamma = 107.821(1) degrees, Z = 1; 4, C26H20N4Cu2P4V3O18, monoclinic, P2(1)/c a = 8.3947(3) A, b = 16.8401(7) A, c = 11.9144(5) A, beta = 93.903(1) degrees, Z = 2.

Regional mu opioid receptor regulation of sensory and affective dimensions of pain

The endogenous opioid system is involved in stress responses, in the regulation of the experience of pain, and in the action of analgesic opiate drugs. We examined the function of the opioid system and mu-opioid receptors in the brains of healthy human subjects undergoing sustained pain. Sustained pain induced the regional release of endogenous opioids interacting with mu-opioid receptors in a number of cortical and subcortical brain regions. The activation of the mu-opioid receptor system was associated with reductions in the sensory and affective ratings of the pain experience, with distinct neuroanatomical involvements. These data demonstrate the central role of the mu-opioid receptors and their endogenous ligands in the regulation of sensory and affective components of the pain experience.

Regional cerebral blood flow effects of nicotine in overnight abstinent smokers

BACKGROUND

Most people agree that dependence to tobacco is mediated by the effects of nicotine on the central nervous system, albeit the neural pathways involved are not clearly delineated. We investigated the effect of nasal nicotine spray on regional cerebral blood flow (rCBF) in a sample of habitual smokers, with H2 15O and positron emission tomography (PET).

METHODS

Eighteen volunteer smokers were studied after 12 hours of smoking deprivation. Regional cerebral blood flow measures were obtained with PET and 50 mCi H2 15O in six consecutive scans. Nicotine spray and a placebo spray were administered in a single-blind design, preceded and followed by baseline studies. Images were coregistered and anatomically standardized. Square (9-mm side) regions of interest were placed in 10 preselected brain regions, bilaterally. The effects of the experimental condition and gender were tested with two-way repeated-measures analysis of variance in each of the regions studied.

RESULTS

Nicotine reduced rCBF in the left anterior temporal cortex and in the right amygdala. Increases were noted in the right anterior thalamus.

CONCLUSIONS

In habitual smokers after overnight abstinence, nicotine induced differing effects on regional blood flow relative to whole brain blood flow. Increases were observed in the thalamus, a region rich in nicotinic receptors, and reductions in limbic and paralimbic (amygdala, anterior temporal cortex) regions.

Cognitive function in euthymic bipolar I disorder

Recent reports have suggested the presence of persistent cognitive impairments in patients diagnosed with Bipolar Disorder even after prolonged euthymic phases. In this work, various domains of cognitive function were examined in asymptomatic patients diagnosed with Bipolar I Disorder (BDI) in comparison with healthy subjects. Fifteen otherwise healthy BDI patients with a prior history of psychosis during mania completed a neuropsychological testing battery after a prolonged asymptomatic remission. Their scores were compared to those of individually matched healthy subjects with unpaired two-tailed t-tests at P<0.01. Relationships between cognitive performance measures and clinical variables related to illness severity were also examined with Pearson correlations, P<0.05. We detected poorer performance on measures of verbal learning, executive functioning and motor coordination in BDI patients compared to control volunteers. Scores on tests of executive functioning were negatively correlated with the number of episodes of mania and depression. Social and occupational scores were also associated with a poorer performance on measures of verbal learning and executive function. Euthymic BDI patients, therefore, demonstrate reductions in specific cognitive domains even after prolonged asymptomatic phases. Some of these deficits appear to be associated with a more severe course of illness and poorer social and occupational functioning.

Copper(I) complexes, copper(I)/O(2) reactivity, and copper(II) complex adducts, with a series of tetradentate tripyridylalkylamine tripodal ligands

Copper(I) and copper(II) complexes possessing a series of related ligands with pyridyl-containing donors have been investigated. The ligands are tris(2-pyridylmethyl)amine (tmpa), bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine (pmea), bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine (pmap), and tris[2-(2-pyridyl)ethyl]amine (tepa). The crystal structures of the protonated ligand H(tepa)ClO(4), the copper(I) complexes [Cu(pmea)]PF(6) (1b-PF(6)), [Cu(pmap)]PF(6) (1c-PF(6)), and copper(II) complexes [Cu(pmea)Cl]ClO(4).H(2)O (2b-ClO(4).H(2)O), [Cu(pmap)Cl]ClO(4).H(2)O (2c-ClO(4).H(2)O), [Cu(pmap)Cl]ClO(4) (2c-ClO(4)), and [Cu(pmea)F](2)(PF(6))(2) (3b-PF(6)) were determined. Crystal data: H(tepa)ClO(4), formula C(21)H(25)ClN(4)O(4), triclinic space group P1, Z = 2, a = 10.386(2) A, b = 10.723(2) A, c = 11.663(2) A, alpha = 108.77(3) degrees, beta = 113.81(3) degrees, gamma = 90.39(3) degrees; 1b-PF(6), formula C(19)H(20)CuF(6)N(4)P, orthorhombic space group Pbca, Z = 8, a = 14.413(3) A, b = 16.043(3) A, c = 18.288(4) A, alpha = beta = gamma = 90 degrees; (1c-PF(6)), formula C(20)H(22)CuF(6)N(4)P, orthorhombic space group Pbca, Z = 8, a = 13.306(3) A, b = 16.936(3) A, c = 19.163(4) A, alpha = beta = gamma = 90 degrees; 2b-ClO(4).H(2)O, formula C(19)H(22)Cl(2)CuN(4)O(5), triclinic space group P1, Z = 4, a = 11.967(2) A, b = 12.445(3) A, c = 15.668(3) A, alpha = 84.65(3) degrees, beta = 68.57(3) degrees, gamma = 87.33(3) degrees; 2c-ClO(4).H(2)O, formula C(20)H(24)Cl(2)CuN(4)O(5), monoclinic space group P2(1)/c, Z = 4, a = 11.2927(5) A, b = 13.2389(4) A, c = 15.0939(8) A, alpha = gamma = 90 degrees, beta = 97.397(2) degrees; 2c-ClO(4), formula C(20)H(22)Cl(2)CuN(4)O(4), monoclinic space group P2(1)/c, Z = 4, a = 8.7682(4) A, b = 18.4968(10) A, c = 13.2575(8) A, alpha = gamma = 90 degrees, beta = 94.219(4) degrees; 3b-PF(6), formula [C(19)H(20)CuF(7)N(4)P](2), monoclinic space group P2(1)/n, Z = 2, a = 11.620(5) A, b = 12.752(5) A, c = 15.424(6) A, alpha = gamma = 90 degrees, beta = 109.56(3) degrees. The oxidation of the copper(I) complexes with dioxygen was studied. [Cu(tmpa)(CH(3)CN)](+) (1a) reacts with dioxygen to form a dinuclear peroxo complex that is stable at low temperatures. In contrast, only a very labile peroxo complex was observed spectroscopically when 1b was reacted with dioxygen at low temperatures using stopped-flow kinetic techniques. No dioxygen adduct was detected spectroscopically during the oxidation of 1c, and 1d was found to be unreactive toward dioxygen. Reaction of dioxygen with 1a-PF(6), 1b-PF(6), and 1c-PF(6) at ambient temperatures leads to fluoride-bridged dinuclear copper(II) complexes as products. All copper(II) complexes were characterized by UV-vis, EPR, and electrochemical measurements. The results manifest the dramatic effects of ligand variations and particularly chelate ring size on structure and reactivity.

Hydrothermal Syntheses and Structural Characterizations of Organic−Inorganic Hybrid Materials of the M(II)−Ligand/Vanadium Oxide System (M(II) = Cu(II) and Zn(II); Ligand = 2,2‘-Bipyridine and 2,2‘:6‘,2‘ ‘-Terpyridine)

Investigation into the incorporation of complex transition metal-organic units into vanadium oxide structures has resulted in the preparation of several novel composite materials. Hydrothermal reactions of V(2)O(5), 2,2'-bipyridine, an appropriate Zn or Cu starting material, and H(2)O under a variety of conditions yielded the organic-inorganic hybrid materials [[Zn(2,2'-bpy)](2)V(4)O(12)] (1) and [Cu(2,2'-bpy)V(4)O(10.5)] (2). Blocking an additional coordination site on the secondary metal center by using a tridentate organonitrogen ligand, 2,2':6',2' '-terpyridine in place of 2,2'-bipyridine, allowed the isolation of [Cu(terpy)V(2)O(6)] (3) and [[Zn(terpy)](2)V(6)O(17)] (4). The structure of 1 is a two-dimensional zinc vanadate layer, composed of rings containing four corner-sharing [VO(4)] vanadium(V) tetrahedra linked through six zinc square pyramids, with the 2,2'-bipyridine groups attached to the zinc centers and directed above and below the plane of the layer. In contrast to 1, the layer of 2 is based on a two-dimensional vanadium oxide substructure composed of vanadium(IV) square pyramids and vanadium(V) tetrahedra with copper square pyramids attached through corner-sharing interactions with vanadium tetrahedra such that the bipyridine ligands attached to the copper sites form staggered stacks above and below the plane of the layer. Compound 3 consists of one-dimensional vanadium oxide chains of corner-sharing tetrahedra linked through copper-terpyridine units into a two-dimensional bimetallic oxide of composition [CuV(2)O(6)], while the layer structure of 4 contains more complex one-dimensional vanadium oxide chains composed of fused rings of six corner-sharing vanadium oxide tetrahedra which are linked into a layer through [Zn(terpy)](2+) units.

Assessment of muscarinic receptor concentrations in aging and Alzheimer disease with [11C]NMPB and PET

Cerebral cholinergic deficits have been described in Alzheimer disease (AD) and as a result of normal aging. At the present time, there are very limited options for the quantification of cholinergic receptors with in vivo imaging techniques such as PET. In the present study, we examined the feasibility of utilizing [11C]N-methyl-4-piperidyl benzilate (NMPB), a nonselective muscarinic receptor ligand, in the study of aging and neurodegenerative processes associated with cholinergic dysfunction. Based on prior data describing the accuracy of various kinetic methods, we examined the concentration of muscarinic receptors with [11C]NMPB and PET using two- and three-compartment kinetic models. Eighteen healthy subjects and six patients diagnosed with probable AD were studied. Pixel-by-pixel two-compartment model fits showed acceptable precision in the study of normal aging, with comparable results to those obtained with a more complex and less precise three-compartment model. Normal aging was associated with a reduction in muscarinic receptor binding in neocortical regions and thalamus. In AD patients, the three-compartment model appeared capable of dissociating changes in tracer transport from changes in receptor binding, but suffered from statistical uncertainty, requiring normalization to a reference region, and therefore limiting its potential use in the study of neurodegenerative processes. After normalization, no regional changes in muscarinic receptor concentrations were observed in AD.

Effects of nicotine on regional cerebral glucose metabolism in awake resting tobacco smokers

Eleven healthy tobacco smoking adult male volunteers of mixed race were tobacco abstinent overnight for this study. In each subject, positron emission tomographic images of regional cerebral metabolism of glucose with [18F]fluorodeoxyglucose were obtained in two conditions in the morning on different days: about 3min after approximately 1-2mg of nasal nicotine spray and after an equivalent volume of an active placebo spray of oleoresin of pepper in a random counterbalanced design. A Siemens/CTI 931/08-12 scanner with the capability of 15 horizontal brain slices was used. The images were further converted into a standard uniform brain format in which the mean data of all 11 subjects were obtained. Images were analysed in stereotactic coordinates using pixel-wise t statistics and a smoothed Gaussian model. Peak plasma nicotine levels varied three-fold and the areas under the curve(0-30min) varied seven-fold among the individual subjects. Nicotine caused a small overall reduction in global cerebral metabolism of glucose but, when the data were normalized, several brain regions showed relative increases in activity. Cerebral structures specifically activated by nicotine (nicotine minus pepper, Z score >4.0) included: left inferior frontal gyrus, left posterior cingulate gyrus and right thalamus. The visual cortex, including the right and left cuneus and left lateral occipito-temporal gyrus fusiformis, also showed an increase in regional cerebral metabolism of glucose with Z scores >3. 6. Structures with a decrease in regional cerebral metabolism of glucose (pepper minus nicotine) were the left insula and right inferior occipital gyrus, with Z scores >3.5. Especially important is the fact that the thalamus is activated by nicotine. This is consistent with the high density of nicotinic cholinoceptors in that brain region. However, not all brain regions affected by nicotine are known to have many nicotinic cholinoceptors. The results are discussed in relation to the cognitive effects of nicotine.

Hydrothermal synthesis of organic-inorganic hybrid materials: network structures of the bimetallic oxides [M(Hdpa)2V4O12] (M = Co, Ni, dpa = 4,4'-dipyridylamine)

The hydrothermal reactions of MCl(2).6H2O (M = Co, Ni) NaVO3, 4,4'-dipyridylamine (dpa), and H2O yield materials of the type [M(Hdpa)2V4O12] (M = Co (1), Ni (2)). The two-dimensional structures of 1 and 2 are constructed from bimetallic oxide networks (MV4O12)n2n- with monodentate Hdpa projecting the protonated ring into the interlamellar region. The oxide network may be described as ruffled chains of corner-sharing (VO4) tetrahedra linked by (NiO4N2) octahedra into the two-dimensional assembly. Crystal data: C10H10Co0.5N3O6V2(1), monoclinic P2(1)/c, a = 10.388(1) A, b = 7.6749(7) A, c = 16.702(2) A, beta = 102.516(1) degrees, Z = 4. C10H10N3Ni0.5O6V2 (2), monoclinic, P2(1)/c, c = 10.3815(2) A, b = 7.7044(2) A, c = 16.6638(4) A, beta = 102.573(1) degrees, Z = 4.

Effects of long-term hormone therapy on cholinergic synaptic concentrations in healthy postmenopausal women

Experimental evidence suggests that gonadal steroids regulate brain neurochemical systems associated with cognitive function, such as the cholinergic system. This study examines the effect of long-term postmenopausal hormone therapy on the brain concentrations of cholinergic synaptic terminals in women using single photon emission computed tomography and the radiotracer [(123)I]iodobenzovesamicol ([(123)I]IBVM). [(123)I]IBVM labels the vesicular acetylcholine transporter (VAChT) located in the presynaptic terminals of these neurons. Sixteen healthy women treated with hormone therapy since the menopause and 12 women not treated with hormones were studied. There were no significant differences in regional IBVM binding indexes between the 2 groups. The length of hormone replacement therapy correlated positively with VAChT binding indexes in multiple cortical areas (P < 0.05): frontal cortex (Spearman rank correlation: rho = 0.79), parietal cortex (rho = 0.62), temporal cortex (rho = 0.80), anterior cingulate (rho = 0.71), and posterior cingulate (rho = 0.63), but not in the basal ganglia (rho = 0.35; P = 0.2). An earlier onset of menopause in hormone-treated women was associated with higher VAChT indexes in the anterior cingulate (rho = -0.56; P = 0.02) and posterior cingulate (rho = -0.63; P = 0.01). The opposite was found in the posterior cingulate of women not treated with hormones (rho = 0.58; P = 0.04). Women treated with estrogen alone also showed higher VAChT indexes than women treated with estrogen and progestin in the posterior cingulate cortex (by Mann-Whitney U test: z = 2.42; P = 0.015). Although an overall effect of postmenopausal hormone therapy was not found, associations between an index of cortical cholinergic terminal concentrations and the length of hormonal replacement suggest that hormone therapy may influence the survival or plasticity of these cells in postmenopausal women. The data also suggest possible differential effects of estrogen and estrogen with progestin treatments in brain areas critical for cognitive processing.

Vesicular monoamine transporter concentrations in bipolar disorder type I, schizophrenia, and healthy subjects

BACKGROUND

Previous analyses of vesicular monoamine transporter (VMAT2) binding in euthymic bipolar disorder type I (BDI) patients have shown increases of this presynaptic marker in the thalamus and ventral midbrain. To assess the diagnostic specificity of those findings, we compared VMAT2 concentrations between euthymic BDI patients, patients diagnosed with schizophrenia (SCH), and age-matched healthy volunteers.

METHODS

Binding sites for VMAT2 were quantified with (+)-alpha-[11C]DTBZ (dihydrotetrabenazine) and positron emission tomography. Fifteen euthymic BDI and 12 SCH patients and 15 group-matched healthy controls were studied. [11C]DTBZ tracer transport and binding potentials were examined in the thalamus and ventral midbrain with factorial analyses of variance and post hoc Tukey's honestly significantly different tests.

RESULTS

Analysis of variance detected diagnosis effects in binding potentials in both brain regions. Binding of VMAT2 in the thalamus was higher in BDI patients than in control subjects and SCH patients. Conversely, ventral brainstem binding was nearly identical between BDI and SCH patients and were higher than in the control group.

CONCLUSIONS

The patterns of regional VMAT2 expression, and by extension, the concentration of monoaminergic synaptic terminals, differ between BDI, SCH, and a control group. These findings may relate to both similarities and differences in the presentation or clinical course of these syndromes and require further examination.

The hydrothermal syntheses and characterization of one- and two-dimensional structures constructed from metal–organic derivatives of polyoxometalates: [{Cu(bpy)2}{Cu(bpy)(H2O)}(Mo5O15){O3P(CH2)4PO3}]·H2O and [{Cu2(tpypyz)(H2O)2}(Mo5O15)(O3PCH2CH2PO3)]·5.5H2O [bpy = 2,2′-bipyridine, tpypyz = tetra(2-pyridyl)pyrazine]

The hydrothermal reaction of CuSO(4).5H2O, Na2MoO(4).2H2O and 2,2'-bipyridine with the bridging diphosphonate ligand H2O3P(CH2)4PO3H2 yields the one-dimensional chain [(Cu(bpy)2)(Cu(bpy)(H2O)2)(Mo5O15)(O3P(CH2)4PO3)].H2O; the introduction of a second bridging component in the reaction of Cu(MeCO2)2.H2O, MoO3, H2O3PCH2CH2PO3H2 and tetra(2-pyridyl)pyrazine yields the network solid [(Cu2(tpypyz)(H2O)2)(Mo5O15)(O3PCH2CH2PO3)].5.5H2O.

Solid state coordination chemistry: construction of 2D networks and 3D frameworks from phosphomolybdate clusters and binuclear Cu(ii) complexes. The syntheses and structures of [{Cu2(tpypyz)(H2O)2}(Mo5 O15)(HOPO3)2]·nH 2O [n = 2, 3; tpypyz = tetra(2-pyridyl)pyrazine]

The hydrothermal reaction of MoO3, Cu(C2H3O2)2.H2O, tpypyz, H3PO4 and H2O yields a 2D material, [(Cu2(tpypyz)(H2O)2)(Mo5O15)(HOPO3)2].2H2O (1.2H2O), constructed from (Mo5O15(HOPO3)2)4- clusters linked through (Cu2(tpypyz)(H2O)2)2+ components; in contrast, use of Cu2O in the synthesis in place of Cu(C2H3O2)2.H2O yields a 3D material [(Cu2(tpypyz)(H2O)2)(Mo5O15)(HOPO3)2].3H2O (2.3H2O), constructed from the same building blocks as 1.2H2O.

Nicotine effects on regional cerebral blood flow in awake, resting tobacco smokers

The hypothesis for this research was that regional cerebral blood flow (rCBF) would increase following nasal nicotine administration to overnight abstinent tobacco smokers in relationship to the known brain distribution of nicotinic cholinergic receptors (nAChRs). Nine male and nine female healthy adult smokers were studied. They abstained overnight from tobacco products for 10 or more hours prior to study the next morning. Nicotine nasal spray was given in doses of 1-2.5 mg total with half in each nostril while the subject was awake and resting in a supine position. Oleoresin of pepper solution in a similar volume was used as an active placebo to control for the irritating effects of nicotine. Both substances were given single blind to the subjects. Positron emission tomography (PET) with H(2)(15)O was used to measure rCBF. The data from each subject volunteer were normalized to global activity to better assess regional brain changes. Both nasal nicotine and pepper spray produced similar increases in CBF in somesthetic area II, consistent with the irritant effects of both substances. The mean rCBF effects of nasal pepper were subtracted from those of nasal nicotine to determine the actions of nicotine alone. The latter produced increases in rCBF in the thalamus, pons, Brodman area 17 of the visual cortex, and cerebellum. Some brain areas that contain a large number of nAChRs, such as the thalamus, showed an increase in CBF. Other areas that have few nAChRs, such as the cerebellum, also showed an increase in relative CBF. The hippocampal/parahippocampal areas showed greater regional decreases (left) and lesser increases (right) in CBF that correlated with the increase in plasma arterial nicotine concentrations. The results obtained indicate complex primary and secondary effects of nicotine in which only some regional brain CBF changes correlate with the known distribution of nAChR. No gender differences were noted.

In vivo measurement of the vesicular monoamine transporter in schizophrenia

Given evidence for excessive striatal dopamine activity in schizophrenia, we sought to test the hypothesis that dopaminergic innervation in the striatum is abnormally elevated, and a secondary hypothesis that age-related loss is accelerated. Twelve schizophrenic subjects on stable doses of medications, along with 12 age and sex-matched healthy control subjects, underwent positron emission tomography (PET) studies with [11C]dihydrotetrabenazine (DTBZ), which binds to the vesicular monoamine transporter, type 2 (VMAT2). DTBZ binding reflects principally dopaminergic projections in the striatum and appears in animal models, over treatment periods as long as two weeks, not to be regulated by antipsychotic drugs. Using an equilibrium analysis, we obtained measurements of the binding potential (BP) of [11C]DTBZ, as well as a transport (K(1)) measure, corresponding to regional cerebral blood flow. BP in the striatum showed no difference between the patient and control groups, and no differential effect of age. We did not find evidence supporting the hypothesis that excessive dopamine activity in schizophrenia could be explained by increased density of striatal dopamine terminals.

Solid-state coordination chemistry: influences of (M(terpyridyl))(M = Fe(III), Cu(II), Ni(II)) subunits on molybdenum oxide structures

The hydrothermal reactions of Na2MoO4 x 2H2O and 2,2':6',2"-terpyridine with appropriate salts of Fe(II), Cu(II), and Zn(II) yield a variety of mixed metal oxide phases. The Cu(II) system affords the molecular cluster [Cu(terpy)MoO4].3H2O (MOXI-40 x 3H2O), as well as a one-dimensional material [Cu(terpy)Mo2O7](MOXI-41) which is constructed from (Mo4O14)4- clusters linked through (Cu(terpy))2+ units. In constrast, the Zn(II) phase of stoichiometry identical to that of MOXI-41, [Zn(terpy)Mo2O7](MOXI-42), exhibits a one-dimensional structure characterized by a (Mo2O7)n2n- chain decorated with peripheral (Zn(terpy))2+ subunits. The iron species [(Fe(terpy))2Mo4O12](MOXI-43) is also one-dimensional but exhibits [(Fe(terpy))2(MoO4)2]2+ rings linked through (MoO4)2- tetrahedra. A persistent structural motif which appears in MOXI-40, MOXI-41, and MOXI-43 is the [(M(terpy))2(MoO4)2]n cluster with a cyclic )(M2Mo2O4) core. In general, the secondary metal sites M(II, III) are effective bridging groups between molybdate subunits of varying degrees of aggregation. Furthermore, the ligands passivate the bimetallic oxide from spatial extension in two or three dimensions and provide a routine entree into low-dimensional structural types of the molybdenum oxide family of materials.

High vesicular monoamine transporter binding in asymptomatic bipolar I disorder: sex differences and cognitive correlates

OBJECTIVE

It has been hypothesized that anomalies in monoaminergic function underlie some of the manifestations of bipolar disorder. In this study the authors examined the possibility that trait-related abnormalities in the concentration of monoaminergic synaptic terminals may be present in patients with asymptomatic bipolar disorder type I.

METHOD

The concentration of a stable presynaptic marker, the vesicular monoamine transporter protein (VMAT2), was quantified with (+)[(11)C]dihydrotetrabenazine (DTBZ) and positron emission tomography. Sixteen asymptomatic patients with bipolar I disorder who had a prior history of mania with psychosis (nine men and seven women) and individually matched healthy subjects were studied. Correlational analyses were conducted to examine the relationship between regional VMAT2 binding, cognitive function, and clinical variables.

RESULTS

VMAT2 binding in the thalamus and ventral brainstem of the bipolar patients was higher than that in the comparison subjects. VMAT2 concentrations in these regions correlated with performance on measures of frontal, executive function. In addition, sex differences in VMAT2 binding were detected in the thalamus of the bipolar patients; the male patients had higher binding than the women. No sex differences in binding were observed in the healthy comparison group.

CONCLUSIONS

These initial results suggest that higher than normal VMAT2 expression and, by extension, concentration of monoaminergic synaptic terminals, may represent a trait-related abnormality in patients with bipolar I disorder and that male and female patients show different patterns. Also, VMAT2 concentrations may be associated with some of the cognitive deficits encountered in euthymic bipolar disorder.

Ligand influences of the structures of molybdenum oxide networks

The influence of organonitrogen ligands on the network structure of molybdenum oxides was examined by preparing three new molybdenum oxide phases [MoO3(4,4'-bpy)0.5] (MOXI-8), [HxMoO3(4,4'-bpy)0.5] (MOXI-9), and [MoO3(triazole)0.5] (MOXI-32). The structure of [MoO3(4,4'-bpy)0.5) consists of layers of corner-sharing MoO5N octahedra, buttressed by bridging 4,4'-bipyridyl ligands into a three-dimensional covalently bonded organic-inorganic composite material. Partial reduction of [MoO3(4,4'-bpy)0.5] yields the mixed-valence material [HxMoO3(4,4'-bpy)0.5] (x approximately 0.5). The most apparent structural change upon reduction is found in the Mo-ligand bond lengths of the MoO5N octahedra, which exhibit the usual (2 + 2 + 2) pattern in [MoO3(4,4'-bpy)0.5] and a more regular (5 + 1) pattern in [HxMoO3(4,4'-bpy)0.5]. Substitution of triazole for 4,4'-bipyridine yields [MoO3(triazole)0.5], which retains the layer motif of corner-sharing MoO5N octahedra but with distinct sinusoidal ruffling in contrast to planar layers of [MoO3(4,4'-bpy)0.5] and [HxMoO3(4,4'-bpy)0.5]. The folding reflects the ligand constraints imposed by the triazole ligand that bridges adjacent Mo sites within a layer. MOXI-8, C5H4NMoO3: monoclinic P2(1)/c, a = 7.5727(6) A, b = 7.3675(7) A, c = 22.433(3) A, beta = 90.396(8) degrees, Z = 8. MOXI-9, C5H4.5NMoO3: monoclinic I2/m, a = 5.2644(4) A, b = 5.2642(4) A, c = 22.730(2) A, beta = 90.035(1) degrees, Z = 4. MOXI-32, C2H3N3Mo2O6: orthorhombic Pbcm, a = 3.9289(5) A, b = 13.850(2) A, c = 13.366(2) A, Z = 4.

Buprenorphine-induced changes in mu-opioid receptor availability in male heroin-dependent volunteers: a preliminary study

A principle of opioid pharmacotherapy is that high medication doses should occupy fractionally more opioid receptors that mediate heroin effects. In this preliminary study we examined in vivo mu opioid receptor (muOR) binding in three healthy opioid-dependent volunteers during maintenance on 2 and 16 mg sublingual buprenorphine (BUP) liquid, and after detoxification (0 mg) under double-blind, placebo-controlled conditions, and once in matched controls. Binding measures were obtained with the muOR-selective radioligand [11C]carfentanil (CFN) and PET 4 hrs after BUP administration. BUP induced dose-dependent reductions in muOR availability, 36-50% at 2 mg and 79-95% at 16 mg relative to placebo. Heroin abusers also had greater muOR binding potential in the inferofrontal cortex and anterior cingulate regions during placebo, compared to matched controls. Further studies are warranted to examine the relationship of muOR availability with BUP therapeutic actions, and the clinical implications of increased muOR binding during withdrawal.

Structural influences of organonitrogen ligands on vanadium oxide solids. Hydrothermal syntheses and structures of the terpyridine vanadates [V2O4(terpy)2]3[V10O28], [VO2(terpy)][V4O10], and [V9O22(terpy)3]

Hydrothermal reactions of the V2O5/2,2':6':2"-terpyridine/ZnO/H2O system under a variety of conditions yielded the organic-inorganic hybrid materials [V2O4(terpy)2]3[V10O28].2H2O (VOXI-10), [VO2(terpy)][V4O10] (VOXI-11), and [V9O22(terpy)3] (VOXI-12). The structure of VOXI-10 consists of discrete binuclear cations [V2O4(terpy)2]2+ and one-dimensional chains [V10O28]6-, constructed of cyclic [V4O12]4- clusters linked through (VO4) tetrahedra. In contrast, the structure of VOXI-11 exhibits discrete mononuclear cations [VO2(terpy)]1+ and a two-dimensional vanadium oxide network, [V4O10]1-. The structure of the oxide layer is constructed from ribbons of edge-sharing square pyramids; adjacent ribbons are connected through corner-sharing interactions into the two-dimensional architecture. VOXI-12 is also a network structure; however, in this case the terpy ligand is incorporated into the two-dimensional oxide network whose unique structure is constructed from cyclic [V6O18]6- clusters and linear (V3O5(terpy)3) moieties of corner-sharing vanadium octahedra. The rings form chains through corner-sharing linkages; adjacent chains are connected through the trinuclear units. Crystal data: VOXI-10, C90H70N18O42V16, triclinic P1, a = 12.2071(7) A, b = 13.8855(8) A, 16.9832(10) A, alpha = 69.584(1) degrees, beta = 71.204(1) degrees, gamma = 84.640(1) degrees, Z = 1; VOXI-11, C15H11N3O12V5, monoclinic, P2(1)/n, a = 7.7771(1) A, b = 10.3595(2) A, c = 25.715(4) A, beta = 92.286(1) degrees, Z = 4; VOXI-12, C45H33N9O22V9, monoclinic C2/c, a = 23.774(2) A, b = 9.4309(6) A, c = 25.380(2) A, beta = 112.047(1) degrees, Z = 4.

Effects of yohimbine on cerebral blood flow, symptoms, and physiological functions in humans

OBJECTIVE

Increases in adrenergic activity are associated with stress, anxiety, and other psychiatric, neurological, and medical disorders. To improve understanding of normal CNS adrenergic function, CBF responses to adrenergic stimulation were determined.

METHODS

Using PET, the CBF changes after intravenous yohimbine, an alpha2-adrenoreceptor antagonist that produces adrenergic activation, were compared with placebo in nine healthy humans. Heart rate, blood pressure, Paco2, plasma catecholamines, and symptom responses were also determined.

RESULTS

Among nonscan variables, yohimbine produced significant symptom increases (including a panic attack in one subject), a decrease in Paco2 due to hyperventilation, increases in systolic and diastolic blood pressure, and a trend toward a significant norepinephrine increase. Among scan results, yohimbine produced a significant decrease in whole-brain absolute CBF; regional decreases were greatest in cortical areas. Medial frontal cortex, thalamus, insular cortex, and cerebellum showed significant increases after normalization to whole brain. Medial frontal CBF change was correlated with increases in anxiety. A panic attack produced an increase instead of a decrease in whole-brain CBF. Factors potentially contributing to the observed CBF changes were critically reviewed. Specific regional increases were most likely due in large part to activation produced by adrenergically induced anxiety and visceral symptoms.

CONCLUSIONS

This study supports the relationship of anxiety and interoceptive processes with medial frontal, insular, and thalamic activation and provides a baseline for comparison of normal yohimbine-induced CNS adrenergic activation, adrenergically-based symptoms, and other markers of adrenergic function to stress, emotion, and the adrenergic pathophysiologies of various CNS-related disorders.

Solid-State Coordination Chemistry: The Self-Assembly of Microporous Organic-Inorganic Hybrid Frameworks Constructed from Tetrapyridylporphyrin and Bimetallic Oxide Chains or Oxide Clusters

The hydrothermal reactions of MoO(3), tetrapyridylporphyrin (tpypor), water, and the appropriate M(II) precursor yield the first examples of three-dimensional framework materials constructed from metal oxide and porphyrin subunits. The picture shows a section of [{Fe(tpypor)}(3)Fe(Mo(6)O(19))(2)] small middle dotx H(2)O with the [Fe(8)(tpypor)(6)](8+) building block of the cationic framework and the entrained {Mo(6)O(19)}(2-) cluster.

Arterial/venous plasma nicotine concentrations following nicotine nasal spray

BACKGROUND AND OBJECTIVES

Arterial (A) and venous (V) plasma nicotine and cotinine concentrations were measured after nasal nicotine spray in tobacco smokers of both genders. The hypothesis for this research was that a greater A/V difference in plasma nicotine would be present in males than females because males have greater skeletal muscle mass to bind nicotine.

SUBJECTS AND METHODS

Nine male and nine female healthy adult smokers were studied. They all abstained from use of tobacco overnight for 10 h or more prior to the study. Nicotine nasal spray was given in doses of 1-2.5 mg total, with half in each nostril while the subject was supine. Both A and V blood samples were obtained prior to and 3, 6, 10, 15, 20, and 30 min post-nasal nicotine spray.

RESULTS AND CONCLUSIONS

Nasal nicotine administration produced greater A than V plasma levels. There were no gender differences in A/V nicotine concentrations, disproving the above hypothesis, suggesting that other physiochemical factors besides skeletal muscle mass must be involved. Heart rate increases correlated well with arterial plasma nicotine levels (r = 0.77). Males had less variance than females in the expected increase in arterial plasma nicotine concentrations with increased number of nasal sprays. Although there was considerable overlap, mean A cotinine concentrations were consistently slightly larger than V concentrations.

Quantification of delta-opioid receptors in human brain with N1'-([11C]methyl) naltrindole and positron emission tomography

The regional binding of N1'-([11C]methyl)naltrindole (MeNTI), a selective delta-opioid antagonist, was studied in healthy human subjects with positron emission tomography (PET). After the bolus intravenous administration of high specific activity [11C]MeNTI, PET was performed over 90 minutes. Arterial plasma samples were obtained during the scanning period and assayed for the presence of radiolabeled metabolites. The data were analyzed with various kinetic (two- and three-compartment models, Patlak graphical analysis) and nonkinetic (apparent volume of distribution and activity at a late scanning time) approaches. This tracer showed irreversible binding characteristics during the scanning period used. The results of the analyses also were compared with the density and distribution of delta-opioid receptors in the human brain in vitro. Additionally, computer simulations were performed to assess the effects of changes in receptor binding and tracer transport changes on the perceived binding parameters obtained with the models. A constrained three-compartment kinetic model was demonstrated to be superior to other quantification models for the description of MeNTI kinetics and quantification of delta receptor binding in the human brain with 11C-labeled MeNTI.

Organic-Inorganic Hybrid Materials: From "Simple" Coordination Polymers to Organodiamine-Templated Molybdenum Oxides

A blueprint for the design of oxide materials is provided by nature. By borrowing from nature's ability to influence inorganic microstructures in biomineralization processes and in the hydrothermal synthesis of complex minerals, a new class of materials in which organic components exert a role in controlling inorganic microstructure is evolving. By employing members of the ever-expanding class of polymeric coordination complex cations, novel molybdenum oxide substructures, such as the one shown, may be prepared.

Gender and age influences on human brain mu-opioid receptor binding measured by PET

OBJECTIVE

Both age and gender are being increasingly recognized as important factors influencing CNS structure and function. However, there are relatively few data on actual neurochemical differences between the sexes in human subjects or on their interaction with age. One of the central neurotransmitter systems for which sex differences have been suggested by animal models and clinical human data is the opioid. In this study the authors examined age- and gender-associated variations in mu-opioid receptor binding with positron emission tomography (PET).

METHOD

Healthy human subjects were studied with PET and the radiotracer [11C]carfentanil, a selective mu-opioid agonist. Two separate subject groups were examined: one group of 24 men and 12 women was studied in a retrospective analysis of data, and a second group of 12 men and 18 women was recruited prospectively and studied with a higher-resolution scanner.

RESULTS

Mu-opioid receptor binding potential (Bmax/Kd) was found to increase with age in neocortical areas and the putamen. Sex differences, with higher mu-opioid binding in women, were observed in a number of cortical and subcortical areas. Gender-by-age interactions were observed in the thalamus and the amygdala; in vivo mu-opioid binding declined in postmenopausal women to levels below those of men.

CONCLUSIONS

These data imply that both age and gender are important variables to consider in the interpretation of investigations of human function in which the opioid system plays a role. Also, women's reproductive status (reproductive age versus postmenopausal) may influence the function of CNS opioid systems.

Medial frontal cortex involvement in PTSD symptoms: a SPECT study

The regional cerebral blood flow (rCBF) responses to a combat stress-related auditory stimulus was examined in Vietnam veterans diagnosed with posttraumatic stress disorder (PTSD). Based on prior data in healthy subjects, we hypothesized that the medial prefrontal cortex may be involved in the processing of stress responses. Twelve male veterans diagnosed with PTSD, 11 age-matched, combat-exposed subjects without PTSD, and 12 healthy control subjects were studied with single-photon emission tomography and the blood flow tracer [99mTc]-HMPAO. Subjects were studied twice, while listening to combat sounds or white noise. Significant increases in the blood flow to the medial prefrontal cortex were observed in PTSD patients, but not in the control groups, which correlated at trend levels with psychophysical measures of stress response. These data support the involvement of the medial prefrontal cortex in the pathophysiology of PTSD, possibly mediating some of its symptoms.

PET imaging of the dopamine transporter in progressive supranuclear palsy and Parkinson's disease

OBJECTIVE

To differentiate the patterns of dopamine transporter loss between idiopathic PD and progressive supranuclear palsy (PSP).

METHODS

We used the radiotracer [11C]-WIN 35,428 and PET. Regional striatal dopamine transporter binding was measured in the caudate, anterior putamen, and posterior putamen of six patients with L-dopa-responsive stage 2 PD, six patients with PSP, and six age-comparable healthy controls.

RESULTS

In patients with idiopathic PD, the most marked abnormality was observed in the posterior putamen (77% reduction), whereas transporter density in the anterior putamen (60% reduction) and the caudate (44% reduction) was less affected. Unlike the patients with PD, the PSP group showed a relatively uniform degree of involvement in the caudate (40% reduction), anterior putamen (47% reduction), and posterior putamen (51% reduction). When posterior putamen/caudate ratios were calculated, these values were significantly lower in patients with PD than they were in patients with PSP (p = 0.0008) and the control group (p < 0.0001).

CONCLUSIONS

Patients with PD have a more pronounced loss of dopamine transporters in the posterior putamen due to a subdivisional involvement of nigrostriatal dopaminergic projections in idiopathic PD. This technique is useful in the determination of neurochemical changes underlying PD and PSP, thus differentiating between them.

Two year follow-up of atypical depression

The symptom cluster of Atypical Depression (AD) has been characterized based on its presentation and selective response to pharmcological treatments, while relatively little is known about the outcome of these patients after treatment trials. The present study was undertaken to assess the long term outcome of 40 patients after a controlled treatment trial of fluoxetine vs phenelzine. Twenty five of these subjects were interviewed approximately two years after completion of the initial trial. They reported a high frequency of symptom recurrence, but generally little symptomatic or social impairment between episodes. Eighteen subjects were taking antidepressants at follow-up. A higher frequency of depressive episodes was recorded during the times when off antidepressant medications. Overall outcome was rated as moderate or good in the majority of subjects. These results suggest that AD presents from similarities with other subtypes of depression, with high rates of symptomatic recurrence and lasting response to chronic antidepressant treatment. Conversely, social functioning and overall outcome appear more favorable in AD.

Brain opioid receptor measurements by positron emission tomography in normal cycling women: relationship to luteinizing hormone pulsatility and gonadal steroid hormones

The regulation of central mu-opioid receptors in women during the menstrual cycle was explored with positron emission tomography and the selective radiotracer [11C]carfentanil. Ten healthy women were studied twice, during their follicular and luteal phases. Plasma concentrations of estradiol, progesterone, testosterone, and beta-endorphin were determined immediately before scanning. LH pulsatility was measured over the 9 h preceding each of the two positron emission tomography scans. No significant differences in the binding potential of mu-opioid receptors (binding capacity/Kd) were observed between phases of the menstrual cycle. However, significant negative correlations were observed between circulating levels of estradiol during the follicular phase and mu-receptor binding measures in the amygdala and hypothalamus, two regions thought to be involved in the regulation of GnRH pulsatility. LH pulse amplitude was positively correlated with mu binding in the amygdala, whereas LH pulse number was negatively correlated with binding in this same region. No significant associations were noted between LH pulse measures and the hypothalamus for this sample. These results suggest that amygdalar mu-opioid receptors exert a modulatory effect on GnRH pulsatility, and that circulating levels of estradiol also regulate central mu-opioid function.

Quantification of muscarinic cholinergic receptors with [11C]NMPB and positron emission tomography: method development and differentiation of tracer delivery from receptor binding

Quantification of human brain muscarinic cholinergic receptors was investigated with the use of [11C]N-methyl-4-piperidyl benzylate (NMPB) and positron emission tomography (PET). Whole-brain uptake of NMPB at 90 to 110 minutes after intravenous injection was approximately 10% of the administered dose. The initial cerebral distribution of NMPB corresponded to the pattern of cerebral perfusion; however, at progressively longer postinjection intervals, regional distinctions consistent with muscarinic receptor binding were evident: activity at 90 to 110 minutes postinjection was highest in the striatum and cerebral cortex, intermediate in the thalamus and pons, and lowest in the cerebellum. After the development of a chromatographic system for isolation of authentic [11C]NMPB in plasma, tracer kinetic modeling was used to estimate receptor binding from the cerebral and arterial plasma tracer time-courses. Ligand transport rate and receptor-binding estimates were obtained with the use of compartmental models and analytical methods of varying complexity, including a two-parameter pixel-by-pixel-weighted integral approach and regional least-squares curve-fitting analyses employing both two- and three-compartment model configurations. In test-retest experiments, precision of the methods and their abilities to distinguish altered ligand delivery from binding in occipital cortex during an audiovisual presentation were evaluated. Visual stimulation increased the occipital blood-to-brain NMPB transport rate by 25% to 46% in estimates arising from the various approaches. Weighted integral analyses resulted in lowest apparent transport changes and in a concomitant trend toward apparent binding increases during visual activation. The regional least-squares procedures were superior to the pixel-by-pixel method in isolating the effects of altered tracer delivery from receptor-binding estimates, indicating larger transport effects and unaltered binding. Precision was best (less than 10% test-retest differences) for the weighted integral analyses and was somewhat lower in the least-squares analyses (10-25% differences). The authors conclude that pixel-by-pixel-weighted integral analyses of NMPB distribution introduce transport biases into receptor-binding estimates. Similar confounding effects also are predicted in noncompartmental analyses of delayed radiotracer distribution. The use of regional nonlinear least-squares fitting to two- and three-compartment models, although more labor intensive, provides accurate distinction of receptor-binding estimates from tracer delivery with acceptable precision in both intra- and intersubject comparisons.

Imaging of delta- and mu-opioid receptors in temporal lobe epilepsy by positron emission tomography

The involvement of opioid neurotransmitter systems in seizure mechanisms is well documented. In previous positron emission tomography (PET) studies in patients with unilateral temporal lobe epilepsy, we have found evidence for differential regulation of the opioid-receptor subtypes. The present study extends our previous observations to delta-opioid receptors by using the delta-receptor-selective antagonist [11C]methylnaltrindole ([11C]MeNTI). Paired measurements of delta- and mu-opioid receptor binding and metabolic activity were performed with PET using [11C]MeNTI and [11C]carfentanil ([11C]CFN) and [18F]fluorodeoxyglucose ([18F]FDG), respectively. Binding of [11C]MeNTI and [11C]CFN increased and [18F]FDG uptake decreased in the temporal cortex (TC) ipsilateral to the focus. Decreases in [18F]FDG uptake were more widespread regionally than were increases in opioid receptors. Increases in the delta- and mu-receptor binding showed different regional patterns. Increases in mu-receptor binding were confined to the middle aspect of the inferior TC, whereas binding of delta receptors increased in the mid-inferior TC and anterior aspect of the middle and superior TC. The increase in delta receptors suggests their anticonvulsant action, as previously shown for the delta-receptor subtype, whereas the different regional pattern of receptor alterations suggest the distinct roles of different opioid-receptor subtypes in seizure phenomena.