1
|
Gallagher CL, Christian BT, Holden JE, Dejesus OT, Nickles RJ, Buyan-Dent L, Bendlin BB, Harding SJ, Stone CK, Mueller B, Johnson SC. A within-subject comparison of 6-[18F]fluoro-m-tyrosine and 6-[18F]fluoro-L-dopa in Parkinson's disease. Mov Disord 2011; 26:2032-8. [PMID: 21638324 DOI: 10.1002/mds.23778] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 03/10/2011] [Accepted: 04/11/2011] [Indexed: 11/12/2022] Open
Abstract
Progression of Parkinson's disease symptoms is imperfectly correlated with positron emission tomography biomarkers for dopamine biosynthetic pathways. The radiopharmaceutical 6-[(18) F]fluoro-m-tyrosine is not a substrate for catechol-O-methyltransferase and therefore has a more favorable uptake-to-background ratio than 6-[(18) F]fluoro-L-dopa. The objective of this study was to evaluate 6-[(18) F]fluoro-m-tyrosine relative to 6-[(18) F]fluoro-L-dopa with partial catechol-O-methyltransferase inhibition as a biomarker for clinical status in Parkinson's disease. Twelve patients with early-stage Parkinson's disease, off medication, underwent Unified Parkinson Disease Rating Scale scoring, brain magnetic resonance imaging, and 3-dimensional dynamic positron emission tomography using equivalent doses of 6-[(18) F]fluoro-m-tyrosine and 6-[(18) F]fluoro-L-dopa with tolcapone, a catechol-O-methyltransferase inhibitor. Images were realigned within subject, after which the tissue-derived uptake rate constant was generated for volumes of interest encompassing the caudate nucleus, putamen, and subregions of the putamen. We computed both bivariate (Pearson) and partial (covariate of age) correlations between clinical subscores and tissue-derived uptake rate constant. Tissue-derived uptake rate constant values were correlated between the radiopharmaceuticals (r = 0.8). Motor subscores were inversely correlated with the contralateral putamen 6-[(18) F]fluoro-m-tyrosine tissue-derived uptake rate constant (|r| > 0.72, P < .005) but not significantly with the 6-[(18) F]fluoro-L-dopa tissue-derived uptake rate constant. The uptake rate constants for both radiopharmaceuticals were also inversely correlated with activities of daily living subscores, but the magnitude of correlation coefficients was greater for 6-[(18) F]fluoro-m-tyrosine. In this design, 6-[(18) F]fluoro-m-tyrosine uptake better reflected clinical status than did 6-[(18) F]fluoro-L-dopa uptake. We attribute this finding to 6-[(18) F]fluoro-m-tyrosine's higher affinity for the target, L-aromatic amino acid decarboxylase, and the absence of other major determinants of the uptake rate constant. These results also imply that L-aromatic amino acid decarboxylase activity is a major determinant of clinical status.
Collapse
|
2
|
Asari S, Fujimoto KI, Miyauchi A, Sato T, Nakano I, Muramatsu SI. Subregional 6-[18F]fluoro-ʟ-m-tyrosine uptake in the striatum in Parkinson's disease. BMC Neurol 2011; 11:35. [PMID: 21429212 PMCID: PMC3078094 DOI: 10.1186/1471-2377-11-35] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 03/23/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In idiopathic Parkinson's disease (PD) the clinical features are heterogeneous and include different predominant symptoms. The aim of the present study was to determine the relationship between subregional aromatic l-amino acid decarboxylase (AADC) activity in the striatum and the cardinal motor symptoms of PD using high-resolution positron emission tomography (PET) with an AADC tracer, 6-[18F]fluoro-ʟ-m-tyrosine (FMT). METHODS We assessed 101 patients with PD and 19 healthy volunteers. PD was diagnosed based on the UK Brain Bank criteria by two experts on movement disorders. Motor symptoms were measured with the Unified Parkinson's Disease Rating Scale (UPDRS). FMT uptake in the subregions of the striatum was analyzed using semi-automated software for region-of-interest demarcation on co-registered magnetic resonance images. RESULTS In all PD patients, FMT uptake was decreased in the posterior putamen regardless of predominant motor symptoms and disease duration. Smaller uptake values were found in the putamen contralateral to the side with more affected limbs. The severity of bradykinesia, rigidity, and axial symptoms was correlated with the decrease of FMT uptake in the putamen, particularly in the anterior part. No significant correlation was observed between tremors and FMT uptake. CONCLUSIONS Decrease of FMT uptake in the posterior putamen appears to be most sensitive in mild PD and uptake in the anterior putamen may reflect the severity of main motor symptoms, except for tremor.
Collapse
Affiliation(s)
- Sayaka Asari
- Division of Neurology, Department of Medicine, Jichi Medical University, Tochigi, Japan.
| | | | | | | | | | | |
Collapse
|
3
|
Bergmann R, Pietzsch J. Small animal positron emission tomography in food sciences. Amino Acids 2005; 29:355-76. [PMID: 16142524 DOI: 10.1007/s00726-005-0237-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Accepted: 07/13/2005] [Indexed: 02/07/2023]
Abstract
Positron emission tomography (PET) is a 3-dimensional imaging technique that has undergone tremendous developments during the last decade. Non-invasive tracing of molecular pathways in vivo is the key capability of PET. It has become an important tool in the diagnosis of human diseases as well as in biomedical and pharmaceutical research. In contrast to other imaging modalities, radiotracer concentrations can be determined quantitatively. By application of appropriate tracer kinetic models, the rate constants of numerous different biological processes can be determined. Rapid progress in PET radiochemistry has significantly increased the number of biologically important molecules labelled with PET nuclides to target a broader range of physiologic, metabolic, and molecular pathways. Progress in PET physics and technology strongly contributed to better scanners and image processing. In this context, dedicated high resolution scanners for dynamic PET studies in small laboratory animals are now available. These developments represent the driving force for the expansion of PET methodology into new areas of life sciences including food sciences. Small animal PET has a high potential to depict physiologic processes like absorption, distribution, metabolism, elimination and interactions of biologically significant substances, including nutrients, 'nutriceuticals', functional food ingredients, and foodborne toxicants. Based on present data, potential applications of small animal PET in food sciences are discussed.
Collapse
Affiliation(s)
- R Bergmann
- Positron Emission Tomography Center, Institute of Bioinorganic and Radiopharmaceutical Chemistry, Research Center Rossendorf, Dresden, Germany.
| | | |
Collapse
|
4
|
|
5
|
Dejesus OT, Endres CJ, Shelton SE, Nickles RJ, Holden JE. Noninvasive assessment of aromatic L-amino acid decarboxylase activity in aging rhesus monkey brain in vivo. Synapse 2001; 39:58-63. [PMID: 11071710 DOI: 10.1002/1098-2396(20010101)39:1<58::aid-syn8>3.0.co;2-b] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effect of aging on aromatic L-amino acid decarboxylase (AAAD) activity in rhesus monkey striatum was assessed in vivo using PET imaging. Two analogs of L-DOPA, 6-fluoro-m-tyrosine (FMT) and 6-fluoro-L-DOPA (FDOPA), were used to image rhesus monkeys of various ages. Results show that when the animals were grouped between young (3-11 years) and aged (25-37 years), FDOPA uptake in the older animals showed a 21% decline (P < 0.0005), while FMT uptake in young and older animals were not different. On the other hand, when individual uptake values were plotted vs. age, linear regression analysis showed FDOPA uptake similarly declined with age (r = -0.84, P < 0.001) while FMT uptake increased with age (r = 0.66, P < 0.05). Since FMT pharmacokinetics has been shown to be unaffected by metabolic steps occurring after the AAAD step, while FDOPA traces all the steps involved in L-DOPA metabolism, FMT is a suitable tracer to assess AAAD activity while FDOPA traces dopamine turnover. Based on these tracer characteristics, this study found that AAAD activity is maintained or increased in the aging rhesus monkey striatum while the FDOPA uptake decreases with age consistent with age-related declines in neuronal mechanisms whose overall effect is increased striatal dopamine turnover and clearance. Furthermore, comparison of results of this study with previous studies support the notion that the effect of aging in the dopamine system is different from that of MPTP-induced parkinsonism.
Collapse
Affiliation(s)
- O T Dejesus
- Department of Medical Physics, University of Wisconsin Medical School Madison, Wisconsin 53706, USA.
| | | | | | | | | |
Collapse
|
6
|
Stein TD, DeJesus OT. Effect of 6-fluoro-m-tyrosine on dopamine release and metabolism in rat striatum using in vivo microdialysis. Brain Res 2000; 884:192-5. [PMID: 11082501 DOI: 10.1016/s0006-8993(00)02976-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
6-[(18)F]Fluoro-m-tyrosine (FMT) is a positron emission tomography (PET) imaging agent for the aromatic L-amino acid decarboxylase enzyme. Its parent compound, L-m-tyrosine (LMT) induces behavioral effects in rodents via dopamine release. To assess the potential pharmacologic effect of FMT, its role in dopamine release and metabolism in rat striatum was compared with LMT and L-DOPA using in vivo microdialysis. Results indicate that FMT will not have the same dopamine-induced behavioral effects as LMT.
Collapse
Affiliation(s)
- T D Stein
- Department of Medical Physics, University of Wisconsin Medical School, 1530 Medical Sciences Center, 1300 University Avenue, Madison, WI 53706, USA
| | | |
Collapse
|
7
|
Brown WD, DeJesus OT, Pyzalski RW, Malischke L, Roberts AD, Shelton SE, Uno H, Houser WD, Nickles RJ, Holden JE. Localization of trapping of 6-[(18)F]fluoro-L-m-tyrosine, an aromatic L-amino acid decarboxylase tracer for PET. Synapse 1999; 34:111-23. [PMID: 10502310 DOI: 10.1002/(sici)1098-2396(199911)34:2<111::aid-syn4>3.0.co;2-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The purpose of this study was to address four major questions regarding 6-FMT, a noncatecholic PET tracer for AAAD: 1) Where is the specific uptake of 6-FMT? 2) Why does it accumulate where and to the degree that it does? 3) How does its uptake differ from that of fluoroDOPA globally? and 4) Does its regional uptake differ significantly from that of fluoroDOPA? High-resolution PET scans were obtained in three rhesus monkeys using 6-FMT and in two of them using fluoroDOPA. Anatomic distribution was analyzed visually and quantitative uptake of 6-FMT was compared with published regional decarboxylase activity and monoamine neurotransmitter concentrations. In addition to high uptake in the dopamine-rich striatal nuclei, there was specific uptake of 6-FMT in brain regions which have little dopaminergic innervation but which have other amines in significant concentration. 6-FMT uptake correlated best with regional AAAD activity (r = 0.97). It correlated slightly less well with the sum of catecholamine and indolamine neurotransmitter concentrations, but does not correlate with dopamine concentration. The uptake of 6-FMT is greater than that of fluoroDOPA, with only slight differences in their regional distributions. Radiolabeled analogs of DOPA are often implicitly or explicitly regarded as tracers for presynaptic dopaminergic function. However, localization of these tracers more broadly includes many regions with relatively high concentrations of norepinephrine and serotonin. This may be especially important in diseases or experimental states in which dopaminergic neurons are selectively reduced, and may allow for the study of nondopaminergic neuronal systems in vivo with this tracer.
Collapse
Affiliation(s)
- W D Brown
- Department of Radiology, University of Wisconsin-Madison, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Lacan G, Satyamurthy N, Barrio JR. Synthesis of stereo (R and S) and geometric (E and Z) isomers of [18F]fluoro-beta-fluoromethylene-m-tyrosine derivatives: in vivo probes of central dopaminergic function. Nucl Med Biol 1999; 26:359-63. [PMID: 10382837 DOI: 10.1016/s0969-8051(99)00006-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Fluorination of pure R and S enantiomers of (E)-beta-fluoromethylene-m-tyrosine [(E)-FMMT] and its racemic geometric isomer, (Z)-beta-fluoromethylene-m-tyrosine [(Z)-FMMT] with [18F]acetyl hypofluorite ([18F]AcOF) gave a mixture of aromatic ring fluorinated products and a pair of diastereomeric products of addition across the exocyclic double bond. Semipreparative high performance liquid chromatography (HPLC) enabled a complete separation and isolation of these products, namely, 6-[18F]fluoro, 2-[18F]fluoro, and 2,6-[18F]difluoro (E)-FMMT and (Z)-FMMT derivatives. No attempt was made to isolate the individual components of the addition product. Pure racemic 4-[18F]fluoro-(E)-beta-fluoromethylene-m-tyrosine was also synthesized from a substituted (E)-FMMT precursor involving a fluorodestannylation reaction with [18F]F2. The availability of stereo (R and S) isomers of 6-[18F]fluoro and 2-[18F]fluoro (E)-FMMT and those of the racemic (Z)-FMMT along with 4-[18F]fluoro-(E)-beta-fluoromethylene-m-tyrosine would now enable a systematic investigation of the central monoamine oxidase/aromatic amino acid decarboxylase enzyme system with positron emission tomography.
Collapse
Affiliation(s)
- G Lacan
- Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, California 90095, USA
| | | | | |
Collapse
|
9
|
Huang SC, Quintana J, Satyamurthy N, Lacan G, Yu DC, Phelps ME, Barrio JR. [18F]Fluoro-beta-fluoromethylene-m-tyrosine derivatives show stereo, geometrical, and regio specificities as in vivo central dopaminergic probes in monkeys. Nucl Med Biol 1999; 26:365-70. [PMID: 10382838 DOI: 10.1016/s0969-8051(99)00008-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Stereo (D and L), geometrical (E and Z), and regiospecific (2-, 4-, and 6-[18F]fluoro) analogs of beta-fluoromethylene-m-tyrosine (FMMT) have been investigated in adult vervet monkeys (Cercopithecus aethiops sabaeus, n = 12) in vivo with positron emission tomography (PET). Brain transport through the blood-brain barrier and central aromatic amino acid decarboxylase (AAAD)-mediated decarboxylation rates were established. Results show strict structural dependency of the kinetic behavior of radiofluorinated FMMT analogs, with the E-isomer exhibiting a higher specificity over the (Z) geometrical counterpart for central dopaminergic structures. The 6-[18F]fluoro substituted L-(E)-FMMT was also favored over the 2- and 4-[18F]fluorosubstituted isomers in terms of their ability to localize in the same brain areas. The role of PET in drug development is also exemplified in this work.
Collapse
Affiliation(s)
- S C Huang
- Department of Molecular and Medical Pharmacology, UCLA School of Medicine, Los Angeles, California 90095, USA
| | | | | | | | | | | | | |
Collapse
|
10
|
Abstract
The trapping of decarboxylation products of radiolabelled dopa analogs in living human brain occurs as a function of the activity of dopa decarboxylase. This enzyme is now understood to regulate, with tyrosine hydroxylase, cerebral dopamine synthesis. Influx into brain of dopa decarboxylase substrates such as 6-[18F]fluorodopa and beta-[11C]dopa measured by positron emission tomography can be analyzed by solution of linear differential equations, assuming irreversible trapping of the decarboxylated products in brain. The isolation of specific physiological steps in the pathway for catecholamine synthesis requires compartmental modelling of the observed dynamic time-activity curves in plasma and in brain. The several approaches to the compartmental modelling of the kinetics of labelled substrates of dopa decarboxylase are now systematically and critically reviewed. Labelled catechols are extensively metabolized by hepatic catechol-O-methyltransferase yielding brain-penetrating metabolites. The assumption of a fixed blood-brain permeability ratio for O-methyl-6-[18F]fluorodopa or O-methyl-beta-[11C]dopa to the parent compounds eliminates several parameters from compartmental models. However, catechol-O-methyltransferase activity within brain remains a possible factor in underestimation of cerebral dopa decarboxylase activity. The O-methylation of labelled catechols is blocked with specific enzyme inhibitors, but dopa decarboxylase substrates derived from m-tyrosine may supplant the catechol tracers. The elimination from brain of decarboxylated tracer metabolites can be neglected without great prejudice to the estimation of dopa decarboxylase activity when tracer circulation is less than 60 minutes. However, elimination of dopamine metabolites from brain occurs at a rate close to that observed previously for metabolites of glucose labelled in the 6-position. This phenomenon can cause systematic underestimation of the rate of dopa decarboxylation in brain. The spillover of radioactivity due to the limited spatial resolution of tomographs also results in underestimation of dopa decarboxylase activity, but correction for partial volume effects is now possible. Estimates of dopa decarboxylase activity in human brain are increased several-fold by this correction. Abnormally low influx of dopa decarboxylase tracers in the basal ganglia is characteristic of Parkinson's disease and other movement disorders. Consistent with postmortem results, the impaired retention of labelled dopa is more pronounced in the putamen than in the caudate nucleus of patients with Parkinson's disease; this heterogeneity persists after correction for spillover. Current in vivo assays of dopa decarboxylase activity fail to discriminate clinically distinct stages in the progression of Parkinson's disease and are, by themselves, insufficient for differential diagnosis of Parkinson's disease and other subcortical movement disorders. However, potential new avenues for therapeutics can be tested by quantifying the rate of metabolism of exogenous dopa in living human brain.
Collapse
Affiliation(s)
- P Cumming
- McConnell Brain Imaging Centre, Montreal Neurological Institute, PQ Canada.
| | | |
Collapse
|
11
|
Ding YS, Gatley SJ, Fowler JS, Chen R, Volkow ND, Logan J, Shea CE, Sugano Y, Koomen J. Mapping catechol-O-methyltransferase in vivo: initial studies with [18F]Ro41-0960. Life Sci 1998; 58:195-208. [PMID: 9499160 DOI: 10.1016/0024-3205(95)02277-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ro41-0960 is a potent, fluorine containing COMT inhibitor which has be en reported to cross the blood brain barrier and to inhibit COMT in the brain. It is structurally similar to Ro40-7592 which is currently undergoing clinical trials in Parkinson's disease. Positron emission tomographic (PET) studies in baboon using F-18 labeled Ro41-0960 demonstrated a negligible uptake in the brain both at tracer doses and with the addition of unlabeled drug (1.5 mg/kg) at all times through a 90 min experimental interval. The brain to plasma ratios of F-18 averaged about 0.025. Region of interest analysis of the brain tissue area suggests that most of F-18 in the brain was due to the blood in the brain and not the brain tissue itself. However, high uptake was observed in the kidneys and in other organs which are known to have high COMT activity. Studies in mice showed that at 30 min after injection of tracer, F-18 in kidneys was largely as unchanged [18F]Ro41-0960 and that it could be displaced with unlabeled Ro41-0960. The fact that the average brain to blood ratio for mice (n=12) was 0.04, and that similar HPLC metabolite patterns were observed for brain and blood, provides consistent evidence that nearly all the F-18 in the brain represents F-18 in the cerebral blood vessels. These studies raise the question of whether the central pharmacological effects of Ro41-0960 are due to its presence in the brain. They also provide the first example of a positron emitter labeled radiotracer for COMT, and provide initial encouraging evidence that [18F]Ro41-0960 may be used to examine COMT in peripheral organs in vivo.
Collapse
Affiliation(s)
- Y S Ding
- Chemistry Dept., Brookhaven National Laboratory, Upton, NY, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Cumming P, Deep P, Rousset O, Evans A, Gjedde A. On the rate of decarboxylation of dopa to dopamine in living mammalian brain. Ann N Y Acad Sci 1997; 835:274-308. [PMID: 9616781 DOI: 10.1111/j.1749-6632.1997.tb48637.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- P Cumming
- McConnell Brain Imaging Centre, Montreal Neurological Institute, PQ, Canada
| | | | | | | | | |
Collapse
|
13
|
Endres CJ, Swaminathan S, DeJesus OT, Sievert M, Ruoho AE, Murali D, Rommelfanger SG, Holden JE. Affinities of dopamine analogs for monoamine granular and plasma membrane transporters: implications for PET dopamine studies. Life Sci 1997; 60:2399-406. [PMID: 9199484 DOI: 10.1016/s0024-3205(97)00300-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Affinities of dopamine (DA) analogs to both granular and plasma membrane uptake transporters were measured in vitro by inhibition of [3H]DA uptake in bovine chromaffin granule ghosts and C6 glial cells transfected with cDNA for the rat presynaptic dopamine transporter, respectively. Five amines were studied: DA, 6-fluorodopamine (6FDA), m-tyramine (MTA), 6-fluoro-m-tyramine (6FMTA), and beta-fluoromethylene-m-tyramine (FMMTA). Direct uptake of 18F labeled 6FDA and 6FMTA was also measured in the chromaffin granule system and compared with [3H]DA uptake. Results show that the transporter affinities of 6FDA and MTA were similar to that of DA in both transport systems while affinities of 6FMTA and FMMTA were lower. Furthermore while the direct uptake of DA and FDA in chromaffin granules were essentially identical and significantly reserpine-inhibitable, the direct uptake of 6FMTA was about 15-fold less and only minimally sensitive to reserpine pretreatment. Thus, although vesicular protection and reuptake may influence the turnover of FDA in 6-fluoroDOPA studies, they are unlikely to be important determinants of the kinetics of the slowly clearing components in studies with either 6-fluoro-m-tyrosine (6FMT) or 6-fluoro-beta-fluoro-methylene-m-tyrosine (6FFMMT), the bioprecursors of 6FMTA and 6-fluoro-FMMTA, respectively. These results are consistent with the finding that the longterm component in 6FMT PET studies is 6-fluoro-hydroxyphenylacetic acid (6FHPAC), which can be explained by the lack of vesicular protection of 6FMTA from MAO oxidation.
Collapse
Affiliation(s)
- C J Endres
- Department of Medical Physics, University of Wisconsin Medical School, Madison 53706, USA
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Hayase N, Tomiyoshi K, Watanabe K, Horikoshi S, Shibasaki T, Ohye C. Positron emission tomography with 4-[18F]fluoro-L-m-tyrosine in MPTP-induced hemiparkinsonian monkeys. Ann Nucl Med 1995; 9:119-23. [PMID: 8534583 DOI: 10.1007/bf03165037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
PET imaging studies with 4-[18F]fluoro-L-m-tyrosine (FMT) in normal macaca monkeys showed selective accumulations of radioactivity in the striatum with time. In monkeys rendered hemiparkinsonian by intracarotid infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), FMT uptake was eliminated in the lesioned striatum. FMT-PET studies were able to detect dopaminergic terminals in both normal and hemiparkinsonian monkeys, and clearly showed a reduction in aromatic L-amino acid decarboxylase (AAAD) activities in the MPTP-lesioned striatum. These results show that FMT is promising as a PET tracer for the evaluation of central dopaminergic systems in parkinsonism.
Collapse
Affiliation(s)
- N Hayase
- Department of Neurosurgery and Nuclear Medicine, Gunma University School of Medicine, Japan
| | | | | | | | | | | |
Collapse
|
15
|
Opacka-Juffry J, Brooks DJ. L-dihydroxyphenylalanine and its decarboxylase: new ideas on their neuroregulatory roles. Mov Disord 1995; 10:241-9. [PMID: 7651438 DOI: 10.1002/mds.870100302] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Recent experimental reports concerning L-dihydroxyphenylalanine (L-DOPA) and aromatic L-amino acid decarboxylase (AADC, L-DOPA decarboxylase) are reviewed in this article. Both in vitro and in vivo data now suggest that L-DOPA is an endogenous neuroactive compound that is released from neurons and acts as a neurotransmitter or neuromodulator in the brain. Administration of exogenous L-DOPA affects dopamine receptor status, AADC activity, and mitochondrial oxidation in experimental animals. The type and severity of these effects depend on the duration of the treatment. These findings may partly explain the limited efficacy of L-DOPA therapy in Parkinson's disease (PD). AADC also plays a controlling role in the central nervous system, being a regulatory enzyme in the synthesis of a putative neuromodulator 2-phenylethylamine and other trace amines. Recent experimental findings on AADC activity and localisation are of importance because they suggest that striatal [18F]DOPA uptake used as an indicator of PD progression in positron emission tomography (PET) studies is likely to overestimate nigrostriatal integrity in advanced PD. Possible new PET tracers of presynaptic dopaminergic function are discussed in this context.
Collapse
|
16
|
DeJesus OT, Murali D, Kitchen R, Endres C, Oakes TR, Shelton SE, Freund L, Houser D, Uno H, Holden JE. Evaluation of 3-[18F]fluoro-alpha-fluoromethyl-p-tyrosine as a tracer for striatal tyrosine hydroxylase activity. Nucl Med Biol 1994; 21:663-7. [PMID: 9234325 DOI: 10.1016/0969-8051(94)90033-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
3-[18F]Fluoro-alpha-fluoromethyl-p-tyrosine (3-F-FMPT) was evaluated as a tracer for CNS tyrosine hydroxylase (TH) activity in rodents and in a rhesus monkey. Results of in vitro experiments using rat striatal homogenates showed that the introduction of fluorine into the 3-phenyl position did not significantly alter the ability of FMPT to act as a TH-activated L-aromatic amino acid decarboxylase (L-AAAD) inhibitor. These studies further showed that 3-F-FMPT-induced L-AAAD inhibition was dose-dependent. Furthermore, striatal homogenates prepared from rats pretreated with the potent TH inhibitor alpha-methyl-p-tyrosine was found to have diminished 3-F-FMPT-induced L-AAAD inhibition. However, despite these promising in vitro results, the biodistribution of this compound in mice showed low brain uptake and fast clearance through the kidneys. A PET study using a Rhesus monkey injected with 3-[18F]F-FMPT confirmed the results obtained in mice, i.e. negligible brain uptake but high localization in the bladder. We conclude that 3-[18F]F-FMPT would not be useful as a tracer for cerebral TH activity.
Collapse
Affiliation(s)
- O T DeJesus
- Department of Medical Physics, University of Wisconsin, Madison 53719, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
King FA, Yarbrough CJ. Studies in neurobiology and aging at the United States National Institutes of health-sponsored regional primate research centers. Am J Primatol 1994; 34:41-50. [PMID: 31936977 PMCID: PMC7159694 DOI: 10.1002/ajp.1350340109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/1993] [Revised: 09/24/1993] [Indexed: 11/07/2022]
Abstract
The seven NIH-sponsored Regional Primate Research Centers conduct a wide variety of studies in the neurosciences and on aging. Monkeys and chimpanzees are investigated to validate the results of research obtained with lower species. In addition, primates are often the only species with the appropriate characteristics for studying a particular health problem or certain behavioral or biological principles. One neurological disorder for which the primate model has proven crucial is Parkinson's disease. The surgical implantation of dopaminergic cells and tissue containing a growth factor has been developed in the primate model, and is now being evaluated clinically in humans with Parkinsonism. In addition to neurological diseases such as Parkinson's, multiple sclerosis, and epilepsy, the visual system is a strong focus of basic and applied research at the Centers. In 1981, two neuroscientists whose basic research on vision with application to pediatric ophthalmology took place in part at the New England Regional Primate Research Center, were honored with the Nobel Prize in Physiology and Medicine. Currently, vision studies at the Yerkes Regional Primate Research Center, for example, focus on myopia, post-surgical treatment of congenital cataracts, adult cataract development and treatment, and laser surgery to correct corneal abnormalities. At the Wisconsin Regional Primate Research Center, the role of diet in visual impairment is evaluated during infancy. Diet is also studied to determine its role in the aging process, and the effects of aging on memory. Further, brain cells and other components of the nervous system in aging are also being investigated at these centers. © 1994 Wiley-Liss, Inc.
Collapse
Affiliation(s)
- F A King
- Yerkes Regional Primate Research Center, Emory University, Atlanta, Georgia
| | - C J Yarbrough
- Yerkes Regional Primate Research Center, Emory University, Atlanta, Georgia
| |
Collapse
|