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  • 1
    Electronic Resource
    Electronic Resource
    Methyl 3β-(4-[125I]Iodophenyl)Tropane-2β-Carboxylate In Vitro Binding to Dopamine and Serotonin Transporters Under “Physiological” Conditions (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Methyl 3β-(4-[125I]iodophenyl)tropane-2β-carboxylate ([123I]β-CIT) is a single photon emission computed tomographic radiotracer for in vivo labeling of dopamine (DA) and serotonin (5-HT) transporters. Single photon emission computed tomographic experiments in nonhuman primates showed that [123I]β-CIT in vivo binding to DA transporters had a much slower washout than binding to 5-HT transporters. This observation was not predicted from previously published in vitro studies. These studies, performed at 22°C in nonphysiological buffer, reported similar affinity of [125I]β-CIT for DA and 5-HT transporters. We now report [125I]β-CIT binding parameters to fresh rat membranes at 22°C and 37°C, in a buffer mimicking the composition of cerebrospinal fluid. At both temperatures, binding to DA transporters was best fit by a twosite model, whereas binding to 5-HT transporters was compatible with one population of sites. At 22°C, [125I]β-CIT showed similar affinity to high-affinity DA (0.39 nM) and 5-HT transporter sites (0.47 nM). Increasing the incubation temperature from 22°C to 37°C reduced binding to DA transporters by 60%, whereas binding to 5-HT transporters was only marginally affected. In vitro kinetic experiments failed to detect significant differences in on or off rates that could explain the observed in vivo kinetics. These experiments thus failed to explain [123 I]β-CIT in vivo uptake kinetics, suggesting the existence of specific factors affecting the in vivo situation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62030978.x
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  • 2
    Electronic Resource
    Electronic Resource
    Pharmacological and Regional Characterization of [3H]LY278584 Binding Sites in Human Brain (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 60 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Binding of [3H]LY278584, which has been previously shown to label 5-hydroxytryptamine3 (5-HT3) receptors in rat cortex, was studied in human brain. Saturation experiments revealed a homogeneous population of saturable binding sites in amygdala (KD= 3.08 ± 0.67 nM, Bmax= 11.86 ± 1.87 fmol/mg of protein) as well as in hippocampus, caudate, and putamen. Specific binding was also high in nucleus accumbens and entorhinal cortex. Specific binding was negligible in neocortical areas. Kinetic studies conducted in human hippocampus revealed a Kon of 0.025 ± 0.009 nM−1 min−1 and a Koff of 0.010 ± 0.002 min−1. The kinetics of [3H]LY278584 binding were similar in the caudate. Pharmacological characterization of [3H]LY278584 specific binding in caudate and amygdala indicated the compound was binding to 5-HT3 receptors. We conclude that 5-HT3 receptors labeled by [3H]LY278584 are present in both limbic and striatal areas in human brain, suggesting that 5-HT3 receptor antagonists may be able to influence the dopamine system in humans, similarly to their effects in rodent studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03208.x
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  • 3
    Electronic Resource
    Electronic Resource
    Enantioselectivity of cocaine recognition sites: binding of (1S)- and (1R)-2.beta.-carbomethoxy-3.beta.-(4-iodophenyl)tropane (.beta.-CIT) to monoamine transporters (1993)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 36 (1993), S. 1914-1917 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00065a014
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  • 4
    Electronic Resource
    Electronic Resource
    Coupling efficiency of brain β-adrenergic receptors to Gs protein in suicide, alcoholism and control subjects (1999)
    Springer
    Psychopharmacology 145 (1999), S. 31-38 
    Details
    ISSN: 1432-2072
    Keywords: Key words Brain ; β-Adrenergic receptor ; Alcoholism ; Suicide ; Gs protein ; Coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Abnormal β-adrenergic receptor (βAR) density in the brains of suicide victims has been reported, although results of studies are inconsistent. Ethanol modifies βAR-mediated signal transduction. Moreover abnormal βAR function has been implicated in alcoholism. βAR antagonists, which were used as ligands in previous βAR binding studies, also bind to 5-HT1B/1Dβ receptors; hence, their estimates of βAR density are confounded by binding to 5-HT1B/1Dβ receptors. More importantly, previous studies did not examine βAR agonist affinity or coupling efficiency to Gs protein. We investigated agonist affinity and coupling efficiency of βAR to Gs protein in the brains of ten suicide victims, six subjects with alcoholism, and eight controls. There were no differences in βAR density in either the frontal cortex or hippocampus of suicide victims or alcoholic subjects compared to controls. Preliminary results indicate βAR supercoupling in suicide victims in both brain regions and uncoupling in alcoholic subjects in the frontal cortex. These results are discussed in view of the existing literature on the role of βAR in suicide and alcoholism and the mechanism of action of antidepressants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130051029
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of [123I]ß-CIT and [123I]IPCIT as single-photon emission tomography radiotracers for the dopamine transporter in nonhuman primates (1995)
    Springer
    European journal of nuclear medicine 22 (1995), S. 4-11 
    Details
    ISSN: 1619-7089
    Keywords: Dopamine transporter ; 2β-Carbomethoxy3β-(4-iodophenyl)tropane ; Carboisopropoxy-3β-(4-iodophenyl)tropane ; Single-photon emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Single-photon emission tomographic (SPET) imaging with the radiotracer [123I]2β-carbomethoxy-3β-(4-iodophenyl)tropane ([123I]β-CIT) has been reported to be a useful in vivo measure of dopamine (DA) transporters. However, in addition to its high DA transporter affinity,β-CIT also binds with high affinity to serotonin (5-HT) transporters. 2β-Carboisopropoxy-3β-(4-iodophenyl)tropane (IPCIT) has been demonstrated by in vitro studies to have higher selectivity for the DA transporter. We compared [123I]β-CIT and [123I]IPCIT SPET imaging and plasma metabolite analyses in baboons to evaluate the potential advantages of [123I]IPCIT for quantitative in vivo measurements of DA transporter densities. Both tracers had low levels (2% of total plasma123I activity) of lipophilic radiolabeled metabolites at 420 min. [123I]IPCIT had significantly higher binding to plasma proteins. The average percent free (nonprotein bound) [123I]β-CIT and [123I]IPCIT were 52%±7% and 14%±6%, respectively. Region of interest uptake data were normalized by injected dose and body weight. Consistent with the high density of 5-HT transporters in the midbrain and the lower 5-HT transporter affinity of IPCIT, the normalized peak specific midbrain uptake of [123I]β-CIT (1.7±0.5) was higher than that of [123I]IPCIT (0.4±0.2). Consistent with its greater lipophilicity, [123I]IPCIT had higher nonspecific uptake, such that normalized cerebellar uptake of [123I]IPCIT was about twice that of [123I]β-CIT. The ratio of specific to nonspecific uptake in striatum was greater for [123I]β-CIT compared to [123I]IPCIT; however, striatal binding potentials and distribution volumes were not significantly different. In conclusion, [123I]IPCIT demonstrated in vivo a higher DA transporter selectivity and higher level of nonspecific uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00997241
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  • 6
    Electronic Resource
    Electronic Resource
    Modelling: when and why? (1999)
    Springer
    European journal of nuclear medicine 26 (1999), S. 571-572 
    Details
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002590050423
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