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  • 1
    Digitale Medien
    Digitale Medien
    Differential tolerance to cataleptic effects of SCH 23390 and haloperidol after repeated administration (1989)
    Springer
    Psychopharmacology 98 (1989), S. 472-475 
    Details
    ISSN: 1432-2072
    Schlagwort(e): SCH 23390 ; Catalepsy ; Tolerance ; Neuroleptics ; Rat ; Chronic treatment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The development of tolerance to the cataleptic effect of the selective D-1 antagonist SCH 23390 (0.5 mg/kg/day SC or 0.1 mg/kg/day SC) and haloperidol (1 mg/kg/day SC) during repeated administration was investigated. Catalepsy in rats was measured using the horizontal bar method. SCH 23390 induced a dose-related cataleptic effect of short duration, whereas the cataleptic effect of haloperidol appeared more slowly and lasted longer. Marked tolerance to the cataleptic effect of haloperidol developed already 6 days from the beginning of the treatment. The cataleptic effect of the higher dose regimen of SCH 23390 was also significantly reduced after 6 days' treatment. However, unlike haloperidol, this subacute tolerance was gradually reversed and was no longer significant after 12 and 18 days. The cataleptic response to the lower dose of SCH 23390 (0.1 mg/kg/day) was not significantly altered during the treatment and no initial catalepsy tolerance was observed with this dose regimen. These results suggest that different mechanisms are involved in the expression of cataleptic behaviour during chronic treatment with SCH 23390 and classical antipsychotics, such as haloperidol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00441944
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  • 2
    Digitale Medien
    Digitale Medien
    Up-regulation of β1-adrenergic receptors in rat brain after chronic citalopram and fluoxetine treatments (1994)
    Springer
    Psychopharmacology 115 (1994), S. 543-546 
    Details
    ISSN: 1432-2072
    Schlagwort(e): β1-adrenergic receptors ; Rat ; Brain ; Citalopram ; Fluoxetine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Quantitative receptor autoradiography was used to study the effects of the selective serotonin reuptake inhibitors citalopram and fluoxetine and the tricyclic antidepressant imipramine on the regulation of β1-adrenergic receptors in the rat brain. Rats were treated with saline, citalopram (10 mg kg−1), fluoxetine (10 mg kg−1), or imipramine (15 mg kg−1) SC once daily for 14 days. [125I]Iodocyanopindolol binding to β1-adrenergic receptors was found to increase significantly in the caudate-putamen and the somatosensory areas of the frontal cortex after both citalopram and fluoxetine treatments. Imipramine treatment elicited a marked decrease in β1 binding in the outer laminae of the cingulate cortex, as well as in the motor and somatosensory areas of the frontal cortex. In a separate experiment, rats were treated with saline, citalopram (2.5, 10 and 20 mg kg−1) or fluoxetine (2.5, 10 and 20 mg kg−1) SC once daily for 14 days. The effects of citalopram and fluoxetine on β1 receptors in the somatosensory cortex and caudate-putamen were replicated. These results demonstrate that chronic administration of selective serotonin reuptake inhibitors, in contrast to imipramine, can cause a regional up-regulation of β1-adrenergic receptors in the rat brain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02245579
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  • 3
    Digitale Medien
    Digitale Medien
    Striatal D2 dopamine receptor binding characteristics in vivo in patients with alcohol dependence (1994)
    Springer
    Psychopharmacology 116 (1994), S. 285-290 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Alcohol dependence ; Dopamine D2 receptor ; Positron emission tomography ; [11C]raclopride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Striatal D2 dopamine receptor characteristics of nine male patients with alcohol dependence abstinent for 1–68 weeks and eight healthy male volunteers were studied in vivo with positron emission tomography. The selective D2 receptor ligand [11C]raclopride and equilibrium model was used for D2 receptor density (Bmax) and affinity (Kd) measurements. A trend for a decreased striatal D2 receptor density and for reduced D2 receptor affinity was observed in patients with alcohol dependence. These parameters were not statistically significantly different between alcoholics and controls, but the ratio between D2 receptor density and affinity (Bmax/Kd or the striatum/cerebellum ratio from the high specific activity scan) was highly significantly lower in alcoholics than that of controls. In conclusion, the low D2 dopamine receptor Bmax/Kd ratio (striatum/cerebellum ratio) indicates that specific aspects of striatal [11C]raclopride binding in vivo are deviant in alcoholics compared to controls. The result is compatible with a reduced avidity of striatal dopamine D2 receptors in alcoholics, which is in line with the idea that D2 dopaminergic mechanisms are involved in the biology of alcohol dependence in man.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02245330
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  • 4
    Digitale Medien
    Digitale Medien
    Effects of lorazepam administration on striatal dopamine D2 receptor binding characteristics in man – a positron emission tomography study (1997)
    Springer
    Psychopharmacology 132 (1997), S. 361-365 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Benzodiazepine ; Lorazepam ; Dopamine ; Positron emission tomography ; Raclopride ; Psychosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Lorazepam is a widely used benzodiazepine class anxiolytic drug. It is known to enhance GABAergic neurotransmission in the brain, but the actions of benzodiazepines on other neurotransmitter systems are largely unknown. We studied the effects of 1 week’s administration with lorazepam (2 mg daily, PO) or placebo on striatal D2 dopamine receptors in four healthy male volunteers using a double-blind randomized cross-over design. D2 receptor density and affinity as well as binding potential (Bmax/Kd) were measured with [11C]-raclopride and positron emission tomography. Although the individual responses varied, lorazepam did not significantly affect D2 receptor binding characteristics, nor did the average effect sizes exceed test-retest variability of the method. In conclusion, the results suggest that striatal D2 dopamine receptor characteristics are not affected by the clinically relevant lorazepam treatment regimen used.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050356
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  • 5
    Digitale Medien
    Digitale Medien
    Deramciclane, a putative anxiolytic drug, is a serotonin 5-HT2C receptor inverse agonist but fails to induce 5-HT2C receptor down-regulation (1998)
    Springer
    Psychopharmacology 136 (1998), S. 99-104 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Deramciclane ; Anxiolytic drug ; 5HT2C ; 5HT2A ; Serotonin receptor ; Receptor regulation ; Inverse agonist
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Deramciclane (EGIS-3886) is a novel anxiolytic agent that binds with high affinity to 5-HT2A/2C receptors. The interactions of deramciclane with the serotonin 5-HT2C receptor were characterized further using receptor phosphoinositide hydrolysis assays and receptor autoradiography. Deramciclane antagonized 5-HT2C receptor mediated 5-HT-stimulated phosphoinositide hydrolysis with an IC50 value of 168 nM. Deramciclane also decreased basal phosphoinositide hydrolysis by up to 33% (EC50 = 93 nM) in a physiological system in the choroid plexus, suggesting that deramciclane possesses inverse agonist properties at this receptor. Administration of single doses of 0.5 mg/kg and 10 mg/kg resulted in a maximal 5-HT2C receptor occupancy of up to 45% and 79%, respectively, in the choroid plexus. Chronic (14 days) treatment with 0.5 mg/kg or 10 mg/kg deramciclane did not alter [125I]DOI (agonist) or [3H]mesulergine (antagonist) binding to 5-HT2C receptors in the choroid plexus compared to saline-treated controls, as determined by quantitative receptor autoradiography. In comparison, the effects of deramciclane on 5-HT2A binding characteristics and receptor occupancy were also studied. Deramciclane treatment resulted in 5-HT2A receptor occupancy of up to 78%, but no significant effect of chronic treatment on 5-HT2A receptor agonist binding levels was found. In conclusion, these data indicate that deramciclane is a 5-HT2C receptor inverse agonist and occupies 5-HT2C receptors during treatment, and that chronic treatment with deramciclane does not lead to 5-HT2C receptor down-regulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050544
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  • 6
    Digitale Medien
    Digitale Medien
    Brain 5-HT2A receptor occupancy of deramciclane in humans after a single oral administration – a positron emission tomography study (1999)
    Springer
    Psychopharmacology 145 (1999), S. 76-81 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Deramciclane fumarate ; Positron emission tomography ; [11C]-NMSP ; Serotonin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Rationale: Deramciclane fumarate is a new 5-HT2A and 5-HT2C receptor antagonist with putative anxiolytic effects. In the present study the binding of deramciclane to serotonin 5-HT2A receptors in frontal cortex of healthy male volunteers was studied using [11C]-N-methyl spiperone ([11C]-NMSP) and positron emission tomography. Methods: The receptor occupancy percentage was assessed by the means of inhibition of [11C]-NMSP from the 5-HT2A receptors in the frontal cortex. Single oral doses of 20, 50 and 150 mg deramciclane were given to three subjects at each dose level (total n = 9). The receptor occupancy was measured before deramciclane and at 3 and 6 h post-dosing except at the 20 mg dose level where only the 3-h measurement was done. The occupancy percentage was calculated with the ratio method using cerebellum as a reference area. Results: Deramciclane inhibited [11C]-NMSP binding dose and concentration dependently. However, deramasciclane inhibited maximally only 52% of the [11C]-NMSP binding in the frontal cortex, indicating a non-5-HT2A receptor binding component of this radioligand in frontal cortex. On average, specific [11C]-NMSP binding cerebellum ratios below 0.355 were not possible to achieve in this population. The 52% inhibition was regarded to represent near 100% 5-HT2A receptor occupancy. The 50 and 90% receptor occupancies were reached at deramciclane plasma concentrations of 21 ng/ml and 70 ng/ml, respectively. Conclusions: Deramciclane penetrates the blood-brain barrier in humans. Deramciclane binds to the 5-HT2A receptors in the frontal cortex in a saturable manner in vivo. Consequently, the increase in deramciclane concentration in plasma above 70 ng/ml will not result in major increase in the 5-HT2A receptor occupancy in the brain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130051034
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  • 7
    Digitale Medien
    Digitale Medien
    Measurement of extrastriatal D2-like receptor binding with [11C]FLB 457 – a test-retest analysis (2000)
    Springer
    European journal of nuclear medicine 27 (2000), S. 1666-1673 
    Details
    ISSN: 1619-7089
    Schlagwort(e): Dopamine Extrastriatal dopamine D2 receptor Positron emission tomography [11C]FLB-457 Reproducibility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract. [11C]FLB 457 is a radioligand for positron emission tomography (PET) that possesses high affinity to D2/D3 receptors. It has been suggested to be useful for quantification of low-density dopamine D2 receptor populations, e.g. in cortical and limbic brain areas. We explored the reproducibility of five methods for measuring extrastriatal D2-like receptor binding potential with [11C]FLB 457. Seven healthy male volunteers were examined twice with [11C]FLB 457 (high specific radioactivity) on the same day, at least 3 h apart. Four brain areas, frontal cortex, nucleus thalamus, temporal cortex and cerebellar cortex, were examined. Binding potentials (BPs) were derived from (1) a target to cerebellum distribution volume ratio, (2/3) two reversible reference tissue compartment models and (4) a transient equilibrium approach. For comparison, BP values were also calculated with the standard three-compartment kinetic model that does not assume a receptor-free reference region. The use of the standard three-compartment model did not result in reproducible BP estimates. The distribution volume (DV) ratio, reference tissue compartment models and the transient equilibrium method all had good to excellent intraclass correlation coefficients (ICCs) in the studied brain areas ranging from 0.56 to 0.93. Absolute variability was also relatively low, ranging from 5.3% to 10.4%. There were no marked differences in the ICC or absolute and relative variability between the four methods based on a reference tissue (cerebellum). In addition, we did not observe systematic differences in the BP between the first and the second scan. These data indicate that the reproducibility of the DV ratio, reference tissue models and the transient equilibrium method is good or excellent. However, each of these methods includes assumptions affecting their validity. Thus, the choice of method will be critically dependent on the purpose of the study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002590000342
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