S. Jovkar

Bio: S. Jovkar is an academic researcher from Max Planck Society. The author has contributed to research in topics: Dopamine receptor & Dopaminergic. The author has an hindex of 2, co-authored 2 publications receiving 58 citations.

PET studies of dopamine receptor distribution using [18F]fluoroethylspiperone: findings in disorders related to the dopaminergic system.

Abstract: PET studies of dopamine D2-receptor binding were performed in thirty patients with various disorders related to the dopaminergic system and in six healthy controls. Uptake of [18F]fluoroethylspiperone in caudate over three hours was analyzed in terms of several indices of receptor binding:caudate-to-cerebellum activity ratio, concentration of ligand as percentage of injected dose, caudate-to-blood radioactivity ratio, slope of tracer uptake curves, binding potential, kinetic constants of a three compartment model. In 14 patients brain glucose metabolism was also measured. Data on medicated patients demonstrate that the average values of most of the above parameters indicate the decreased number of available D2-receptors whereby, besides an age dependent decline, the caudate-to-cerebellum ratio affords the relatively best distinction among diagnostic groups. In individual cases, large variability among subjects permits only the classification of severe pathologies. Morphological damage and neuronal loss in the striatum may also cause abnormal low values both for the indices of receptor binding and for glucose consumption, thus providing a possible pathogenetic link between receptor dysfunction and impaired energy metabolism.

The quantitative analysis of D2-dopamine receptors in baboon striatum in vivo with 3-N-[2'-18F]fluoroethylspiperone using positron emission tomography.

Abstract: We used the ligand 3-N-[2'-18F]fluoroethylspiperone (FESP), which binds to D2-dopamine receptors in the striatum, and positron emission tomography (PET) to quantify striatal D2-dopamine densities (...

Striatal D2 receptor status in patients with Parkinson's disease, striatonigral degeneration, and progressive supranuclear palsy, measured with 11C‐raclopride and positron emission tomography

Abstract: Equilibrium striatal: cerebellar 11C-raclopride (RAC) uptake ratios reflect the density of striatal dopamine D2 binding sites. Using positron emission tomographic scanning we have measured striatal RAC uptake in 6 untreated patients with Parkinson's disease (PD), 5 chronically treated patients with PD and a fluctuating response to L-dopa, 10 patients with striatonigral degeneration (SND), and 9 patients with progressive supranuclear palsy (PSP). Regional cerebral blood flow was determined also, with C15O2. Mean strital: cerebellar RAC uptake was not significantly different from normal in untreated patients with PD, though 2 of these 6 patients showed significantly increased putamen tracer binding. Mean caudate and putamen: cerebellar RAC uptake ratios of the group with PD and fluctuating response to L-dopa were significantly reduced by 30% and 18%, respectively. The patients with SND had lesser, but significant, 10% and 11% decreases in mean caudate and putamen: cerebellar RAC uptake ratios, respectively, whereas patients with PSP showed 24% and 9% reductions in caudate and putamen: cerebellar RAC binding. Striatal and frontal blood flow were significantly reduced in patients with PSP, but not in patients with PD or SND. In conclusion, striatal D2 binding potential is normal or raised in untreated patients with PD, but reduced in patients with PD and a fluctuating response to L-dopa. Patients with SND and PSP show a decrease in striatal RAC binding, but to a lesser extent than patients with PD and a fluctuating response to treatment. Failure of patients with SND and PSP to respond well to L-dopa cannot therefore be due to losss of striatal D2 sites alone, but must reflect loss of other basal ganglia connections.

Effect of Age on D2 Dopamine Receptors in Normal Human Brain Measured by Positron Emission Tomography and 11C-Raclopride

Abstract: • Human postmortem and animal experimental results suggest a decline of the cerebral dopaminergic neuronal system with age. In this study, the radiotracer carbon 11-labeled-raclopride and positron emission tomography were applied to determine the effect of age on striatal D 2 dopamine receptors in 32 healthy volunteer subjects (age range, 21 to 68 years; median, 31 years). An index of specific 11 C-raclopride binding was calculated for putamen, caudate nucleus, and other brain regions in each subject. A significant decrease with age of the index for specific tracer uptake was found in putamen and caudate nucleus. The decrease was steep until 30 years, but slower afterward. After approximately 30 years of age, the decline of specific 11 C-raclopride binding in putamen was found to be 0.6% per year. Our results suggest that D 2 dopamine receptor binding sites (mainly postsynaptically located) decrease as a consequence of normal aging in parallel with the decline of the presynaptic nigrostriatal dopaminergic neuronal system.

Imaging dopamine receptors in the human brain by positron tomography

Abstract: Neurotransmitter receptors may be involved in a number of neuropsychiatric disease states. The ligand 3-N-[11C]methylspiperone, which preferentially binds to dopamine receptors in vivo, was used to image the receptors by positron emission tomography scanning in baboons and in humans. This technique holds promise for noninvasive clinical studies of dopamine receptors in humans.

Effect of reserpine-induced depletion of synaptic dopamine on [11C]raclopride binding to D2-dopamine receptors in the monkey brain.

Abstract: Positron emission tomography was used to examine the in vivo binding of [11C]raclopride to D2-dopamine (DA) receptors in the striatum of two Cynomolgus monkeys after a single dose of reserpine (1 mg/kg, i.v.). A Scatchard procedure was repeated five times to follow D2 receptor density and apparent affinity for 7 weeks after reserpine. Reserpine-induced depletion of DA lead to a marked increase in [11C]raclopride binding, which was still detectable 20 days after treatment. Scatchard analyses indicated that the measured increase in [11C]raclopride binding reflected an increase in receptor affinity but no evident change in receptor density (Bmax). Thus, the increase in [11C]raclopride binding after reserpine should correspond to a reduced competition with endogenous DA for binding to D2 receptors. The results were used to estimate the DA-induced D2 occupancy to be about 40% at physiological conditions. Synapse 25:321–325, 1997. © 1997 Wiley-Liss, Inc.