Kora de Bruin

The Acute and Chronic Effects of MDMA (“Ecstasy”) on Cortical 5-HT2A Receptors in Rat and Human Brain☆

While the pre-synaptic effects of 3,4-methylenedioxymethamphetamine (MDMA) on serotonin (5-HT) neurons have been studied extensively, little is known about its effects on post-synaptic 5-HT2 receptors. Therefore, cortical 5-HT2A receptor densities and 5-HT concentration were studied in MDMA treated rats (10 mg/kg s.c.). Furthermore, 5-HT2A post-synaptic receptor densities in the cerebral cortex of recent as well as ex-MDMA users were studied using [123I]R91150 SPECT. In rats we observed a decrease followed by a time-dependent recovery of cortical 5-HT2A receptor densities, which was strongly and positively associated with the degree of 5-HT depletion. In recent MDMA users, post-synaptic 5-HT2A receptor densities were significantly lower in all cortical areas studied, while 5-HT2A receptor densities were significantly higher in the occipital cortex of ex-MDMA users. The combined results of this study suggest a compensatory upregulation of post-synaptic 5-HT2A receptors in the occipital cortex of ex-MDMA users due to low synaptic 5-HT levels.

The Epidermal Growth Factor-Seven Transmembrane (EGF-TM7) Receptor CD97 Is Required for Neutrophil Migration and Host Defense

The epidermal growth factor-seven transmembrane (EGF-TM7) family is a group of seven-span transmembrane receptors predominantly expressed by cells of the immune system. Family members CD97, EGF module-containing mucin-like receptor (EMR) 1, EMR2, EMR3, EMR4, and EGF-TM7-latrophilin-related protein are characterized by an extended extracellular region with a variable number of N-terminal EGF-like domains. EGF-TM7 receptors bind cellular ligands as demonstrated by the interaction of CD97 with decay accelerating factor (CD55) and dermatan sulfate. Investigating the effect of newly generated mAb on the migration of neutrophilic granulocytes, we here report for the first time in vivo data on the function of CD97. In dextran sulfate sodium-induced experimental colitis, we show that homing of adoptively transferred neutrophils to the colon was significantly delayed when cells were preincubated with CD97 mAb. The consequences of this defect in neutrophil migration for host defense are demonstrated in a murine model of Streptococcus pneumoniae-induced pneumonia. Mice treated with CD97 mAb to EGF domain 1 (1B2) and EGF domain 3 (1C5) displayed a reduced granulocytic inflammatory infiltrate at 20 h after inoculation. This was associated with a significantly enhanced outgrowth of bacteria in the lungs at 44 h and a strongly diminished survival. Together, these findings indicate an essential role for CD97 in the migration of neutrophils.

Use of amphetamine by recreational users of ecstasy (MDMA) is associated with reduced striatal dopamine transporter densities: a [123I]β-CIT SPECT study – preliminary report

Abstract.Rationale: Tablets sold as ecstasy often contain not only 3,4-methylenedioxymethamphetamine (MDMA) but other compounds well known to cause dopaminergic neurotoxicity, such as (meth)amphetamine. Furthermore, the use of ecstasy in the Netherlands is often combined with the use of amphetamine. However, little is known about the effects of ecstasy use or the combination of ecstasy and amphetamine use on dopamine (DA) neurones in the human brain. Objectives: This study was designed to investigate the effects of ecstasy as well as the combined use of ecstasy and amphetamine on the density of nigrostriatal DA neurones. Methods: [123I]β-CIT SPECT was used to quantify striatal DA transporters. Striatal [123I]β-CIT binding ratios of control subjects (n=15) were compared with binding ratios of ecstasy users (n=29) and individuals with a history of combined ecstasy and amphetamine use (n=9) after adjustment for age. Results: Striatal [123I]β-CIT binding ratios were significantly lower in combined ecstasy and amphetamine users compared to sole ecstasy users (6.75 versus 8.46, respectively: –20.2%, P=0.007). Binding ratios were significantly higher in ecstasy users when compared to controls (8.46 versus 7.47, respectively: +13.2%, P=0.045). Conclusions: These initial observations suggest that the sole use of ecstasy is not related to dopaminergic neurotoxicity in humans. In contrast, the reported use of amphetamine by regular users of ecstasy seems to be associated with a reduction in nigrostriatal DA neurones.

Pinhole SPECT imaging of dopamine transporters correlates with dopamine transporter immunohistochemical analysis in the MPTP mouse model of Parkinson's disease.

The in vivo analysis of dopaminergic degeneration in animal models of Parkinsons disease (PD), using pinhole single photon emission computed tomography (SPECT), ideally should afford a serial study design, enabling the analysis of the degenerative process as well as the potential neuroprotective and/or restorative properties of drugs over time in living animals. Previously, we demonstrated that striatal dopamine transporter (DAT) levels in rats could be analyzed reproducibly, using pinhole SPECT with the DAT probe [(123)I]N-omega-fluoropropyl-2beta-carbomethoxy-3beta-{4-iodophenyl}nortropane (FP-CIT). However, the capacity of this approach to accurately detect a range of striatal DAT levels in the most widely used animal model of PD, i.e., the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mouse, remains to be determined. For this purpose, various levels of DAT were induced by treating c57BL/6J mice for 1, 3, or 5 days with MPTP (25 mg/kg ip), respectively. [(123)I]FP-CIT SPECT scans were performed 5 days after the last MPTP injection. Mice were perfused 6 days after the last MPTP injection, and the SPECT data were compared to ex vivo striatal and nigral DAT levels as measured by immunohistochemistry within the same animals. The analysis of striatal DAT levels using SPECT and DAT immunohistochemistry yielded highly comparable results on the percentage of DAT reduction in each MPTP group. The in vivo data showed a decrease of specific striatal to non-specific binding ratios by 59%, 82%, and 76% in mice treated for 1, 3, and 5 days, respectively. Moreover, a strong, positive correlation was observed between the in vivo and ex vivo parameters. The present study provides the first evidence that [(123)I]FP-CIT pinhole SPECT allows the accurate detection of a range of striatal DAT (i.e., losses of approximately 60-80%) levels in mice. Since such large dopaminergic lesions could be detected, this SPECT method may at least be useful for analyzing neuroprotective treatment with a clear-cut positive (i.e., complete protection) or negative (i.e., not any protection) effect. Whether this method is also useful for analyzing more subtle effects of neuroprotective treatment (partial protection) remains to be established, by studying mice with small dopaminergic lesions.

Early inflammatory response during the development of right ventricular heart failure in a rat model

Inflammatory activation plays an important role in the pathogenesis and progression of left ventricular (LV) heart failure. In right ventricular (RV) heart failure, little is known about the role of inflammatory activation. We aimed to study the role of inflammatory activation in RV heart failure by serial monitoring during disease progression.

Free-choice and no-choice high-fat diets affect striatal dopamine D2/3 receptor availability, caloric intake, and adiposity.

Different types of high‐fat (HF) diets are used to study diet‐induced obesity (DIO) in rodents and this has led to different phenotypes. This study assesses whether different HF diets differentially affect striatal dopamine D2/3 receptor (DRD2/3) availability, as decreased striatal DRD2/3 availability has been implicated in obesity in relation to reward deficiency for food. Thirty rats were randomized to either a free‐choice HF diet (HF‐choice), a premixed HF diet (HF‐no‐choice), or a standard chow diet for 28 days. Striatal DRD2/3 was measured using 123I‐IBZM storage phosphor imaging at day 29. DRD2/3 availability was significantly decreased in the dorsal striatum in the HF‐choice rats compared to chow rats, but not in HF‐no‐choice rats. Additionally, caloric intake of the HF‐choice rats was significantly higher than that of HF‐no‐choice rats and serum leptin and percentage abdominal fat store weight of total body weight were significantly higher in the HF‐choice rats compared to chow rats. These preliminary results suggest that the choice element in HF diets, which is possibly related to the motivational aspects of eating, leads to overconsumption and to a distinct state of obesity. These results are relevant for future studies on DIO when considering choice of diet type.

[123I]FP-CIT binding in rat brain after acute and sub-chronic administration of dopaminergic medication

Abstract.The recently developed radioligand [123I]FP-CIT is suitable for clinical single-photon emission tomography (SPET) imaging of the dopamine (DA) transporter in vivo. To date it has remained unclear whether dopaminergic medication influences the striatal [123I]FP-CIT binding. The purpose of this study was to investigate the influence of this medication on [123I]FP-CIT binding in the brain. We used an animal model in which we administered dopaminomimetics, antipsychotics and an antidepressant. In vivo [123I]FP-CIT binding to the DA and serotonin transporters was evaluated after sub-chronic and acute administration of the drugs. The administered medication induced small changes in striatal [123I]FP-CIT binding which were not statistically significant. As expected, the DA reuptake blocker GBR 12,909 induced a significant decrease in [123I]FP-CIT binding. [123I]FP-CIT binding in the serotonin-rich hypothalamus was decreased only after acute administration of fluvoxamine. The results of this study suggest that dopaminergic medication will not affect the results of DA transporter SPET imaging with [123I]FP-CIT.

The stereoisomers of 17α-[123I]iodovinyloestradiol and its 11α-methoxy derivative evaluated for their oestrogen receptor binding in human MCF-7 cells and rat uterus, and their distribution in immature rats

We studied the potential of both stereoisomers of 17α-[123I]iodovinyloestradiol (E- andZ-[123I]IVE) and of 11β-methoxy-17α-[123I]iodovinyloestradiol (E-andZ-[123I]MIVE) as suitable radioligands for the imaging of oestrogen receptor(ER)-positive human breast tumours. The 17α-[123I]iodovinyloestradiols were prepared stereospecifically by oxidative radio-iododestannylation of the corresponding 17α-tri-n-butylstannylvi-nyloestradiol precursors. Competitive binding studies were performed in order to determine the relative binding affinity (RBA) of the unlabelled 17α-iodovinyloes-tradiols for the ER in both human MCF-7 breast tumour cells and rat uterine tissue, compared with that of diethylstilboestrol (DES). Target tissue uptake, retention and uptake selectivity of their123I-labelled analogues were studied in immature female rats. All four 17α-iodovi-nyloestradiols showed high affinity for the ER in human MCF-7 cells, as well as rat uterus. Their RBA for the ER showed the following order of decreasing potency: RBA of DES >Z-IVE >Z-MIVE >E-MIVE ≥E-IVE. Neither of these 17α-iodovinyloestradiols showed any significant binding to the sex hormone binding globulin in human plasma. The biodistribution studies showed ER-mediated uptake in the uterus, ovaries and pituitary, that ofE- andZ-[123I]MIVE being higher than that ofE- andZ-[123I]IVE. High target-to-non-target tissue uptake ratios, especially at longer periods after injection (up to 24 h), were exhibited by both isomers of [123I]MIVE. The uterus-to-blood uptake ratio was higher forE-[123I]MIVE. However, the uterus-to-fat uptake ratio appeared to be higher for theZ-isomer of [123I]MIVE, especially at 24 h after injection. Metabolic properties and temperature effects, which play a more important role in vivo, probably cause the discrepancies seen between in vitro and in vivo binding results. On the basis of their in vitro binding properties and in vivo distribution characteristics we conclude thatE- andZ-[123I]MIVE could be suitable radioligands for the diagnostic imaging of ER in human breast cancer. Therefore, further studies with these radioligands in mature normal and tumour-bearing rats are warranted.

In vitro and ex vivo storage phosphor imaging of short-living radioisotopes.

Storage phosphor imaging may be of value for biodistribution studies of short-living radiotracers in small animals. Efficiency, sensitivity and resolution of imaging plates for short-living radioisotopes vary considerably but linear response to many radioisotopes was shown previously. However, these properties have not been compared directly for larger series of short-living radioisotopes, and only few studies have directly compared data obtained from phosphor images of tissue slices with results from dissection biodistribution studies. Therefore, we evaluated the properties of imaging plates for 11 short-living radioisotopes (18F, 32P, 67Ga, 89Sr, (99m)Tc, 90Y, 111In, 123I, 125I, 131I and 201Tl). We also evaluated the biodistribution of [123I]FP-CIT in rat brain using both the phosphor technique and conventional dissection methods. The imaging system showed a linear response for all tested radioisotopes over a wide range of radioactive concentrations and the efficiency, sensitivity and resolution varied greatly for the tested radioisotopes. Shielding experiments revealed the contribution of the various emission products of radioisotopes to these properties. However, quantitative biodistribution studies with radiotracers that are labeled with all tested radioisotopes, even 123I, are feasible. The results from the ex vivo biodistribution study, using [123I]FP-CIT as a radiotracer were similar for the phosphor imaging technique as compared to the dissection technique. Advantages of phosphor imaging in radiotracer distribution studies in rat brain as compared to dissection experiments may be more precise measurements, possibility to reanalyze imaging data and 3D-reconstruction. In conclusion, phosphor imaging is an attractive alternative for biodistribution studies of short-living radiotracers in small animals.

99mTc-GSA Scintigraphy with SPECT for Assessment of Hepatic Function and Functional Volume During Liver Regeneration in a Rat Model of Partial Hepatectomy

Small-animal models are crucial to gain insights in the complex recovery mechanisms of liver function during liver regeneration. 99mTc-Mebrofenin hepatobiliary scintigraphy (HBS) has been introduced for noninvasive assessment of liver function in the clinical setting as well as in experimental research. However, HBS is restricted to planar modalities in small animals because hepatic kinetics are generally too fast for SPECT acquisition. 99mTc-DTPA-galactosyl serum albumin (where DTPA is diethylenetriaminepentaacetic acid) (99mTc-GSA) scintigraphy is an alternative, receptor-mediated, noninvasive liver function test. After hepatic uptake, 99mTc-GSA remains trapped in the liver, which readily enables additional SPECT for the assessment of both liver function and liver functional volume within one test. In this study we evaluated the use of 99mTc-GSA scintigraphy combined with SPECT for the assessment of liver function and liver functional volume in normal and regenerating rat livers. Methods: The reproducibility of 99mTc-GSA scintigraphy and SPECT was investigated by repeated measurements within the same rat. For the assessment in a regenerating liver, 99mTc-GSA scintigraphy with SPECT was performed on 1, 3, 5, and 7 d (n = 6 rats per time point) after 70% partial hepatectomy (PH). Results: The correlation between repeated 99mTc-GSA measurements was strong (r = 0.75, P = 0.019). In normal rat livers, there was a strong, significant correlation between liver functional volume and conventional liver volume (r = 0.93; < 0.0001). The correlation between 99mTc-GSA uptake and liver volume was moderate (r = 0.62, P = 0.043). During the regeneration process, 99mTc-GSA uptake was significantly lower compared with both liver volume (P < 0.001) and liver functional volume (P < 0.001), when expressed as a percentage of baseline levels. There was a strong correlation between liver functional volume and conventional liver volume in the regenerating liver (r = 0.92, P < 0.0001). Conclusion: 99mTc-GSA scintigraphy combined with SPECT is a feasible, noninvasive method to assess hepatic functional volume in normal rat liver as well as in the regenerating rat liver. However, the hepatic 99mTc-GSA uptake as a liver function test seems to underestimate hepatic regeneration in comparison to liver volume.