GABA is the primary inhibitory neurotransmitter in the mammalian brain. So far, little is known about the effects of GABAergic neurotransmission on resting state functional connectivity (rs-FC). In the present study, we assessed rs-FC in the rat brain after challenge with the GABAA receptor (R) agonist and antagonist muscimol (MUS) and bicuculline (BIC), respectively. Rs-fMRI measurements were performed on 12 male Wistar rats anaesthetized with a mixture of ketamine (0.45 mg/kg) and xylazine (0.2 mg/kg) in baseline (BAS) and after intraperitoneal injection of MUS (1 mg/kg) and BIC (1 mg/kg). Data were analyzed with both independent component and neural traffic (NT) analysis. The effect sizes of the differences at each voxel in the individual conditions (MUS – BAS, BAS – MUS, BIC – BAS, BAS – BIC) were tested for significance with paired t tests (two-sided, α = 0.05). Comparisons to BAS as well as between agonistic and antagonistic treatment evidenced that activations and deactivations in neocortex, basal ganglia, thalamic nuclei, limbic system and brain stem, along with voxel-wise increases and decreases of NT, shifted between sides or between portions of individual regions in dorsoventral and/or anterioposterior direction. The appearance or disappearance of activations in a specific brain region may be interpreted to reflect, at least in part, elevated and reduced direct GABAAR agonistic and antagonistic action, respectively, in the afferent and efferent connections of the region in question. Apart from the actual synaptic flow of inhibitory neurotransmitter, however, the increase or decrease of NT relative to BAS also reflects the concomitant effects of those neurotransmitters subject to inhibitory GABAergic action. Thereby, the initial point of BAS as well as challenge is the neurochemical condition exerted by the N-methyl d-aspartate receptor antagonistic and α2 adrenoreceptor agonistic action of ketamine and xylazine, respectively.

We assessed the effect of the 5-HT1A receptor (R) antagonist WAY100,635 on motor behaviors, object place learning and the regional levels of dopamine (DA), serotonin (5-HT) and their metabolites in the rat brain. After a single dose of either WAY100,635 (0.4 mg/kg) or vehicle (0.9% NaCl), recognition memory was assessed together with motor/exploratory behaviors. After sacrifice, regional DA, 5-HT and metabolite levels were determined with HPLC. Overall activity and exploratory behavior were reduced by WAY100,635. Object place recognition did not differ between treatments. WAY100,635 promoted DA metabolization (1) by both monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT) in cingulate, caudateputamen, thalamus and cerebellum, (2) solely by MAO in dorsal hippocampus and (3) solely by COMT in ventral hippocampus and brainstem, but suppressed DA metabolization (by both MAO and COMT) in nucleus accumbens. It promoted 5-HT metabolization (by MAO) in cingulate, caudateputamen, dorsal hippocampus and brainstem, but suppressed it in nucleus accumbens, thalamus and cerebellum. WAY100,635 altered activity and exploratory behavior as well as the quantitative relations between the neurotransmitter/metabolite levels in the individual brain regions, by inducing region-specific shifts in the metabolization pathways.

PURPOSE:For understanding the neurochemical mechanism of neuropsychiatric conditions associated with cognitive deficits it is of major relevance to elucidate the influence of serotonin (5-HT) agonists and antagonists on memory function as well dopamine (DA) and 5-HT release and metabolism. In the present study, we assessed the effects of the 5-HT2A receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) and the 5-HT2A receptor altanserin (ALT) on object and place recognition memory and cerebral neurotransmitters and metabolites in the rat. METHODS:Rats underwent a 5-min exploration trial in an open field with two identical objects. After systemic injection of a single dose of either DOI (0.1 mg/kg), ALT (1 mg/kg) or the respectice vehicle (0.9 % NaCl, 50 % DMSO), rats underwent a 5-min test trial with one of the objects replaced by a novel one and the other object transferred to a novel place. Upon the assessment of object exploration and motor/exploratory behaviors, rats were sacrificed. DA, 5-HT and metabolite levels were analyzed in cingulate (CING), caudateputamen (CP), nucleus accumbens (NAC), thalamus (THAL), dorsal (dHIPP) and ventral hippocampus (vHIPP), brainstem and cerebellum with high performance liquid chromatography. RESULTS:DOI decreased rearing but increased head-shoulder motility relative to vehicle. Memory for object and place after both DOI and ALT was not different from vehicle. Network analyses indicated that DOI inhibited DA metabolization in CING, CP, NAC, and THAL, but facilitated it in dHIPP. Likewise, DOI inhibited 5-HT metabolization in CING, NAC, and THAL. ALT facilitated DA metabolization in the CING, NAC, dHIPP, vHIPP, and CER, but inhibited it in the THAL. Additionally, ALT facilitated 5-HT metabolization in NAC and dHIPP. CONCLUSIONS:DOI and ALT differentially altered the quantitative relations between the neurotransmitter/metabolite levels in the individual brain regions, by inducing region-specific shifts in the metabolization pathways. Findings are relevant for understanding the neurochemistry underlying DAergic and/or 5-HTergic dysfunction in neurological and psychiatric conditions.

Both dopamine (DA) and serotonin (5-HT) play key roles in numerous functions including motor control, stress response and learning. So far, there is scarce or conflicting evidence about the effects of 5-HT1A and 5-HT2A receptor (R) agonists and antagonists on recognition memory in the rat. This also holds for their effect on cerebral DA as well as 5-HT release. In the present study, we assessed the effects of the 5-HT1AR agonist 8-OH-DPAT and antagonist WAY100,635 and the 5-HT2AR agonist DOI and antagonist altanserin (ALT) on rat behaviors. Moreover, we investigated their impact on monoamine efflux by measuring monoamine transporter binding in various regions of the rat brain. After injection of either 8-OH-DPAT (3mg/kg), WAY100,635 (0.4mg/kg), DOI (0.1mg/kg), ALT (1mg/kg) or the respective vehicle (saline, DMSO), rats underwent an object and place recognition memory test in the open field. Upon the assessment of object exploration, motor/exploratory parameters and feces excretion, rats were administered the monoamine transporter radioligand N-o-fluoropropyl-2b-carbomethoxy-3b-(4-[123I]iodophenyl)-nortropane ([123I]-FP-CIT; 8.9 ± 2.6 MBq) into the tail vein. Regional radioactivity accumulations in the rat brain were determined post mortem. Compared to the controls, administration of 8-OH-DPAT impaired memory for place, decreased rearing behavior, and increased ambulation as well as head-shoulder movements. DOI administration led to a reduction in rearing behavior but an increase in head-shoulder motility relative to vehicle. Feces excretion was diminished after ALT relative to vehicle. Dopamine transporter (DAT) binding was increased in the caudateputamen (CP), but decreased in the nucleus accumbens (NAC) after 8-OH-DPAT relative to vehicle. Moreover, DAT binding was decreased in the NAC after ALT relative to vehicle. Findings indicate that 5-HT1AR inhibition and 5-HT2AR activation may impair memory for place. Furthermore, results imply associations not only between recognition memory, motor/exploratory behavior and emotionality but also between the respective parameters and the levels of available DA in CP and NAC.

Left ventricular assisting device (LVAD) is a vital mechanical circulatory assist device for patients with end-stage heart disease, serving as either a bridge to transplantation or palliative destination therapy. Yet device infection represents a major lethal complication, warranting a multi-step, complex therapy approach including an urgent device exchange or heart transplantation. Still, timely diagnosis of site and extent of VAD-specific infection for a proper therapy planning poses challenges in regular clinical care. This single-center, retrospective study aimed to evaluate the impact of volumetric PET parameters with different thresholding compared to semiquantitative PET parameters for accurate diagnosis of VAD-specific infection. Seventeen patients (1 female, 16 males; mean age 57 ± 11 years) underwent [18F]FDG imaging for suspected VAD-specific infection between April 2013 and October 2023. Various metabolic and volumetric PET parameters with different thresholding were collected for specific LVAD components including driveline entry point, subcutaneous driveline, pump pocket, inner cannula and outflow tract. Microbiology and clinical follow-up were used as the final diagnosis standard. Nine of eleven patients with VAD-specific infection underwent urgent heart transplantation, and one had a surgical revision of LVAD. Two patients had non-VAD specific infections, and two had non-VAD related infections. Metabolic burden determination using a fixed absolute threshold provided the best outcome compared to relative thresholding or other metabolic SUV parameters. The total metabolic tumor volume (MTV) cutoff value was 9.3 cm3, and the corresponding sensitivity, specificity, accuracy, and AUC were 90.0

Ziel/Aim An accurate early diagnosis of metastasis in equivocal, sub-centimetric, lymph node lesions with a faint PSMA-1007 uptake in PET images with iterative reconstruction (OSEM) represents one of the major challenges in the clinical care of prostate cancer. Point of spread (PSF) reconstruction with TOF substantially improves signal-to-noise ratio or spatial resolution and thus the detectability of smaller lesions due to reduced spill-in/spill-out, partial volume effect, and ultimately increased activity concentration. With this retrospective, proof-of-concept study, we aimed to analyze the impact of the PSF+TOF reconstruction and its specific relation to OSEM reconstruction on the detectability of lymph node metastases by determining the variation of SUVmax.

Background: Several studies indicate, particularly in the case of [18F]PSMA-1007, a relatively high rate of detection of ganglia in PSMA PET imaging. Ganglia are an integral part of the sympathetic portion of the autonomous nervous system. To date, no studies have directly compared [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 ganglionic uptake intra-individually and analyzed the underlying molecular and physical mechanisms of different detection rates. With this monocentric retrospective study, we sought to evaluate the intra-individual physiological ganglion uptake of these different PSMA ligands in evidence-based imaging for prostate cancer. Methods: Our cohort consists of 19 male patients (median age 72 ± 9 with a range of 56–85) with biochemical recurrence of prostate cancer who underwent both [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 PET/CT in our clinic on the same scanner per standard care between March 2015 and March 2022. Tracer uptake was quantified according to maximum standardized uptake value (SUVmax) for both [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 PET/CT scans. Ganglia-to-background ratios (GBRs) were determined to quantify the image contrast through dividing the SUVmax of the ganglia by the background value (SUVmax of blood pool in the descending aorta, fatty tissue, and skeletal muscle in gluteal region). We used descriptive analyses for demographics and tumor characteristics and performed two-way repeated-measures ANOVA (analysis of variance) for SUV metrics including GBR measurements. Results: In total, we examined 101 ganglia with [18F]PSMA-1007 scanning, localized mostly in pairs as stellate, coeliac, and sacral, of which 76 were also detected with [68Ga]Ga-PSMA-11 PET/CT scanning. There was no statistically significant difference in PSMA uptake in terms of SUVmax between [18F]PSMA-1007 and [68Ga]Ga-PSMA-11 (p value: 0.052). In contrast, the comparison of GBRs revealed a higher detectability rate of ganglia with [18F]PSMA-1007 imaging (p < 0.001). Furthermore, a separate comparison of ganglia with respect to their anatomical location also demonstrated statistically significant differences both within and between [18F]PSMA-1007 and [68Ga]Ga-PSMA-11 PET/CT scans. Conclusion: Given the impression of more accentuated [18F]PSMA-1007 uptake in ganglia compared with 68Ga-labelled counterparts, our study demonstrated that the better detectability of ganglia is not due to more intense [18F]PSMA-1007 uptake by these small structures but to much more favorable physical properties of the radionuclide 18F. The most relevant limitations of our study are its retrospective design and the small patient cohort.

Ziel/Aim N-[2-[4-(2-Methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamid-maleat (WAY-100635) und Altanserin (ALT) wirken als 5-HT1A- bzw. 5-HT2A-Rezeptor(R)-Antagonist. In dieser Studie verglichen wir die Wirkung von akut verabreichtem WAY100635 und ALT auf die regionale D2R-Bindung im Gehirn der Ratte.

In the present studies, we assessed the effect of the 5-HT1A receptor (R) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on motor and exploratory behaviors, object and place recognition and dopamine transporter (DAT) and serotonin transporter (SERT) binding in the rat brain. In Experiment I, motor/exploratory behaviors were assessed in an open field after injection of either 8-OH-DPAT (0.1 and 3 mg/kg) or vehicle for 30 min without previous habituation to the open field. In Experiment II, rats underwent a 5-min exploration trial in an open field with two identical objects. After injection of either 8-OH-DPAT (0.1 and 3 mg/kg) or vehicle, rats underwent a 5-min test trial with one of the objects replaced by a novel one and the other object transferred to a novel place. Subsequently, N-o-fluoropropyl-2b-carbomethoxy-3b-(4-[123I]iodophenyl)-nortropane ([123I]FP-CIT; 11 ± 4 MBq) was injected into the tail vein. Regional radioactivity accumulations were determined post mortem with a well counter. In both experiments, 8-OH-DPAT dose-dependently increased ambulation and exploratory head-shoulder motility, whereas rearing was dose-dependently decreased. In the test rial of Experiment II, there were no effects of 8-OH-DPAT on overall activity, sitting and grooming. 8-OH-DPAT dose-dependently impaired recognition of object and place. 8-OH-DPAT (3 mg/kg) increased DAT binding in the dorsal striatum relative to both vehicle and 0.1 mg/kg 8-OH-DPAT. Furthermore, in the ventral striatum, DAT binding was decreased after 3 mg/kg 8-OH-DPAT relative to vehicle. Findings indicate that motor/exploratory behaviors, memory for object and place and regional dopamine function may be modulated by the 5-HT1AR. Since, after 8-OH-DPAT, rats exhibited more horizontal and less (exploratory) vertical motor activity, while overall activity was not different between groups, it may be inferred, that the observed impairment of object recognition was not related to a decrease of motor activity as such, but to a decrease of intrinsic motivation, attention and/or awareness, which are relevant accessories of learning. Furthermore, the present findings on 8-OH-DPAT action indicate associations not only between motor/exploratory behavior and the recognition of object and place but also between the respective parameters and the levels of available DA in dorsal and ventral striatum.

Ziel/Aim 8-OH-DPAT wirkt als 5-HT1A-Agonist. In dieser Studie untersuchten wir die Wirkung von akut verabreichtem 8-OH-DPAT auf das Objekt- und Ortsgedächtnis sowie auf die Dopamintransporter(DAT)-Bindung im Gehirn der Ratte.

Ziel/Aim Lokalrezidive des Prostatakarzinoms (PCa) mit geringer Größe und Nähe zur Urethra und Harnblase (HB) können die frühzeitige Detektion erschweren. Das F-18-PSMA-1007 bietet aufgrund einer geringeren Ausscheidung über die HB Vorteile gegenüber anderen Pendanten. Diese Arbeit analysiert die Lokalrezidivdetektion mittels F-18-PSMA-PET/CT mit Kontrastmittel (KM) und Spätaufnahmen.

Serotonin(5-HT)ergic projections run from the raphe nuclei to dopamin(DA)ergic cells in substantia nigra/ventral tegmental area (SN/VTA) and to the terminal fields of DA neurons in nucleus accumbens, caudateputamen and neocortex. In the present studies, we assessed the effect of the 5-HT1A receptor (R) antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarbox-amide maleate (WAY-100635) on motor and exploratory behaviors and on D2/3R binding in the rat brain with in vivo imaging methods. D2/3R binding was determined in the same animals after systemic application of WAY-100635 (0.4 mg/kg) and 0.9% saline (SAL), respectively, with [123I]IBZM as SPECT ligand. Anatomical information for the delineation of the target regions was obtained with dedicated small animal MRI. Immediately after treatment with WAY-100635 or SAL, motor/exploratory behaviors were assessed for 30 min in two different batches of animals in an open field. WAY-100635 reduced D2/3R binding in caudateputamen, thalamus, frontal cortex, parietal cortex and ventral hippocampus relative to SAL. Network analysis of regional binding data after WAY-100635 yielded positive connections between (1) caudateputamen and substantia nigra/ventral tegmental area, (2) caudateputamen and ventral hippocampus, (3) substantia nigra/ventral tegmental area and parietal cortex, (4) thalamus and dorsal hippocampus and (5) frontal cortex and parietal cortex, which were not present after SAL. Moreover, WAY-100635 decreased parameters of motor activity (overall activity, ambulation duration and frequency) but increased the duration of grooming behavior relative to SAL. The effect on exploration was time-dependent with an early increase and a subsequent decrease of behavioral parameters (rearing duration and frequency, frequency of head-shoulder motility). For WAY-100635, findings imply a region-specificity as well as a time-dependency of DAergic action.

18F-labeled PSMA ligands offer various advantages as PET tracers over 68Ga-labeled PSMA counterparts. Especially, an improved spatial resolution leads to improved detection rates of smaller prostate cancer (PCa) lesions. However, physiological PSMA uptake of ganglia of the sympathetic trunk can be quickly misinterpreted as possible PSMA-positive lymph node metastases. The aim of this retrospective study is to investigate [18F]PSMA-1007 uptake and its intra-individual reproducibility in ganglia of the sympathetic trunk. We retrospectively included 28 consecutive patients (median age 69 ± 9 with a range of 49–90) with biochemical recurrence of PCa who underwent [18F]PSMA-1007 PET/CT scan and, accordingly, a follow-up examination between August 2018 and August 2021. Cervical, coeliac, and sacral ganglia were identified on the iterative PET reconstructions and correlated with CT component. Tracer uptake of ganglia was determined by measuring SUVmax and SUVmean values. Anatomical position of the ganglia in relation to adjacent vertebral bodies were noted. Statistical analyses were conducted using two-way repeated measures ANOVA and descriptive statistics. The highest [18F]PSMA-1007 uptake was found in coeliac ganglia followed by cervical and sacral ganglia. The SUVmax in coeliac ganglia was 3.13 ± 0.85 (follow-up scan 3.11 ± 0.93), in cervical ganglia 2.73 ± 0.69 (follow-up scan 2.67 ± 0.74), and in sacral ganglia 1.67 ± 0.50 (follow-up scan 1.64 ± 0.52). The SUVmean in coeliac ganglia was 2.28 ± 0.64 (follow-up scan 2.28 ± 0.66), in cervical ganglia 1.62 ± 0.43 (follow-up scan 1.61 ± 0.43) and in sacral ganglia 1.15 ± 0.33 (follow-up scan 1.12 ± 0.34). In a given ganglion station, there was no statistically significant difference of SUVmax or SUVmean values between baseline and follow-up scans. The first systematically described physiological [18F]PSMA-1007 uptake in ganglia of the sympathetic trunk showed a low variability of SUVmax or SUVmean and a good intra-individual reproducibility of [18F]PSMA-1007 uptake in follow-up scans. These findings might improve and guide the differentiation of ganglia from possible malignant lesions.

Ziel/Aim F-18-markiertes prostataspezifisches Membranantigen (F-18-PSMA) bietet als PET-Tracer mehrere Vorteile gegenüber Ga-68-PSMA, u.a. verbesserte Ortsauflösung, was besonders bei sehr kleinen Strukturen zur verbesserten Diagnostik führt. Andererseits können kleinste Strukturen mit physiologischer PSMA-Aufnahme, wie prävertebrale Ganglien, schnell mit PSMA-positiven Lymphknotenmetastasen verwechselt werden. Diese Arbeit soll aufzeigen, inwieweit F-18-PSMA in den Ganglien intra-individuell bei PET-Verlaufskontrollen (VK) reproduzierbare quantitative SUV-Werte liefert und damit in Einzelfällen von Lymphknotenmetastasen unterschieden werden kann.

Ziel/Aim 2,5-Dimethoxy-4-iodoamphetamin (DOI) und Altanserin (ALT) wirken als 5-HT2A-Rezeptor(R)-Agonist bzw. -Antagonist. In dieser Studie untersuchten wir die Wirkung von akut verabreichtem DOI und ALT auf das motorisch/exploratorische Verhalten und die D2R-Bindung im Gehirn der Ratte.