Thalamic and prefrontal GABA concentrations but not GABAA receptor densities are altered in high-functioning adults with autism spectrum disorder.

The gamma aminobutyric acid (GABA) neurotransmission system has been implicated in autism spectrum disorder (ASD). Molecular neuroimaging studies incorporating simultaneous acquisitions of GABA concentrations and GABAA receptor densities can identify objective molecular markers in ASD. We measured both total GABAA receptor densities by using [18F]flumazenil positron emission tomography ([18F]FMZ-PET) and GABA concentrations by using proton magnetic resonance spectroscopy (1H-MRS) in 28 adults with ASD and 29 age-matched typically developing (TD) individuals. Focusing on the bilateral thalami and the left dorsolateral prefrontal cortex (DLPFC) as our regions of interest, we found no differences in GABAA receptor densities between ASD and TD groups. However, 1H-MRS measurements revealed significantly higher GABA/Water (GABA normalized by water signal) in the left DLPFC of individuals with ASD than that of TD controls. Furthermore, a significant gender effect was observed in the thalami, with higher GABA/Water in males than in females. Hypothesizing that thalamic GABA correlates with ASD symptom severity in gender-specific ways, we stratified by diagnosis and investigated the interaction between gender and thalamic GABA/Water in predicting Autism-Spectrum Quotient (AQ) and Ritvo Autism Asperger's Diagnostic Scale-Revised (RAADS-R) total scores. We found that gender is a significant effect modifier of thalamic GABA/Water's relationship with AQ and RAADS-R scores for individuals with ASD, but not for TD controls. When we separated the ASD participants by gender, a negative correlation between thalamic GABA/Water and AQ was observed in male ASD participants. Remarkably, in female ASD participants, a positive correlation between thalamic GABA/Water and AQ was found.

Loss of Substantia Nigra Hyperintensity at 3.0-T MR Imaging in Idiopathic REM Sleep Behavior Disorder: Comparison with 123I-FP-CIT SPECT.

Purpose To examine whether the loss of nigral hyperintensity (NH) on 3.0-T susceptibility-weighted (SW) magnetic resonance (MR) images can help identify high synucleinopathy risk in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). Materials and Methods Between March 2014 and April 2015, 18 consecutively recruited patients with iRBD were evaluated with 3.0-T SW imaging and iodine 123-2ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane (123I-FP-CIT) single photon emission computed tomography and compared with 18 healthy subjects and 18 patients with Parkinson disease (PD). Two readers blinded to clinical diagnosis independently assessed the images. 123I-FP-CIT uptake ratios were compared by using the Kruskal-Wallis test, and intra- and interobserver agreements were assessed with the Cohen κ. The synucleinopathy conversion according to NH status was evaluated in patients with iRBD after follow-up. Results NH was intact in seven patients with iRBD and lost in 11. The 123I-FP-CIT uptake ratios were comparable between those with intact NH (mean, 3.22 ± 0.47) and healthy subjects (mean, 3.37 ± 0.47) (P = .495). The 123I-FP-CIT uptake ratios in the 11 patients with iRBD and NH loss (mean, 2.48 ± 0.44) were significantly lower than those in healthy subjects (mean, 3.37 ± 0.47; P < .001) but higher than those in patients with PD (mean, 1.80 ± 0.33; P < .001). The intra- and interobserver agreements were excellent (κ > 0.9). Five patients with iRBD and NH loss developed symptoms of parkinsonism or dementia 18 months after neuroimaging. Conclusion NH loss at 3.0-T SW imaging may be a promising marker for short-term synucleinopathy risk in iRBD. © RSNA, 2017 Online supplemental material is available for this article.

Transcranial direct current stimulation to lessen neuropathic pain after spinal cord injury: a mechanistic PET study.

BACKGROUND: It is suggested that transcranial direct current stimulation (tDCS) can produce lasting changes in corticospinal excitability and can potentially be used for the treatment of neuropathic pain. However, the detailed mechanisms underlying the effects of tDCS are unknown. OBJECTIVE: We investigated the underlying neural mechanisms of tDCS for chronic pain relief using [(18)F]-fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET). METHODS: Sixteen patients with neuropathic pain (mean age 44.1 ± 8.6 years, 4 females) due to traumatic spinal cord injury received sham or active anodal stimulation of the motor cortex using tDCS for 10 days (20 minutes, 2 mA, twice a day). The effect of tDCS on regional cerebral glucose metabolism was evaluated by [(18)F]FDG-PET before and after tDCS sessions. RESULTS: There was a significant decrease in the numeric rating scale scores for pain, from 7.6 ± 0.5 at baseline to 5.9 ± 1.8 after active tDCS (P = .016). We found increased metabolism in the medulla and decreased metabolism in the left dorsolateral prefrontal cortex after active tDCS treatment compared with the changes induced by sham tDCS. Additionally, an increase in metabolism after active tDCS was observed in the subgenual anterior cingulate cortex and insula. CONCLUSION: The results of this study suggest that anodal stimulation of the motor cortex using tDCS can modulate emotional and cognitive components of pain and normalize excessive attention to pain and pain-related information.

Synthesis and evaluation of a 18F-labeled 4-ipomeanol as an imaging agent for CYP4B1 gene prodrug activation therapy.

We report the development of a (18)F-labeled 4-ipomeanol (4-IM), which is metabolized by the CYP4B1 enzyme, to image tumors and monitor enzyme-activating anticancer prodrugs. The fluorine-substituted derivative, 1-(3-furyl)-4-hydroxy-5-fluoro-1-pentanone (F-4-IM, 1), was synthesized from 3-furaldehyde. [(18)F]F-4-IM ([(18)F]1) was prepared in 20%-35% radiochemical yield by a fluorine-18 displacement reaction, followed by reduction and deprotection of the ketal group, and was shown to be stable (>96% at 2 hours) in human serum at 37°C. The biodistribution of [(18)F]F-4-IM in normal rats was high in the lung, where CYP4B1 gene is preferentially expressed. We transduced C6-glioma cells with a retrovirus-expressing CYP4B1 (C6-CYP4B1). Evaluation of CYP4B1 expression was confirmed by reverse transcription polymerase chain reaction and MTT assay. Cell assays were carried out using C6 and C6-CYP4B, and the uptake of [(18)F]F-4-IM in these cells was compared with that in parental controls. The uptake ratio of [(18)F]F-4-IM was 2.8-fold higher in C6-CYP4B1 compared with that in parental cells at 1 hour, whereas [(3)H]4-IM was taken up at similar rates in both cell lines after 6 hours. These results suggest that [(18)F]F-4-IM could be a promising PET imaging agent with potential to be used for imaging of CYP4B1-transfected tumor cells, as well as for monitoring CYP4B1 enzyme/prodrug interactions.

Evaluation of Salivary Gland Dysfunction Using Salivary Gland Scintigraphy in Sjögren's Syndrome Patients and in Thyroid Cancer Patients after Radioactive Iodine Therapy.

PURPOSE: Salivary gland scintigraphy (SGS) provides an objective means of diagnosing salivary gland dysfunction in Sjögren's syndrome (SS) patients and in thyroid cancer patients after radioactive iodine (RAI) therapy. In the present study, SGS was performed in SS patients and in thyroid cancer patients post-RAI, and scintigraphic parameters were compared. METHODS: Twenty-eight SS patients (males:females = 1:27, age 53.3 ± 11.9 years), 28 controls (males:females = 3:25, age 54.1 ± 10.1 years), and 92 thyroid cancer patients (males:females = 28:64, age 46.2 ± 12.9) who had undergone a session of high-dose RAI therapy (mean dose, 5.2 ± 1.5 GBq) were included. SGS was performed using Tc-99m pertechnetate (925 MBq). Scintigraphic parameters (parotid uptake ratio PU, submandibular uptake ratio SU, percentage parotid excretion %PE, and percentage submandibular excretion %SE) were measured and compared for SS, thyroid cancer post-RAI, and control patients. RESULTS: PU, SU, %SE, and %PE were all significantly lower in SS than in post-RAI thyroid cancer or control patients (p < 0.05), whereas only %PE was significantly lower in post-RAI thyroid cancer patients than in controls (p < 0.05). SU and %SE were found to be correlated with the unstimulated whole salivary flow rate. CONCLUSION: Scintigraphic parameters derived from SGS can play a crucial role in the detection of salivary gland dysfunction in SS patients and in post-RAI thyroid cancer patients.

Modafinil-induced hippocampal activation in narcolepsy.

This study was undertaken to investigate regional metabolic abnormalities and to determine the effects of modafinil in narcoleptics on cerebral glucose metabolism using [(18)F] fluorodeoxyglucose positron emission tomography (FDG PET). Eight narcoleptic patients participated in the study. Two [(18)F] FDG PET scans were obtained before and after 2 weeks of modafinil treatment. To identify the effect of modafinil on regional cerebral abnormalities in narcoleptics, pre- and post-treatment PET scans were compared using paired t-statistics with voxel-wised manner. In narcolepsy patients, significant decreases in cerebral glucose metabolism were observed in the midbrain and upper pons, bilateral hypothalamus, posterior thalamus, hippocampus and right parahippocampus as compared with healthy subjects. After treatment, a significant increase in glucose metabolism in the left hippocampus was found in comparison with pre-treatment scan. This study demonstrated that modafinil activates the hippocampus which receives the afferents from hypothalamus, the center of sleep-wake rhythm.

Effect of ginseng saponins on enhanced dopaminergic transmission and locomotor hyperactivity induced by nicotine.

Several studies have shown that behavioral hyperactivity induced by psychomotor stimulants is prevented by ginseng saponins. In an attempt to investigate whether the effect of ginseng saponins is through their inhibitory action on the enhanced dopaminergic transmission by psychomotor stimulants, we examined the effects of ginseng total saponin (GTS) presynaptically on nicotine-induced dopamine (DA) release in the striatum of freely moving rats using in vivo microdialysis technique and postsynaptically on the in vitro and in vivo binding of [3H]raclopride to DA D2 receptors. Also, we examined the effects of GTS on nicotine-induced locomotor hyperactivity and on nicotine-induced Fos protein expression in the nucleus accumbens and striatum. Systemic pretreatment with GTS (100 and 400 mg/kg, intraperitoneally (i.p.)) resulted in a dose-dependent inhibition of locomotor hyperactivity induced by nicotine. GTS decreased nicotine-induced DA release in the striatum in a dose-dependent manner. However, GTS had no effects on resting levels of locomotor activity and extracellular DA in the striatum. GTS inhibited the in vitro binding of [3H]raclopride to rat striatal membranes with an IC50 of 5.14+/-1.09 microM. High doses of GTS (400 and 800 mg/kg, i.p.) resulted in decreases in the in vivo binding of [3H]raclopride in the striatum. GTS decreased nicotine-induced Fos protein expression in the nucleus accumbens and striatum, reflecting the inhibition by GTS of nicotine-induced enhancement of dopaminergic transmission. The results of the present study suggest that GTS acts not only on dopaminergic neurons directly or indirectly to prevent nicotine-induced DA release but also postsynaptically by binding to DA D2 receptors. This may explain the blocking effect of GTS on behavioral activation induced by nicotine and conceivably by other psychostimulants. Our data raise the possibility that GTS, by attenuating nicotine-induced enhancement of dopaminergic transmission, may prove to be a useful therapeutic agent for nicotine addiction and warrant further investigation on its effect on nicotine's rewarding property.

Simvastatin inhibits cigarette smoking-induced emphysema and pulmonary hypertension in rat lungs.

RATIONALE: In cigarette smoking-induced chronic obstructive pulmonary disease, structural and functional derangements are characterized by parenchymal destruction and pulmonary hypertension. Statins are 3-hydroxy-3-methyl-glutaryl-coenzyme-A reductase inhibitors that have been used as lipid-lowering agents. These drugs also have additional pharmacologic properties, including antiinflammation, scavenging reactive oxygen species, restoring endothelial function, and antithrombogenesis, all of which can counteract the harmful effects of cigarette smoking. OBJECTIVE: We performed assays to determine whether simvastatin could attenuate lung damage induced by chronic cigarette smoking in rats. METHODS: In Sprague-Dawley rats exposed to cigarette smoke for 16 weeks, morphologic changes in the lungs and pulmonary arterial pressure were examined. MAIN RESULTS: Simvastatin inhibited lung parenchymal destruction and development of pulmonary hypertension, and also inhibited peribronchial and perivascular infiltration of inflammatory cells and induction of matrix metalloproteinase-9 activity in lung tissue. Simvastatin additionally prevented pulmonary vascular remodeling and the changes in endothelial nitric oxide synthase expression induced by smoking. In human lung microvascular endothelial cells, simvastatin increased expression of endothelial nitric oxide synthase mRNA. CONCLUSIONS: Simvastatin ameliorated the structural and functional derangements of the lungs caused by cigarette smoking, partly by suppressing inflammation and matrix metalloproteinase-9 induction and preventing pulmonary vascular abnormality. These findings indicate that statins may play a role in the treatment of cigarette smoking-induced chronic obstructive pulmonary disease.

Synthesis and evaluation of fluorine-substituted 1H-pyrrolo[2,3-b]pyridine derivatives for dopamine D4 receptor imaging.

Seven fluorine-substituted 1H-pyrrolo[2,3-b]pyridine derivatives were synthesized based on a lead ligand, 3-[[4-(4-iodophenyl)piperazin-1-yl]-methyl]-1H-pyrrolo[2,3-b]pyridine (L-750,667) and evaluated as potential dopamine D(4) receptor imaging agents by positron emission tomography (PET). Binding affinities of these ligands for the dopamine D(2), D(3), and D(4) receptor subtypes were measured in vitro. Most ligands showed high and selective binding for the D(4) receptor. Ligand 7 had high affinity for the D(4) receptor, whereas ligands 1, 2, and 6 showed high selectivity for the D(4) receptor. LogP values were calculated for the ligands in this series and ligand 6 had the lowest lipophilicity. (18)F-labeled ligand 7 demonstrated a uniform regional brain distribution and a rapid washout in mice, probably due to nonspecific binding. Based on their in vitro binding properties and calculated logP values, ligand 6 appears to have the most promise for dopamine D(4) receptor imaging.

Serial positron emission tomography findings in a patient with hydrocephalic dementia and Alzheimer's disease.

Comorbidity of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD) is not uncommon. However, few studies have reported the clinical courses of these patients in depth. A 73-year-old woman was confirmed to have AD by a biopsy performed during a shunt operation for NPH after a head trauma. She was followed for 4 years using serial neuropsychological tests and positron emission tomography (PET). Her clinical symptoms remained improved for 2.5 years and then declined. The 1-year minus the presurgical PET scan highlighted the bilateral frontal area, basal ganglia, and thalamus, which may reflect brain regions associated with the improvement of hydrocephalic dementia. On the other hand, the 1-year minus the 4-year scan highlighted the bilateral temporoparietal area and the posterior cingulate gyrus, which may reflect brain regions associated with the aggravation of AD. This subtraction method may be useful for monitoring the clinical course in patients with NPH and AD.