Rapid 18F-FDG Uptake in Brain of Awake, Behaving Rat and Anesthetized Chicken has Implications for Behavioral PET Studies in Species With High Metabolisms

Dantrolene paradoxically exacerbates short-term brain glucose hypometabolism, hippocampal damage and neuroinflammation induced by status epilepticus in the rat lithium-pilocarpine model

Status epilepticus (SE) is a neurologic emergency characterized by prolonged or rapidly recurring seizures. Increased intracellular calcium concentration ([Ca2+]i) occurring after SE is a key mediator of excitotoxicity that contributes to the brain damage associated with the development of epilepsy. Accumulated evidence indicates that dantrolene, a ryanodine receptor (RyR) blocker may have protective effects against the SE-induced damage. We evaluated whether dantrolene (10 mg/kg, i.p.) administered twice, 5 min and 24 h after the lithium-pilocarpine-induced SE in rats, had neuroprotective effects. Dantrolene by itself had no effects on control rats. However, it exacerbated the signs of damage in rats that underwent SE, increasing brain glucose hypometabolism as measured by PET neuroimaging 3 days after SE. Likewise, the neurohistochemical studies revealed that dantrolene aggravated signs of hippocampal neurodegeneration, neuronal death and microglia-induced neuroinflammation. Besides, the damaging effects were reflected by severe body weight loss. Overall, our results point towards a deleterious effect of dantrolene in the lithium-pilocarpine-induced SE model. Nonetheless, our results are in opposition to the reported neuroprotective effects of dantrolene. Whether the mechanisms underlying [Ca2+]i increase might significantly differ depending on the particularities of the model of epilepsy used and general experimental conditions need further studies. Besides, it is yet to be determined which isoform of RyRs significantly contributes to Ca2+-induced excitotoxicity in the lithium-pilocarpine SE rat model.

Real-time motion-enabling positron emission tomography of the brain of upright ambulatory humans

BACKGROUND

Mobile upright PET devices have the potential to enable previously impossible neuroimaging studies. Currently available options are imagers with deep brain coverage that severely limit head/body movements or imagers with upright/motion enabling properties that are limited to only covering the brain surface.

METHODS

In this study, we test the feasibility of an upright, motion-compatible brain imager, our Ambulatory Motion-enabling Positron Emission Tomography (AMPET) helmet prototype, for use as a neuroscience tool by replicating a variant of a published PET/fMRI study of the neurocorrelates of human walking. We validate our AMPET prototype by conducting a walking movement paradigm to determine motion tolerance and assess for appropriate task related activity in motor-related brain regions. Human participants (n = 11 patients) performed a walking-in-place task with simultaneous AMPET imaging, receiving a bolus delivery of F18-Fluorodeoxyglucose.

RESULTS

Here we validate three pre-determined measure criteria, including brain alignment motion artifact of less than <2 mm and functional neuroimaging outcomes consistent with existing walking movement literature.

CONCLUSIONS

The study extends the potential and utility for use of mobile, upright, and motion-tolerant neuroimaging devices in real-world, ecologically-valid paradigms. Our approach accounts for the real-world logistics of an actual human participant study and can be used to inform experimental physicists, engineers and imaging instrumentation developers undertaking similar future studies. The technical advances described herein help set new priorities for facilitating future neuroimaging devices and research of the human brain in health and disease.

Preclinical Neuropathic Pain Assessment; the Importance of Translatability and Bidirectional Research

For patients suffering with chronic neuropathic pain the need for suitable novel therapies is imperative. Over recent years a contributing factor for the lack of development of new analgesics for neuropathic pain has been the mismatch of primary neuropathic pain assessment endpoints in preclinical vs. clinical trials. Despite continuous forward translation failures across diverse mechanisms, reflexive quantitative sensory testing remains the primary assessment endpoint for neuropathic pain and analgesia in animals. Restricting preclinical evaluation of pain and analgesia to exclusively reflexive outcomes is over simplified and can be argued not clinically relevant due to the continued lack of forward translation and failures in the clinic. The key to developing new analgesic treatments for neuropathic pain therefore lies in the development of clinically relevant endpoints that can translate preclinical animal results to human clinical trials. In this review we discuss this mismatch of primary neuropathic pain assessment endpoints, together with clinical and preclinical evidence that supports how bidirectional research is helping to validate new clinically relevant neuropathic pain assessment endpoints. Ethological behavioral endpoints such as burrowing and facial grimacing and objective measures such as electroencephalography provide improved translatability potential together with currently used quantitative sensory testing endpoints. By tailoring objective and subjective measures of neuropathic pain the translatability of new medicines for patients suffering with neuropathic pain will hopefully be improved.

18F-FDG uptake velocity but not uptake level is associated with progression of carotid plaque

OBJECTIVES

The objective of this study was to evaluate whether baseline ¹⁸F-fluorodeoxyglucose (FDG) uptake is associated with carotid plaque progression.

METHODS

A total of 156 subjects with carotid plaque were enrolled and underwent carotid magnetic resonance imaging (MRI) (at baseline and the 12-month follow-up) and positron emission tomography-computed tomography (PET-CT) (baseline). Carotid plaque progression was evaluated by two indices (the incidence of plaque progression and percentage of plaque increase) with three-dimensional (3D) imaging, while the ¹⁸F-FDG uptake was evaluated by the ¹⁸F-FDG uptake levels and ¹⁸F-FDG uptake velocity. The association between plaque progression and ¹⁸F-FDG uptake was investigated by the trend test and multivariate logistic regression analysis.

RESULTS

Of the 156 subjects, 80 (51.3%) showed carotid plaque progression during the 12-month follow-up. Firstly, no association was found between ¹⁸F-FDG uptake levels and plaque progression. Secondly, significant differences in the incidence of plaque progression were observed among the groups with different uptake velocities, showing a significant decreasing trend ranging from high to intermediate to low (p = 0.002, trend test). After adjusting for covariates, an adequate prediction of the ¹⁸F-FDG uptake velocity for the incidence of plaque progression was revealed (OR = 0.682, p < 0.05). In addition, no association was found between the ¹⁸F-FDG uptake velocity and the percentage of plaque increase in the subjects with plaque progression (p = 0.757, trend test).

CONCLUSIONS

Our findings suggest ¹⁸F-FDG uptake velocity is independently associated with the incidence of carotid plaque progression. Additionally, the ¹⁸F-FDG uptake velocity, as another important parameter of PET-CT, warrants further study in future clinical research.

KEY POINTS

• The¹⁸F-FDG uptake levels were not associated with the carotid plaque progression. • The¹⁸F-FDG uptake velocity could predict the incidence of carotid plaque progression. • The¹⁸F-FDG uptake velocity with related factors warrants more attention in future clinical research.