The MT1 receptor as the target of ramelteon neuroprotection in ischemic stroke

Stroke is the leading cause of death and disability worldwide. Novel and effective therapies for ischemic stroke are urgently needed. Here, we report that melatonin receptor 1A (MT1) agonist ramelteon is a neuroprotective drug candidate as demonstrated by comprehensive experimental models of ischemic stroke, including a middle cerebral artery occlusion (MCAO) mouse model of cerebral ischemia in vivo, organotypic hippocampal slice cultures ex vivo, and cultured neurons in vitro; the neuroprotective effects of ramelteon are diminished in MT1-knockout (KO) mice and MT1-KO cultured neurons. For the first time, we report that the MT1 receptor is significantly depleted in the brain of MCAO mice, and ramelteon treatment significantly recovers the brain MT1 losses in MCAO mice, which is further explained by the Connectivity Map L1000 bioinformatic analysis that shows gene-expression signatures of MCAO mice are negatively connected to melatonin receptor agonist like Ramelteon. We demonstrate that ramelteon improves the cerebral blood flow signals in ischemic stroke that is potentially mediated, at least, partly by mechanisms of activating endothelial nitric oxide synthase. Our results also show that the neuroprotection of ramelteon counteracts reactive oxygen species-induced oxidative stress and activates the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. Ramelteon inhibits the mitochondrial and autophagic death pathways in MCAO mice and cultured neurons, consistent with gene set enrichment analysis from a bioinformatics perspective angle. Our data suggest that Ramelteon is a potential neuroprotective drug candidate, and MT1 is the neuroprotective target for ischemic stroke, which provides new insights into stroke therapy. MT1-KO mice and cultured neurons may provide animal and cellular models of accelerated ischemic damage and neuronal cell death.

Preoperative tumor embolization

In this article, the authors review general principles and technical details of preoperative embolization of various hypervascular head, neck, and spinal tumors encountered in contemporary neuroendovascular practice. Indications, treatment goals, techniques, outcomes, and complications are discussed, and illustrative case examples are presented.

Low Morbidity Associated With the Use of Nbca Liquid Adhesive for Preoperative Transarterial Embolization of Central Nervous System Tumors

OBJECTIVE

To determine the safety and efficacy of preoperative embolization of central nervous system (CNS) tumors with n-butyl cyanoacrylate (NBCA) liquid adhesive.

METHODS

Over a 6-yr period, 35 consecutive patients (12 women, 23 men; mean age, 42 yr; range, 6 mo to 75 yr) with a CNS tumor underwent preoperative embolization with NBCA. Tumor type, location, endovascular and surgical treatment, percent of tumor embolization, estimated blood loss, and neurological deficits related to embolization were evaluated retrospectively.

RESULTS

One hundred feeding arteries were embolized (mean, 3 vessels/patient). In only one case (3%) a normal artery was inadvertently occluded by the embolization. During follow-up the resulting neurological deficit resolved completely. There were no neurological deficits or inadvertent embolization events in the remaining 34 cases. The mean percent of tumor embolized was 68%, but did not significantly correlate with operative blood loss (Pearson's correlation coefficient, r = 0.049).

CONCLUSION

In experienced hands, CNS tumors can be embolized with NBCA liquid adhesive with a high degree of safety and efficacy. We believe that adroit embolization technique with NBCA and other embolisates should be part of the contemporary neuroendovascular armamentarium.

A positron emission tomographic study of auditory localization in the congenitally blind

We have used positron emission tomography (PET) to measure regional cerebral blood flow (rCBF) in sighted and congenitally blind subjects performing auditory localization tasks. During scanning, the spectral and binaural cues of localized sound were reproduced by a sound system and delivered via headphones. During tasks that required auditory localization both the sighted and blind subjects strongly activated posterior parietal areas. In addition, the blind subjects activated association areas in the right occipital cortex, the foci of which were similar to areas previously identified in visual location and motion detection experiments in sighted subjects. The blind subjects, therefore, demonstrated visual to auditory cross-modal plasticity with auditory localization activating occipital association areas originally intended for dorsal-stream visual processing. To determine the functional connectivity of pre-selected brain regions in primary and non-primary auditory and posterior parietal cortex in the two cohorts, we performed an inter-regional correlation analysis on the rCBF data set. During auditory localization in the blind subjects, rCBF activity in the right posterior parietal cortex was positively correlated with that in the right occipital region, whereas in sighted subjects correlations were generally negative. There were no significant positive occipital correlations in either cohort when reference regions in temporal or left parietal cortex were chosen. This indicates that in congenitally blind subjects the right occipital cortex participates in a functional network for auditory localization and that occipital activity is more likely to arise from connections with posterior parietal cortex.

A PET study of human auditory spatial processing

To learn more about human auditory spatial processing, we used positron emission tomography (PET) to measure regional cerebral blood flow in human volunteers engaged in sound localization tasks. Spectral and binaural cues of localized sound were reproduced by a sound system and delivered via headphones. During localization tasks, subjects activated inferior parietal lobules (IPL) bilaterally. In a second experiment, matched in design to the first, subjects made non-spatial auditory discriminations based on frequency, activating the IPL bilaterally with left hemispheric predominance. A between-study comparison revealed that the right IPL was significantly more activated during the sound localization task compared with the feature discrimination task, suggesting a preferential role for the right IPL in auditory spatial processing.