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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent experimental literature has revealed that GABAergic interneurons exhibit increased activity prior to seizure onset, alongside additional evidence that such activity is synchronous and may arise abruptly. These findings have led some to hypothesize that this interneuronal activity may serve a causal role in driving the sudden change in brain activity that heralds seizure onset. However, the mechanisms predisposing an inhibitory network toward increased activity, specifically prior to ictogenesis, without a permanent change to inputs to the system remain unknown. We address this question by comparing simulated inhibitory networks containing control interneurons and networks containing hyperexcitable interneurons modeled to mimic treatment with 4-Aminopyridine (4-AP), an agent commonly used to model seizures in vivo and in vitro. Our in silico study demonstrates that model inhibitory networks with 4-AP interneurons are more prone than their control counterparts to exist in a bistable state in which asynchronously firing networks can abruptly transition into synchrony driven by a brief perturbation. This transition into synchrony brings about a corresponding increase in overall firing rate. We further show that perturbations driving this transition could arise in vivo from background excitatory synaptic activity in the cortex. Thus, we propose that bistability explains the increase in interneuron activity observed experimentally prior to seizure via a transition from incoherent to coherent dynamics. Moreover, bistability explains why inhibitory networks containing hyperexcitable interneurons are more vulnerable to this change in dynamics, and how such networks can undergo a transition without a permanent change in the drive. We note that while our comparisons are between networks of control and ictogenic neurons, the conclusions drawn specifically relate to the unusual dynamics that arise prior to seizure, and not seizure onset itself. However, providing a mechanistic explanation for this phenomenon specifically in a pro-ictogenic setting generates experimentally testable hypotheses regarding the role of inhibitory neurons in pre-ictal neural dynamics, and motivates further computational research into mechanisms underlying a newly hypothesized multi-step pathway to seizure initiated by inhibition.
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PMID:Inhibitory Network Bistability Explains Increased Interneuronal Activity Prior to Seizure Onset. 3200 8

The identification of tert-butyl-4-anilinopiperidine-1-carboxylate (4-anilinopiperdine-t-BOC or 4-AP-t-BOC) in many seized falsified 'Xanax' tablets has been reported after being encountered in forensic casework in late 2019 and early 2020 in Ireland. This substance was also detected in a pink powder submitted for analysis in March 2020. The pink powder was part of a larger seizure comprising brown powders which contained morphine or diamorphine (heroin) or a type of counterfeit heroin or heroin adulterant (known as 'bash'). Novel benzodiazepines and other substances are being detected as ingredients in falsified benzodiazepine tablets more frequently on the illicit market. The detection of 4-AP-t-BOC in benzodiazepine tablets is noteworthy and 4-AP-t-BOC is added to the list of adulterants found in benzodiazepine tablets emerging in Europe. The presence of 4-AP-t-BOC in both falsified 'Xanax' and powdered seizures is unusual, and analytical data are presented to assist with the identification of this compound in suspected illicit substances. The presence of 4-AP-t-BOC in the tablets was confirmed using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry analyses, and spectral fragmentation pathways were suggested. To the authors' best knowledge, information about the biological activity of 4-AP-t-BOC is not available. The removal of the t-BOC protecting group yields 4-anilinopiperidine which has been reported to be involved in the synthesis of fentanyl.
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PMID:An unusual detection of tert-butyl-4-anilinopiperidine-1-carboxylate in seizures of falsified 'Xanax' tablets and in items in a suspected heroin seizure submitted by Irish law enforcement. 3256 51

Chronic intermittent hypoxia (CIH) is the most distinct feature of obstructive sleep apnea (OSA), a common breathing and sleep disorder that leads to several neuropathological consequences, including alterations in the hippocampal network and in seizure susceptibility. However, it is currently unknown whether these alterations are permanent or remit upon normal oxygenation. Here, we investigated the effects of CIH on hippocampal spontaneous network activity and hyperexcitability in vitro and explored whether these alterations endure or fade after normal oxygenation. Results showed that applying CIH for 21 days to adult rats increases gamma-band hippocampal network activity and aggravates 4-Aminopyridine-induced epileptiform activity in vitro. Interestingly, these CIH-induced alterations remit after 30 days of normal oxygenation. Our findings indicate that hippocampal network alterations and increased seizure susceptibility induced by CIH are not permanent and can be spontaneously reverted, suggesting that therapeutic interventions against OSA in patients with epilepsy, such as surgery or continuous positive airway pressure (CPAP), could be favorable for seizure control.
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PMID:Chronic intermittent hypoxia transiently increases hippocampal network activity in the gamma frequency band and 4-Aminopyridine-induced hyperexcitability in vitro. 3274 88


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